Compressor 2 and 3 have very powerful tools for converting and upscaling video, as well as doing slo-mo. The optical flow technology, which Apple acquired when they bought the powerful compositing application Shake (only later to kill it), is the key to the results that you can get from Compressor. The key to getting the best results is the Frame Controls settings in Compressor.
Compressor is very good at standards conversion or converting video to a different frame rate. People often call this PAL and NTSC conversion although this isn't really accurate, but it will handle the same tasks that systems that do this do--namely the scaling and frame rate conversions. Frame rate conversions in particular are difficult to do really well. There are some standalone products from Teranex that just do this for around $2500 Well Compressor does this really well, but Teranex does it in real-time and Compressor is really slow.
Optical flow can also help in up-conversion of interlaced footage. Interlacing makes it really hard to do upconversion because your vertical resolution is basically split in two. For an example of how to scale things up badly look at what Final Cut Pro does in the timeline. FCP basically throws away half of your vertical resolution as soon as you scale a video clip. So the difference between 100% scale and 99% or 101% scale is crisp video and a blurry messy. When scaled up like this over 200%, not unusual when putting in standard-def footage into a high-def project, fine detail like type also starts shaking up and down from the interlacing--it looks ugly.
Compressor is an improvement on how FCP works in a number of ways. First, it can analyze the image and decide to selectively keep detail from both fields when the video isn't moving--if visuals in a part of a frame is moving, then only that part of the frame will lose resolution. With the optical flow technology, Compressor guesses how a part of the frame is moving and intelligently creates an image with more resolution than other results. These two approaches are handled in the deinterlacing settings in Compressor--the first approach is described as Better while Best uses optical flow.
The Retiming controls are where Compressor handles different frame rates. For example going from 25 fps video from Europe to 30fps video over in North America, usually handled as 60i (interlaced) especially in standard-def. The Better and Best settings in Compressor use optical flow. Like with deinterlacing, optical flow analyzes your video and recognizes object and how they are moving--the optical flow then intelligently creates new frames that move objects smoothly without losing detail. By the way, going from 24fps, which is a progressive format, is not a problem for us folks working in 60i. You can do this right in FCP without any fancy conversion (assuming you want to keep the 24fps filmic look.)
As an example, here's what I recommended to someone doing PAL to NTSC conversion:
Resizing: Better
Deinterlacing: Better (motion adaptive)
Retiming: Better
In this case, the scaling is going down (PAL has more resolution than NTSC, so you should get good results without jumping through a lot of hoops.) I reserved the optical flow use to only retiming at the Better setting. I didn't recommend optical flow on deinterlacing to save time. But if time isn't an issue then using Best for deinterlacing should improve results.
Unfortunately, all this intelligent analysis by optical flow is very processor and time-intensive. So for example using optical flow for retiming and and deinterlacing makes my quad-core G5 slow to a crawl--I'd give a ballpark estimate of 1 minute to process 1 second of video. But if quality is important, then the results can be excellent.
There are some plug-ins that specialize in upconversion, namely InstantHD. Check here for my post on upconversion.
Here are two good articles on using Compressor. Macworld discusses standards conversions here that walks you through the whole process:
Send video abroad
This post at Digital Rebellion gives detailed info on all the settings in Frame Controls.
Using Frame Controls in Compressor
The Macworld article also recommends an interesting workflow using Cinema Tools to convert PAL to NTSC by conforming the PAL to 24fps, scaling and deinterlacing in Compressor, then adding pulldown in FCP. Interesting workflow that I've never seen used.
The Retiming controls in Compressor can also give you some very good slo-mo results. Here are some cool tests done that compares Final Cut Pro versus Compressor at various speeds on two shots.
"Final Cut Studio slow motion demo"
"Final Cut slow motion at various speeds"
The author brings up a good point--if you are shooting a shot to be slo-mo, then shoot at as high a frame rate as you can--60p, 60i, 50p, 50i are good, where 24 fps is bad for slo-mo. The more samples per second of the image you can acquire, the better the slo-mo will work.
Showing posts with label high-definition. Show all posts
Showing posts with label high-definition. Show all posts
Friday, July 25, 2008
Sunday, March 9, 2008
My 2¢ on the Consumer Experience--HDTV, Apple TV, iPhone
Executive Summary of My 2¢: HDTV is great, but there are too many gatekeepers and technology hurdles--the hottest distribution platform in the future could be mobile video. (This post ended up being much longer than I thought it would be.)HDTV
So I bought a high-def TV on Friday. I didn't want a big set that would dominate my studio apartment or cover up windows. So I decided on a 32" set, which is still larger than the 27" set that it is replacing. But once I got to the store and stood back about 8 feet, I was having a hard time distinguishing the advantage of high-def. They have these videos at Best Buy that do a split screen of high-def and a simulated standard-def. Well at 32" and 8 feet, the advantages weren't that great. (I wrote recently about some equations for how screen size and viewing distance effect perceived resolution.) I went with a $900 Sony KDL-32s3000 because it was the set that I could perceive the most difference in high-def that was under a 1K. I found that basic 32" sets weren't as sharp as the more pricey Sony. I wanted to feel like I wasn't just getting a slightly larger, brighter set.
I've watch a decent amount of video so far, and I'm happy with the set. I watched a couple of DVD's and they looked good. The DVD's look much larger because 1/4 of the screen isn't lost to letterboxing as was the case with my old 4:3 tube TV. Road to Perdition was on ABC last night, and it was nice to see a movie in HD. Although sitting through commercials to watch a movie is a hassle, and I don't plan on watching movies this way. PBS had a travel show on Italy, and I was totally absorbed by the Italian coastline in HD.
Old analog TV looks like crap on an HDTV. I used to record a fair amount of TV on a DVD recorder that only had an analog over-the-air tuner. Well when I hooked this recorder up to the HDTV and tried to watch some TV that I recorded, I decided I couldn't watch TV like that. The artifacts from analog TV, like ghosting of the image and noise, look just awful on a high-def display. So I replaced my old DVD recorder with a newer model with digital TV antenna. So far, the clean recordings that I get from the new DVD recorder, a Panasonic DMR-EZ27 look good even though they are standard-def recordings only. The difference in recording a digital standard-def signal is significantly better than an analog TV signal.
So I think I have dissed digital OTA (over the air) TV before. I had an experience a few years ago where I bought a digital tuner and found that I could not get channels reliably. Well my experience this time around has been very good. The digital reception is much better now than my analog reception was. Even my old rabbit-ears antenna works fine.
Apple TV
I have been thinking about getting an Apple TV after plugging it so much. But when it came down to it, I didn't think it was yet worth the $225 price. While it would be great to rent HD movies, there's not that much selection yet. There are almost 100 movies in HD, but it looks like Apple is having a harder time getting movies than they expected. They had promised 1,000 standard-def rental by the end of February. Instead, they had only around 350. It makes me worried that the studios are going to dick around with Apple because they don't want to see Apple TV succeed like the iPod did and become a dominant media platform. Not good news for the Apple TV when they can't even meet their targets for content.
I did go check out the Apple TV at the Apple Store. I thought the HD movie clips looked good although everyone says that Blu-ray leaves it in the dust on a large set. The podcast interface was cool. With the 2.0 software on Apple TV, you don't need to use your computer to download podcasts before watching. You can browse and search podcasts right on your TV, and if their server is fast enough, start watching them immediately. I think it's a pretty good model for media distribution. Unfortunately, until these media extender boxes take off, then there's just not that many boxes out there that will play video podcasts on the TV.
I was able to easily search for our show Mosaic and play it on the Apple TV. Unfortunately, 320x240 looks just awful on an HDTV. Apple has been recommending video podcasts be 640x480 or 640x360 in order to look good on an HDTV. That's about 4 times as many pixels, so much more data to serve/download. But there's something to the idea that you have 1,000's of different podcasts that you can access instantly on your TV set and it is not controlled by gatekeepers like Comcast or AT&T. (Check out this blog post "7 Ways Apple TV Changes The Game And What Podcasters Need To Know And Do About It" for some interesting thoughts on Apple TV and podcasting.)
So when it came down to shelling out $225 for the chance to rent HD movies with Apple TV, it wasn't worth it, even for an Apple fan boy like me. I'm also not ready to spend $400 for a Blu-ray player/PlayStation 3 to watch Blu-ray movies. For the time, I think DVD's look good enough on my set. If the selection takes off on the Apple TV, I'll reconsider.
iPhone
So after buying an HDTV set, I've decided that the real action is on the small-screen. This week was a big week for the iPhone with the announcement of a software developer kit. That means all kinds of third-party applications are going to start appearing for the iPhone. Apple showed off an instant messaging app for AOL. I was skeptical that they would allow IM because that seems like competition for the SMS messaging that AT&T still charges for. I think Apple is really going to open up phones as a great mobile computing platform.
This past week, BBC came out with an iPlayer site that has BBC videos in h.264 Quicktime for the iPhone. Recently it's come out that there's no real chance for Flash on the iPhone--Apple says that the iPhone doesn't have enough computing power to run Flash. Since most sites are encoding videos in Flash, that leaves a pretty big hole for streaming video to the iPhone. BBC decided to start encoding h.264 video just for the iPhone. (YouTube has been doing some h.264 encoding too since the iPhone launch.) BBC's iPlayer is basically a website with a simplified interface that works well on the iPhone's small screen. It only works over WiFi now--the Edge data network is too slow to stream video, but maybe when the iPhone gets on 3G networks streaming video will be better. Oh, no BBC for you--it only works in the United Kingdom. But I think it's interesting to think about mobile distribution of video. Our Mosaic Intelligence Report and Global Pulse would be great for mobile video.
In short my thoughts at the moment are that HDTV is great, but there are too many gatekeepers and technology hurdles--the hottest distribution platform in the future will be mobile video. I think Apple is still playing a positive role for consumers in opening access to content on both the mobile end and on the TV. Maybe I'm too optimistic about mobile--the telco's also control the mobile network and I can't see them being excited about their mobile networks being filled with free videos.
Saturday, February 16, 2008
DV.com on HD Monitoring
"Ten HD Monitors for Desktop and Camera Use" PDF (registration req'd)
A little gear guide from DV.com. I'm most interested in the JVC DT-V1710CGU because 1)it's relatively affordable 2) it's CRT based. CRT is good because it can actually display interlaced images natively and it is the standard for doing color correction. Mike Curtis of HDforIndies recommended it in his editing configurations over at Silverado Systems.
This article also covers some smaller LCD's that are small enough to be mounted on a camera. LCD's are being used in post-production, and this article lays out the competition from Sony, Panasonic, and JVC.
A little gear guide from DV.com. I'm most interested in the JVC DT-V1710CGU because 1)it's relatively affordable 2) it's CRT based. CRT is good because it can actually display interlaced images natively and it is the standard for doing color correction. Mike Curtis of HDforIndies recommended it in his editing configurations over at Silverado Systems.
This article also covers some smaller LCD's that are small enough to be mounted on a camera. LCD's are being used in post-production, and this article lays out the competition from Sony, Panasonic, and JVC.
Saturday, February 2, 2008
High Definition Blogwad
My brother just bought a high-definition TV. Luckily, he didn't ask me for any advice about what kind of TV to get. I don't even own a high-def TV and hardly ever see one unless I'm in an electronics store. Buying a new set is confusing and takes some research to make an informed research.
I came across some stuff from David Pogue of the NY Times and CNBC that I think is a useful quick overview of buying an HDTV set. Seems like good advice for the first-time buyer:
Tech Call: HDTV (Video)
FROM THE DESK OF DAVID POGUE: Clearing Up Some of the Confusion Over HDTV
I'm thinking about taking the plunge, but first I need to make sure I can get some high-def content. Maybe I'll follow up on my pitching for Apple TV and buy one. A couple of years ago I tried to get some over-the-air high-def and was very disappointed with the reception that I got in my apartment. Most of the channels I couldn't get or the signal wasn't reliable enough to watch--in sum, much worse reception than my analog TV could get. A roof antenna is recommended for OTA DTV, but I was at a friend's in DC and he got good reception in his apartment with rabbit ears. The FCC is starting to hand out coupons to get cheap OTA digital receiver boxes. I plan to try OTA digital TV again once the cheap receivers end up in stores.
How big of a screen and what resolution are two of the most basic questions when buying a new set. This article came up with a formula for determining when a higher resolution would be of benefit.
"1080p Does Matter - Here's When (Screen Size vs. Viewing Distance vs. Resolution)"
So for example, I sit about 10 feet from my TV, and I don't really want a TV bigger than 32". According to this article, I will be barely able to perceive the full resolution of 480 progressive lines of video. In order to appreciate the detail of 1080p, I would need to buy a 60" TV, which I think of as an insanely large TV. Well, as a video professional I'd like to think that I could appreciate the difference, but maybe there's no point in getting a high-def TV at all if I'm not committing to a giant TV.
I came across some stuff from David Pogue of the NY Times and CNBC that I think is a useful quick overview of buying an HDTV set. Seems like good advice for the first-time buyer:
Tech Call: HDTV (Video)
FROM THE DESK OF DAVID POGUE: Clearing Up Some of the Confusion Over HDTV
I'm thinking about taking the plunge, but first I need to make sure I can get some high-def content. Maybe I'll follow up on my pitching for Apple TV and buy one. A couple of years ago I tried to get some over-the-air high-def and was very disappointed with the reception that I got in my apartment. Most of the channels I couldn't get or the signal wasn't reliable enough to watch--in sum, much worse reception than my analog TV could get. A roof antenna is recommended for OTA DTV, but I was at a friend's in DC and he got good reception in his apartment with rabbit ears. The FCC is starting to hand out coupons to get cheap OTA digital receiver boxes. I plan to try OTA digital TV again once the cheap receivers end up in stores.
How big of a screen and what resolution are two of the most basic questions when buying a new set. This article came up with a formula for determining when a higher resolution would be of benefit.
"1080p Does Matter - Here's When (Screen Size vs. Viewing Distance vs. Resolution)"
So for example, I sit about 10 feet from my TV, and I don't really want a TV bigger than 32". According to this article, I will be barely able to perceive the full resolution of 480 progressive lines of video. In order to appreciate the detail of 1080p, I would need to buy a 60" TV, which I think of as an insanely large TV. Well, as a video professional I'd like to think that I could appreciate the difference, but maybe there's no point in getting a high-def TV at all if I'm not committing to a giant TV.
Good Techy Info from Quantel and Avid
OK, this post is just stuff that I copied from the Quantel Digital Factbook. It's a ridiculously long post, but Quantel's document is really big, and I would thought it might be helpful for folks to see what I pulled out of it. If you are in to the geeky detail then I recommend looking at the original, which includes some good diagrams that I didn't bother to try and copy. I found out about this document from a Jay Rose column at dv.com (registration req'd.)
Avid has also come out with some good documents that's similar to the Quantel document. It includes a pretty good guide to different video formats--although it misses some new ones like Panasonic's AVC-Intra. It's much more digestible than Quantel's. Like the Quantel, very geeky--topics include sampling, compression, digital film, and post-production. An overview of the Avid info is at a site called Reel Seo.
Excerpts from Quantel Digital Factbook
16:9 Picture aspect ratio used for HDTV and some SDTV(usually digital). See also: Widescreen
24P Refers to 24frames-per-second,progressive scan. This has been the frame rate of motion picture film since talkies arrived. It is also one of the rates allowed for transmission in the DVB and ATSC television standards – so they can handle film without needing any frame-rate change (3:2pull-down for60 fields-per-second systems or running film at25fps for50 Hz systems). It’s now accepted as a part of television production formats – usually associated with high definition 1080 lines, progressive scan. A major attraction is a relatively easy path from this to all major television formats as well as offering direct electronic support for motion picture film and D-cinema. See also: 24PsF,25P,3:2Pull-down,1080/24P– The Global Production Format? (Opinion),ATSC,Common Image Format,D-cinema,Digital Film Supplement,DVB, Publishing
25P Refers to 25 frames-per-second,progressive scan. Despite the international appeal of 24P,25Pis widely used for HD productions in Europe and other countries using 50 Hz TV systems. This is a direct follow-on from the practice of shooting film for television at 25fps. See also: 24P,24PsF,Common Image Format,DVB
Anamorphic Generally refers to the use of16:9aspectratio pictures in a 4:3 system. For example, anamorphic supplementary lenses are used to change the proportions of an image to 16:9on the surface of a 4:3 sensor by either extending the horizontal axis or compressing the vertical. Signals from 16:9cameras and telecines produce an ‘anamorphic’ signal which is electrically the same as with 4:3 images but will appear horizontally squashed if displayed at4:3. The alternative way of carrying 16:9pictures within 4:3 systems is letterbox. Letterbox has the advantage of showing the correct16:9 aspect ratio on 4:3 displays, however the vertical resolution is less than 16:9 anamorphic. See also: Aspect ratio – of pictures
Aspect ratio 1. – of pictures. The ratio of length to height of pictures. Nearly all TV screens are currently 4:3, i.e. four units across to three units in height but there is a growing move towards widescreen 16:9. Pictures presented this way are believed to absorb more of our attention and have obvious advantages in certain productions,such as sport. In the change towards 16:9 some in-between ratios have been used,such as 14:9. See also: Anamorphic, Widescreen, HDTV Website: documentR95-2000 athttp://www.ebu.ch/tech_texts.html 2. – of pixels. The aspect ratio of the area of a picture described by one pixel. The ITU-R BT.601digital coding standard defines luminance pixels which are not square. In the 525/60 format there are 486 active lines each with 720 samples of which 711 may be viewable due to blanking. Therefore the pixel aspect ratio on a 4:3 screen is: 486/711x 4/3 = 0.911 (i.e. the pixels are 10 percent taller than they are wide) For the 625/50 format there are 576 active lines each with 720 samples of which 702 are viewable so the pixel aspect ratio is: 576/702x 4/3 = 1.094 (i.e. the pixels are 9% wider than they are tall) A The newer DTV image standards, and all those for HD,define square pixels. Account must be taken of pixel aspect ratios – for example in executing a DVE move – when rotating a circle, the circle must always remain circular and not become elliptical. Another area where pixel aspect ratio is important is in the movement of images between computer platforms and television systems. Computers nearly always use square pixels so their aspect ratio must be adjusted to suit television. This change may not be real-time and its quality will depend on the processing used. See also: ARC, Pixel
ATSC The (US) Advanced Television Systems Committee. Established in 1982 to co-ordinate the development of voluntary national technical standards for the generation, distribution and reception of high definition television. In 1995 the ATSC published “The Digital Television Standard” which describes the US Advanced Television System. This uses MPEG-2 compression for the video and AC-3 for the audio and includes a wide range of video resolutions (as described in ATSC Table 3) and audio services (Table 2). It uses 8 and 16 VSB modulation respectively for terrestrial and cable transmission. See also: VSB,Table 2,Table 3,Dolby Digital (DD/AC-3),MPEG-2section Website: www.atsc.org
Compression (video) The process of reducing the bandwidth or data rate of a video stream. The analogue broadcast standards used today, PAL, NTSC and SECAM are, in fact, compression systems which reduce the data content of their original RGB sources. Digital compression systems analyze their picture sources to find and remove redundancy and less critical information both within and between picture frames. The techniques were primarily developed for digital data transmission but have been adopted as a means of reducing transmission bandwidths and storage requirements on disks and VTRs. A number of compression techniques are in regular use, these include ETSI,JPEG, Motion JPEG,DV,MPEG-1,MPEG-2and MPEG-4. Where different techniques are used in the same stream, problems can occur and picture quality can suffer more than if the same method is used throughout. The MPEG-2family of compression schemes, which was originally designed for program transmission, has been adapted for studio use in Betacam SX and IMX recorders. C While there is much debate, and new technologies continue to be developed, it remains true that the best compressed results are produced from the highest quality source pictures. Poor inputs do not compress well. Noise, which may be interpreted as important picture detail, is the enemy of compression. See also: Compression ratio, Concatenation, Digital Betacam,ETSI,JPEG,MPEG-2,MPEG-4
Compression ratio The ratio of the size of data in the non-compressed digital video signal to the compressed version. Modern compression techniques start with component television signals beta variety of sampling systems are used,4:2:2(‘Studio’MPEG-2),4:2:0 (MPEG-2),4:1:1 (DVCPRO),etc. The compression ratio should not be used as the only method to assess the quality of a compressed signal. For a given technique, greater compression can be expected to result in worse quality but different techniques give widely differing quality of results for the same compression ratio. The only sure method of judgement is to make a very close inspection of the resulting pictures – where appropriate, re-assessing their quality after onward video processing. See also: Concatenation,DV,ETSI,JPEG,MPEG
Cross conversion Changing video material from one HD format to another. For example, going from 720/60Pto 1080/50I is a cross conversion. Note that this involves both changing picture size and the vertical scan from 60 Hz progressive to 50 Hz interlaced. Similar techniques are used as for standards conversion but the HD picture size means the processing has to work five or six times faster. See also: Down-res,Standards conversion,Up-res
Down conversion Down conversion is down-resing that includes changing vertical refresh rates. For instance, moving from 1080/60I to 576/50I is a down-conversion. See also: Cross conversion,Publishing,Standards conversion,Up-res
Down-res Decreasing the size of video images to fit another format. Typically this reduces an HD format to an SD format and, as the input images represent oversampled versions of output, the final quality should be excellent– better than an SD-shot original. Moving from 1080/60I to 480/60I is down-resing. Technically the process involves: spatial interpolation to reduce size while retaining quality, colour correction to compensate for the difference in HD and SD colour standards and possibly re-framing to fit16:9HD onto 4:3 SD. Note that down-res does not include any change of frame rate. See also: Down conversion,Formatconversion,Publishing,Standards conversion,Up-res
DSS Digital Satellite Service. One of the terms used to describe DTV services distributed via satellite.
HDCam Assigned D11,this is a series of VTRs based on the Betacam principles for recording HD video on a tape format which uses the same style of cassette shell as Digital Betacam, although with a different tape formulation. The technology supports both 1080 and 1035 line standards. Various methods are believed to be used to reduce the video data including pre-filtering,DCT-based intra-frame compression and sampling at around 3:1:1. Together these are said to provide data reduction of between 7and 10:1. Four non-compressed audio channels sampled at48 kHz,20 bits per sample, are also supported. HDCam camcorders provide HD acquisition and recording in a compact ergonomic package. One model is specifically for1080/24Poperation and aimed at addressing some current film areas. See also: 24PsF,CineAlta,D11 Website www.sonybiz.net/cinealta
HD D5 A D5 VTR that is able to handle component high definition signals. Using around 5:1 compression the signals connect via an HD-SDI link. HD D5 can be multi-format, operating at both SD and HD TV standards. It can replay 525-line D5 as well as HD D5 cassettes. Formats include 480/60I,1080/24P,1080/60I,1080/50I,1035/59.94I and 720/60P. The recorder can also slew between 24and 25 Hz frame rates for PAL programme duplication from a 1080/24Pmaster. Cassette recording times vary according to format, the longest is 155 minutes for1080/24P. Website: www.panasonic-broadcast.com
HD-SDI Standardized in SMPTE292M,this is a high definition version of the SDI (Serial Digital Interface) used forSD television. The serial bit-stream runs at1.485 Gb/s to carry up to 10-bitY,Cr,Cb component video as well as audio and ancillary data. It extends the use of the coax cable and BNC connector‘plug-and-play’interface familiar to television operations for decades. The interface is also specified for fibre for distances up to 2km. See also: Dual link,HSDL,SDI
HDTV High Definition Television. A television format with higher definition than SDTV. While DTV at625 or525 lines is usually superior to PAL and NTSC, it is generally accepted that720- line and upward is HD. This also has a picture aspect ratio of16:9. While there are many picture formats proposed and several in use, there is increasing consensus that1080 x 1920/24Pis a practical standard for global exchange. Many are planning to produce on this format. See also: 24P,ATSC,Common Image Format,DVB,Table 3
I Inter-frame (compression) Compression which involves more than one frame. Inter-frame compression compares consecutive frames to remove common elements and arrive at ‘difference’ information. MPEG-2uses two types of inter-frame processed pictures – the ‘P’(predictive) and ‘B’ (bi-directional) frames. As ‘P’ and ‘B’ frames are not complete in themselves but relate to other adjacent frames, they cannot be edited independently. See also: Cutedit,MPEG-2
Interlace (scan) Method of scanning lines down a screen – as used in most of today’s television broadcasts. Each displayed picture comprises two interlaced fields: field two fills in between the lines of field one. One field displays odd lines, then the other shows even lines. For analogue systems, this is the reason for having odd numbers of lines in a TV frame e.g. 525 and 625,so that each of the two fields contain a half-line, causing the constant vertical scan to place the lines of one field between those of the other. The technique improves the portrayal of motion and reduces picture flicker without having to increase the picture rate, and therefore the bandwidth or data rate. Disadvantages are that it reduces vertical definition of moving images to about70% (see Interlace Factor) of the progressive scan definition and tends to cause some horizontal picture detail to ‘dither’. Forprocessing, such as in DVE picture size changes, movement between fields has to be detected if the higher-quality frame-based processing is used. There is continuing debate about the use of interlaced and progressive scans for DTV formats. See also: Interlace Factor, Interlace or Progressive (Opinion),Progressive
Intra-frame (compression) Compression that occurs within one frame. The compression process only removes redundant information from within the frame itself. No account is taken of other frames. JPEG and the ‘I’ frames ofMPEG-2are coded in this way and use DCT. In the MPEG-2 sequence only I-frames can be edited as they are the only independent frames. See also: DCT,I-frame only,JPEG,MPEG-2
MPEG-4 ISO/IEC 14496. Whereas MPEG-1and MPEG-2are only about efficient storage and transmission of video and audio,MPEG-4 adds interactive graphics applications (synthetic content) and Interactive multimedia (World Wide Web, distribution often adds access to content). First published in early 1999,ithas already grown to embrace a wide range of service types. It specifies low bitrates (5-64kb/s) for mobile and internet applications with frame rates up to 15 Hz,and images up to 352x 288 pixels. At the higher end it works up SD, HD resolutions and beyond and uses bitrates up to 10 Mb/s. The video coding is said to be three times more complex than MPEG-2butis already 15 percent more efficient and may rise to 50 percent. There is also more complexity for the decoders but it is hoped that Moore’s Law will take care of that. It also includes multimedia storage, access and communication as well as viewer interaction and 3D broadcasting. Aural and visual objects (AVOs) represent the content which may be natural – from cameras ormicrophones,orsynthetic – generated by computers. Their composition is described by the Binary Format for Scene description (BIFS) – scene construction information to form composite audiovisual scenes from the AVOs. Hence, a weather forecast could require relatively little data – a fixed background image with a numberofcloud,sun,etc.,symbols appearing and moving, audio objects to describe the action and a video ‘talking head’ all composed and choreographed as defined by the BIFS. Viewer interactivity is provided by the selection and movement of objects or the overall point of view – both visually and aurally. QuickTime 6 and RealPlayer8 already make use ofMPEG-4. DVB is showing interest in including it in future specifications but there is no sign of a large-scale decamp from the very well established MPEG-2. Website: www.cselt.it/mpeg
MPEG-4 ISO/IEC 14496. Whereas MPEG-1and MPEG-2are only about efficient storage and transmission of video and audio,MPEG-4adds interactive graphics applications (synthetic content) and Interactive multimedia (World Wide Web, distribution of and access to content). First published in early 1999,ithas already grown to embrace a wide range of service types. It specifies low bitrates (5-64kb/s) for mobile and internet applications with frame rates up to 15 Hz, and images up to 352x 288 pixels. At the higher end it works up SD, HD resolutions and beyond and uses bitrates up to 10 Mb/s. The video coding is said to be three times more complex than MPEG-2butis already 15 percent more efficient and may rise to 50 percent. There is also more complexity for the decoders but it is hoped that Moore’s Law will take care of that. It also includes multimedia storage, access and communication as well as viewer interaction and 3D broadcasting. Aural and visual objects (AVOs) represent the content which may be natural – from cameras ormicrophones,orsynthetic – generated by computers. Their composition is described by the Binary Format for Scene description (BIFS) – scene construction information to form composite audiovisual scenes from the AVOs. Hence, a weather forecast could require relatively little data – a fixed background image with a numberofcloud,sun,etc.,symbols appearing and moving, audio objects to describe the action and a video ‘talking head’ all composed and choreographed as defined by the BIFS. Viewer interactivity is provided by the selection and movement of objects or the overall point of view – both visually and aurally. QuickTime 6 and RealPlayer8 already make use ofMPEG-4. DVB is showing interest in including it in future specifications but there is no sign of a large-scale decamp from the very well established MPEG-2. Website: www.cselt.it/mpeg
NTSC (television standard) The colour television system used in the USA,Canada,Mexico,Japan and more, where NTSC M is the broadcast standard (M defining the 525/60 line and field format). It was defined by the NTSC in 1953. The bandwidth of the NTSC system is 4.2MHzforthe luminance signal and 1.3 and 0.4 MHz for the I and Q colour channels. Note that the NTSC term is often incorrectly used to describe the 525-line format even when it is in component or digital form. In both these cases, NTSC, which includes the colour coding system, is not used. See also: YIQ
PAL Phase Alternating Line. The colour coding system for television widely used in Europe and throughout the world, almost always with the 625 line/50 field system. It was derived from the NTSC system but by reversing the phase of the reference colour burst on alternate lines (Phase Alternating Line) is able to correct for hue shifts caused by phase errors in the transmission path. Bandwidth for the PAL-I system is typically 5.5 MHz luminance, and 1.3 MHz for each of the colour difference signals, U and V. Note that the PAL term is frequently used to describe any 625/50I analogue format– even if it is component, or in the 576/50I digital television system where PAL coding is not used.
Pixel (orPel) A shortened version of’ Picture cell’ or ‘Picture element’. The name given to one sample of picture information. Pixel can refer to an individual sample of R,G,B luminance or chrominance, or sometimes to a collection of such samples if they are co-sited and together produce one picture element. See also: Aspect ratio – ofpixels,Sub-pixel
Progressive (scan) Method of scanning lines down a screen where all the lines of a picture are displayed in one continuous vertical scan. There are no fields or half pictures as with interlace scans. It’s commonly used with computer displays and is now starting to be used for some DTV formats,e.g. – 1080/24P,720/60P. The ‘P’denotes progressive. A high picture refresh rate is required to give good movement portrayal, such as for fast action and camera pans, and to avoid a flickery display. For television applications using progressive scanning, this implies a high bandwidth or data rate and high scanning rates on CRT displays. The vertical definition is equal to around 70% of the number of lines (Kell Factor) and does not show the dither of detail associated with interlaced scans. See also: 24P,Interlace,Interlace Factor, Interlaced or Progressive (Opinion)
Resolution A measure of the finest detail that can be seen,or resolved,in a reproduced image. Whilst it is influenced by the number of pixels in the display (e.g. high definition 1920 x 1080,broadcastSDTV720 x 576 or720 x 487) note that the pixel numbers do not define the resolution but merely the resolution of that part of the equipment chain. The quality of lenses,display tubes, film processes, editsystems and film scanners, etc. in fact any element in the programme stream (from scene to screen),must be taken into accounting assessing overall system resolution. See also: ATSC,Concatenation,HDTV,Table 3
SD Shortform for SDTV.
SDTV Standard Definition Television. A digital television system in which the quality is approximately equivalent to that of analogue 525/60 or625/50 systems.
Serial Digital Interface (SDI) The standard digital television studio connection based on a 270 Mb/s transfer rate. This is a 10-bit,scrambled,polarity-independentinterface,with common scrambling for both componentITU-RBT.601and composite digital video and four groups each of four channels of embedded digital audio. Most new broadcast digital equipment includes SDI which greatly simplifies its installation and signal distribution. It uses the standard 75 ohm BNC connector and coax cable as is commonly used for analogue video, and can transmit the signal over200 meters (depending on cable type). See also: 4:2:2,Dual link, Embedded audio,HD-SDI
Standards conversion Changing the standard of existing television material that may involve two processes (four if going from and to analogue coded systems such as PAL and NTSC). The two main processes are format conversion to change the spatial (horizontal and vertical) sizes of the pictures and changing the vertical scan rate. For broadcast applications this needs to be completed retaining the maximum possible fidelity of the input content. The former process involves the relatively straightforward task of spatial interpolation – spreading the information from the original pictures over a different pixel structure. Note that the crude method of dropping or repeating lines/pixels will give very poor results and the detail of the interpolation process is important for best results. The second process is more complex as, changing the number of frames or fields per second means creating new ones or removing some – preferably without upsetting the movement in the pictures, so simply repeating or dropping fields or frames will not do. For this the movement within the pictures has to be analyzed so that in-between pictures can be synthesized. This is a very specialized area and there are highly developed techniques used on the best modern standards converters that do this very well. See also: Format(conversion)
Table 3 (ATSC) Table 3 of the ATSC DTV Standard, Annexe A, summarises the picture formats allowable for DTV transmission in the USA. Any one of these may be compressed and transmitted. An ATSC receiver must be able to display pictures from any of these formats.
ATSC Annexe A,Table 3 Picture formats Legend
Aspect Ratio: 1= square samples, 2= 4:3 display aspect ratio, 3 = 16:9 display aspect ratio
Frame Rate: 1= 23.976 Hz, 2= 24Hz, 4= 29.97Hz, 5 = 30 Hz, 7= 59.94,8 = 60Hz
Vertical Scan: 0 = interlaced scan 1= progressive scan
*Note that1088lines are actually coded in order to satisfy the MPEG-2requirementthat the coded vertical size be a multiple of16(progressive scan) or32(interlaced scan).
The wide range of formats in Table 3 caters for schemes familiar to television and computers and takes account of different resolutions, scanning techniques and refresh rates. Although each has its own application and purpose, some of the combinations are more familiar than others, for example: 480 x 704at29.97and 30 Hz frame rates, interlaced scan is very close to ITU-RBT.601 – although the 704pixels per line is not directly compatible with 601’s 720. Other familiar standards can be seen in the table. Forexample,480 x 640,square pixels,4:3 aspect ratio and progressive scan is the VGA computer standard. It’s included in the DTV specification to allow direct digital transmission of a signal to VGA displays. For each frame size, a range of alternative frame rates is available to provide compatibility with existing transmission systems and receivers. 29.97Hzis needed to keep step with NTSC simulcasts. This frame rate is not required once NTSC is no longer transmitted! 30 Hz is easier to use, and does not involve considerations such as drop- frame timecode. 24Hzprogressive (24P) offers compatibility with film material.
Up-res The process which increases the number of pixels used to represent an image by interpolating between existing pixels to create the same image on a larger format. There is no implied change of vertical scan rate. Despite its name, the process does not increase the resolution of the image. See also: Down-res, Format conversion
Widescreen A TV picture that has an aspect ratio wider than the ‘normal’4:3 – usually 16:9– while still using the normal 525/60 or625/50 orSD video. 16:9is also the aspect ratio used for HDTV. There is an intermediate scheme using 14:9which is found to be more acceptable for those still using 4:3 displays. Widescreen is used on some analogue transmissions as well as many digital transmissions. The mixture of4:3 and 16:9programming and screens has greatly complicated the issue of safe areas.
Avid has also come out with some good documents that's similar to the Quantel document. It includes a pretty good guide to different video formats--although it misses some new ones like Panasonic's AVC-Intra. It's much more digestible than Quantel's. Like the Quantel, very geeky--topics include sampling, compression, digital film, and post-production. An overview of the Avid info is at a site called Reel Seo.
Excerpts from Quantel Digital Factbook
16:9 Picture aspect ratio used for HDTV and some SDTV(usually digital). See also: Widescreen
24P Refers to 24frames-per-second,progressive scan. This has been the frame rate of motion picture film since talkies arrived. It is also one of the rates allowed for transmission in the DVB and ATSC television standards – so they can handle film without needing any frame-rate change (3:2pull-down for60 fields-per-second systems or running film at25fps for50 Hz systems). It’s now accepted as a part of television production formats – usually associated with high definition 1080 lines, progressive scan. A major attraction is a relatively easy path from this to all major television formats as well as offering direct electronic support for motion picture film and D-cinema. See also: 24PsF,25P,3:2Pull-down,1080/24P– The Global Production Format? (Opinion),ATSC,Common Image Format,D-cinema,Digital Film Supplement,DVB, Publishing
25P Refers to 25 frames-per-second,progressive scan. Despite the international appeal of 24P,25Pis widely used for HD productions in Europe and other countries using 50 Hz TV systems. This is a direct follow-on from the practice of shooting film for television at 25fps. See also: 24P,24PsF,Common Image Format,DVB
Anamorphic Generally refers to the use of16:9aspectratio pictures in a 4:3 system. For example, anamorphic supplementary lenses are used to change the proportions of an image to 16:9on the surface of a 4:3 sensor by either extending the horizontal axis or compressing the vertical. Signals from 16:9cameras and telecines produce an ‘anamorphic’ signal which is electrically the same as with 4:3 images but will appear horizontally squashed if displayed at4:3. The alternative way of carrying 16:9pictures within 4:3 systems is letterbox. Letterbox has the advantage of showing the correct16:9 aspect ratio on 4:3 displays, however the vertical resolution is less than 16:9 anamorphic. See also: Aspect ratio – of pictures
Aspect ratio 1. – of pictures. The ratio of length to height of pictures. Nearly all TV screens are currently 4:3, i.e. four units across to three units in height but there is a growing move towards widescreen 16:9. Pictures presented this way are believed to absorb more of our attention and have obvious advantages in certain productions,such as sport. In the change towards 16:9 some in-between ratios have been used,such as 14:9. See also: Anamorphic, Widescreen, HDTV Website: documentR95-2000 athttp://www.ebu.ch/tech_texts.html 2. – of pixels. The aspect ratio of the area of a picture described by one pixel. The ITU-R BT.601digital coding standard defines luminance pixels which are not square. In the 525/60 format there are 486 active lines each with 720 samples of which 711 may be viewable due to blanking. Therefore the pixel aspect ratio on a 4:3 screen is: 486/711x 4/3 = 0.911 (i.e. the pixels are 10 percent taller than they are wide) For the 625/50 format there are 576 active lines each with 720 samples of which 702 are viewable so the pixel aspect ratio is: 576/702x 4/3 = 1.094 (i.e. the pixels are 9% wider than they are tall) A The newer DTV image standards, and all those for HD,define square pixels. Account must be taken of pixel aspect ratios – for example in executing a DVE move – when rotating a circle, the circle must always remain circular and not become elliptical. Another area where pixel aspect ratio is important is in the movement of images between computer platforms and television systems. Computers nearly always use square pixels so their aspect ratio must be adjusted to suit television. This change may not be real-time and its quality will depend on the processing used. See also: ARC, Pixel
ATSC The (US) Advanced Television Systems Committee. Established in 1982 to co-ordinate the development of voluntary national technical standards for the generation, distribution and reception of high definition television. In 1995 the ATSC published “The Digital Television Standard” which describes the US Advanced Television System. This uses MPEG-2 compression for the video and AC-3 for the audio and includes a wide range of video resolutions (as described in ATSC Table 3) and audio services (Table 2). It uses 8 and 16 VSB modulation respectively for terrestrial and cable transmission. See also: VSB,Table 2,Table 3,Dolby Digital (DD/AC-3),MPEG-2section Website: www.atsc.org
Compression (video) The process of reducing the bandwidth or data rate of a video stream. The analogue broadcast standards used today, PAL, NTSC and SECAM are, in fact, compression systems which reduce the data content of their original RGB sources. Digital compression systems analyze their picture sources to find and remove redundancy and less critical information both within and between picture frames. The techniques were primarily developed for digital data transmission but have been adopted as a means of reducing transmission bandwidths and storage requirements on disks and VTRs. A number of compression techniques are in regular use, these include ETSI,JPEG, Motion JPEG,DV,MPEG-1,MPEG-2and MPEG-4. Where different techniques are used in the same stream, problems can occur and picture quality can suffer more than if the same method is used throughout. The MPEG-2family of compression schemes, which was originally designed for program transmission, has been adapted for studio use in Betacam SX and IMX recorders. C While there is much debate, and new technologies continue to be developed, it remains true that the best compressed results are produced from the highest quality source pictures. Poor inputs do not compress well. Noise, which may be interpreted as important picture detail, is the enemy of compression. See also: Compression ratio, Concatenation, Digital Betacam,ETSI,JPEG,MPEG-2,MPEG-4
Compression ratio The ratio of the size of data in the non-compressed digital video signal to the compressed version. Modern compression techniques start with component television signals beta variety of sampling systems are used,4:2:2(‘Studio’MPEG-2),4:2:0 (MPEG-2),4:1:1 (DVCPRO),etc. The compression ratio should not be used as the only method to assess the quality of a compressed signal. For a given technique, greater compression can be expected to result in worse quality but different techniques give widely differing quality of results for the same compression ratio. The only sure method of judgement is to make a very close inspection of the resulting pictures – where appropriate, re-assessing their quality after onward video processing. See also: Concatenation,DV,ETSI,JPEG,MPEG
Cross conversion Changing video material from one HD format to another. For example, going from 720/60Pto 1080/50I is a cross conversion. Note that this involves both changing picture size and the vertical scan from 60 Hz progressive to 50 Hz interlaced. Similar techniques are used as for standards conversion but the HD picture size means the processing has to work five or six times faster. See also: Down-res,Standards conversion,Up-res
Down conversion Down conversion is down-resing that includes changing vertical refresh rates. For instance, moving from 1080/60I to 576/50I is a down-conversion. See also: Cross conversion,Publishing,Standards conversion,Up-res
Down-res Decreasing the size of video images to fit another format. Typically this reduces an HD format to an SD format and, as the input images represent oversampled versions of output, the final quality should be excellent– better than an SD-shot original. Moving from 1080/60I to 480/60I is down-resing. Technically the process involves: spatial interpolation to reduce size while retaining quality, colour correction to compensate for the difference in HD and SD colour standards and possibly re-framing to fit16:9HD onto 4:3 SD. Note that down-res does not include any change of frame rate. See also: Down conversion,Formatconversion,Publishing,Standards conversion,Up-res
DSS Digital Satellite Service. One of the terms used to describe DTV services distributed via satellite.
HDCam Assigned D11,this is a series of VTRs based on the Betacam principles for recording HD video on a tape format which uses the same style of cassette shell as Digital Betacam, although with a different tape formulation. The technology supports both 1080 and 1035 line standards. Various methods are believed to be used to reduce the video data including pre-filtering,DCT-based intra-frame compression and sampling at around 3:1:1. Together these are said to provide data reduction of between 7and 10:1. Four non-compressed audio channels sampled at48 kHz,20 bits per sample, are also supported. HDCam camcorders provide HD acquisition and recording in a compact ergonomic package. One model is specifically for1080/24Poperation and aimed at addressing some current film areas. See also: 24PsF,CineAlta,D11 Website www.sonybiz.net/cinealta
HD D5 A D5 VTR that is able to handle component high definition signals. Using around 5:1 compression the signals connect via an HD-SDI link. HD D5 can be multi-format, operating at both SD and HD TV standards. It can replay 525-line D5 as well as HD D5 cassettes. Formats include 480/60I,1080/24P,1080/60I,1080/50I,1035/59.94I and 720/60P. The recorder can also slew between 24and 25 Hz frame rates for PAL programme duplication from a 1080/24Pmaster. Cassette recording times vary according to format, the longest is 155 minutes for1080/24P. Website: www.panasonic-broadcast.com
HD-SDI Standardized in SMPTE292M,this is a high definition version of the SDI (Serial Digital Interface) used forSD television. The serial bit-stream runs at1.485 Gb/s to carry up to 10-bitY,Cr,Cb component video as well as audio and ancillary data. It extends the use of the coax cable and BNC connector‘plug-and-play’interface familiar to television operations for decades. The interface is also specified for fibre for distances up to 2km. See also: Dual link,HSDL,SDI
HDTV High Definition Television. A television format with higher definition than SDTV. While DTV at625 or525 lines is usually superior to PAL and NTSC, it is generally accepted that720- line and upward is HD. This also has a picture aspect ratio of16:9. While there are many picture formats proposed and several in use, there is increasing consensus that1080 x 1920/24Pis a practical standard for global exchange. Many are planning to produce on this format. See also: 24P,ATSC,Common Image Format,DVB,Table 3
I Inter-frame (compression) Compression which involves more than one frame. Inter-frame compression compares consecutive frames to remove common elements and arrive at ‘difference’ information. MPEG-2uses two types of inter-frame processed pictures – the ‘P’(predictive) and ‘B’ (bi-directional) frames. As ‘P’ and ‘B’ frames are not complete in themselves but relate to other adjacent frames, they cannot be edited independently. See also: Cutedit,MPEG-2
Interlace (scan) Method of scanning lines down a screen – as used in most of today’s television broadcasts. Each displayed picture comprises two interlaced fields: field two fills in between the lines of field one. One field displays odd lines, then the other shows even lines. For analogue systems, this is the reason for having odd numbers of lines in a TV frame e.g. 525 and 625,so that each of the two fields contain a half-line, causing the constant vertical scan to place the lines of one field between those of the other. The technique improves the portrayal of motion and reduces picture flicker without having to increase the picture rate, and therefore the bandwidth or data rate. Disadvantages are that it reduces vertical definition of moving images to about70% (see Interlace Factor) of the progressive scan definition and tends to cause some horizontal picture detail to ‘dither’. Forprocessing, such as in DVE picture size changes, movement between fields has to be detected if the higher-quality frame-based processing is used. There is continuing debate about the use of interlaced and progressive scans for DTV formats. See also: Interlace Factor, Interlace or Progressive (Opinion),Progressive
Intra-frame (compression) Compression that occurs within one frame. The compression process only removes redundant information from within the frame itself. No account is taken of other frames. JPEG and the ‘I’ frames ofMPEG-2are coded in this way and use DCT. In the MPEG-2 sequence only I-frames can be edited as they are the only independent frames. See also: DCT,I-frame only,JPEG,MPEG-2
MPEG-4 ISO/IEC 14496. Whereas MPEG-1and MPEG-2are only about efficient storage and transmission of video and audio,MPEG-4 adds interactive graphics applications (synthetic content) and Interactive multimedia (World Wide Web, distribution often adds access to content). First published in early 1999,ithas already grown to embrace a wide range of service types. It specifies low bitrates (5-64kb/s) for mobile and internet applications with frame rates up to 15 Hz,and images up to 352x 288 pixels. At the higher end it works up SD, HD resolutions and beyond and uses bitrates up to 10 Mb/s. The video coding is said to be three times more complex than MPEG-2butis already 15 percent more efficient and may rise to 50 percent. There is also more complexity for the decoders but it is hoped that Moore’s Law will take care of that. It also includes multimedia storage, access and communication as well as viewer interaction and 3D broadcasting. Aural and visual objects (AVOs) represent the content which may be natural – from cameras ormicrophones,orsynthetic – generated by computers. Their composition is described by the Binary Format for Scene description (BIFS) – scene construction information to form composite audiovisual scenes from the AVOs. Hence, a weather forecast could require relatively little data – a fixed background image with a numberofcloud,sun,etc.,symbols appearing and moving, audio objects to describe the action and a video ‘talking head’ all composed and choreographed as defined by the BIFS. Viewer interactivity is provided by the selection and movement of objects or the overall point of view – both visually and aurally. QuickTime 6 and RealPlayer8 already make use ofMPEG-4. DVB is showing interest in including it in future specifications but there is no sign of a large-scale decamp from the very well established MPEG-2. Website: www.cselt.it/mpeg
MPEG-4 ISO/IEC 14496. Whereas MPEG-1and MPEG-2are only about efficient storage and transmission of video and audio,MPEG-4adds interactive graphics applications (synthetic content) and Interactive multimedia (World Wide Web, distribution of and access to content). First published in early 1999,ithas already grown to embrace a wide range of service types. It specifies low bitrates (5-64kb/s) for mobile and internet applications with frame rates up to 15 Hz, and images up to 352x 288 pixels. At the higher end it works up SD, HD resolutions and beyond and uses bitrates up to 10 Mb/s. The video coding is said to be three times more complex than MPEG-2butis already 15 percent more efficient and may rise to 50 percent. There is also more complexity for the decoders but it is hoped that Moore’s Law will take care of that. It also includes multimedia storage, access and communication as well as viewer interaction and 3D broadcasting. Aural and visual objects (AVOs) represent the content which may be natural – from cameras ormicrophones,orsynthetic – generated by computers. Their composition is described by the Binary Format for Scene description (BIFS) – scene construction information to form composite audiovisual scenes from the AVOs. Hence, a weather forecast could require relatively little data – a fixed background image with a numberofcloud,sun,etc.,symbols appearing and moving, audio objects to describe the action and a video ‘talking head’ all composed and choreographed as defined by the BIFS. Viewer interactivity is provided by the selection and movement of objects or the overall point of view – both visually and aurally. QuickTime 6 and RealPlayer8 already make use ofMPEG-4. DVB is showing interest in including it in future specifications but there is no sign of a large-scale decamp from the very well established MPEG-2. Website: www.cselt.it/mpeg
NTSC (television standard) The colour television system used in the USA,Canada,Mexico,Japan and more, where NTSC M is the broadcast standard (M defining the 525/60 line and field format). It was defined by the NTSC in 1953. The bandwidth of the NTSC system is 4.2MHzforthe luminance signal and 1.3 and 0.4 MHz for the I and Q colour channels. Note that the NTSC term is often incorrectly used to describe the 525-line format even when it is in component or digital form. In both these cases, NTSC, which includes the colour coding system, is not used. See also: YIQ
PAL Phase Alternating Line. The colour coding system for television widely used in Europe and throughout the world, almost always with the 625 line/50 field system. It was derived from the NTSC system but by reversing the phase of the reference colour burst on alternate lines (Phase Alternating Line) is able to correct for hue shifts caused by phase errors in the transmission path. Bandwidth for the PAL-I system is typically 5.5 MHz luminance, and 1.3 MHz for each of the colour difference signals, U and V. Note that the PAL term is frequently used to describe any 625/50I analogue format– even if it is component, or in the 576/50I digital television system where PAL coding is not used.
Pixel (orPel) A shortened version of’ Picture cell’ or ‘Picture element’. The name given to one sample of picture information. Pixel can refer to an individual sample of R,G,B luminance or chrominance, or sometimes to a collection of such samples if they are co-sited and together produce one picture element. See also: Aspect ratio – ofpixels,Sub-pixel
Progressive (scan) Method of scanning lines down a screen where all the lines of a picture are displayed in one continuous vertical scan. There are no fields or half pictures as with interlace scans. It’s commonly used with computer displays and is now starting to be used for some DTV formats,e.g. – 1080/24P,720/60P. The ‘P’denotes progressive. A high picture refresh rate is required to give good movement portrayal, such as for fast action and camera pans, and to avoid a flickery display. For television applications using progressive scanning, this implies a high bandwidth or data rate and high scanning rates on CRT displays. The vertical definition is equal to around 70% of the number of lines (Kell Factor) and does not show the dither of detail associated with interlaced scans. See also: 24P,Interlace,Interlace Factor, Interlaced or Progressive (Opinion)
Resolution A measure of the finest detail that can be seen,or resolved,in a reproduced image. Whilst it is influenced by the number of pixels in the display (e.g. high definition 1920 x 1080,broadcastSDTV720 x 576 or720 x 487) note that the pixel numbers do not define the resolution but merely the resolution of that part of the equipment chain. The quality of lenses,display tubes, film processes, editsystems and film scanners, etc. in fact any element in the programme stream (from scene to screen),must be taken into accounting assessing overall system resolution. See also: ATSC,Concatenation,HDTV,Table 3
SD Shortform for SDTV.
SDTV Standard Definition Television. A digital television system in which the quality is approximately equivalent to that of analogue 525/60 or625/50 systems.
Serial Digital Interface (SDI) The standard digital television studio connection based on a 270 Mb/s transfer rate. This is a 10-bit,scrambled,polarity-independentinterface,with common scrambling for both componentITU-RBT.601and composite digital video and four groups each of four channels of embedded digital audio. Most new broadcast digital equipment includes SDI which greatly simplifies its installation and signal distribution. It uses the standard 75 ohm BNC connector and coax cable as is commonly used for analogue video, and can transmit the signal over200 meters (depending on cable type). See also: 4:2:2,Dual link, Embedded audio,HD-SDI
Standards conversion Changing the standard of existing television material that may involve two processes (four if going from and to analogue coded systems such as PAL and NTSC). The two main processes are format conversion to change the spatial (horizontal and vertical) sizes of the pictures and changing the vertical scan rate. For broadcast applications this needs to be completed retaining the maximum possible fidelity of the input content. The former process involves the relatively straightforward task of spatial interpolation – spreading the information from the original pictures over a different pixel structure. Note that the crude method of dropping or repeating lines/pixels will give very poor results and the detail of the interpolation process is important for best results. The second process is more complex as, changing the number of frames or fields per second means creating new ones or removing some – preferably without upsetting the movement in the pictures, so simply repeating or dropping fields or frames will not do. For this the movement within the pictures has to be analyzed so that in-between pictures can be synthesized. This is a very specialized area and there are highly developed techniques used on the best modern standards converters that do this very well. See also: Format(conversion)
Table 3 (ATSC) Table 3 of the ATSC DTV Standard, Annexe A, summarises the picture formats allowable for DTV transmission in the USA. Any one of these may be compressed and transmitted. An ATSC receiver must be able to display pictures from any of these formats.
ATSC Annexe A,Table 3 Picture formats Legend
Aspect Ratio: 1= square samples, 2= 4:3 display aspect ratio, 3 = 16:9 display aspect ratio
Frame Rate: 1= 23.976 Hz, 2= 24Hz, 4= 29.97Hz, 5 = 30 Hz, 7= 59.94,8 = 60Hz
Vertical Scan: 0 = interlaced scan 1= progressive scan
*Note that1088lines are actually coded in order to satisfy the MPEG-2requirementthat the coded vertical size be a multiple of16(progressive scan) or32(interlaced scan).
The wide range of formats in Table 3 caters for schemes familiar to television and computers and takes account of different resolutions, scanning techniques and refresh rates. Although each has its own application and purpose, some of the combinations are more familiar than others, for example: 480 x 704at29.97and 30 Hz frame rates, interlaced scan is very close to ITU-RBT.601 – although the 704pixels per line is not directly compatible with 601’s 720. Other familiar standards can be seen in the table. Forexample,480 x 640,square pixels,4:3 aspect ratio and progressive scan is the VGA computer standard. It’s included in the DTV specification to allow direct digital transmission of a signal to VGA displays. For each frame size, a range of alternative frame rates is available to provide compatibility with existing transmission systems and receivers. 29.97Hzis needed to keep step with NTSC simulcasts. This frame rate is not required once NTSC is no longer transmitted! 30 Hz is easier to use, and does not involve considerations such as drop- frame timecode. 24Hzprogressive (24P) offers compatibility with film material.
Up-res The process which increases the number of pixels used to represent an image by interpolating between existing pixels to create the same image on a larger format. There is no implied change of vertical scan rate. Despite its name, the process does not increase the resolution of the image. See also: Down-res, Format conversion
Widescreen A TV picture that has an aspect ratio wider than the ‘normal’4:3 – usually 16:9– while still using the normal 525/60 or625/50 orSD video. 16:9is also the aspect ratio used for HDTV. There is an intermediate scheme using 14:9which is found to be more acceptable for those still using 4:3 displays. Widescreen is used on some analogue transmissions as well as many digital transmissions. The mixture of4:3 and 16:9programming and screens has greatly complicated the issue of safe areas.
Saturday, January 12, 2008
Apple Updates the Mac Pro
Apple has refreshed the Mac Pro--the first full turnover of the Mac Pro since it was first announced in August of 2006. The line has switched from being dominated by Quad-core Xeon's to being dominated by Octo-core Xeon's. There was an uptick in price for the recommended system from $2500 to $2800 for an 8-core 2.8 GHz Xeon Mac Pro.There are some other improvements in the system architecture and early results show good improvements in system performance. While adding 4 more cores doesn't double the speed, these systems look signficantly faster than older Mac Pro's, especiallly in encoding video. Check out this benchmark test from MacWorld for more info:
"From the Lab: Internal changes bolster latest Mac Pro"
I was surprised at what low marks they gave the internal hard drive that ships with the new Mac. I've always assumed that those had decent performance, but MacWorld found a significant speed bump on their multi-app test by putting a hard drive from an older Mac Pro into the current 8-core 2.8 GHz Xeon. For some good specs on hard drive performance, check out Bare Feats. Apple also has some performance comparisons with other Mac towers here, including rendering & encoding with FCP and After Effects.
There had been rumors that Apple was ready to add a Blu-ray drive for playing back high-def movies to the Mac Pro's. For PC's, adding an HD DVD or Blu-ray drive, or both, is now a common option. Nothing from Apple about Blu-ray for these new computers, but an announcement could come at the MacWorld Conference. I'm anxious to see Apple add Blu-ray disc authoring to DVD Studio Pro, as well as decent support for the HD DVD standard. Adobe's Encore already does this. Commentator Bob Cringely suggests that Jobs will ignore high-def discs because he sees them as a threat to iTunes ruling the media world in his latest column (he also thinks Apple will buy Adobe, which seems a bit far-fetched to me.)
Saturday, January 5, 2008
Upscaling Software Comparison
"Integrating DV Source Footage into HDV Projects, Part 2" by Jan OzerNeed to incorporate some standard-def footage into a high-def project? Then check out this article. It compares results of upscaling standard def footage to HD with 5 different packages, including FCP. The long and short of it is that it looks like spending $99 on Red Giant Software's Instant HD provides some nice improvements over the built-in scaling of FCP and Premiere Pro.
The article has some very handy comparison shots of the results from different packages. Click on the image with this post to see a larger view of a comparison of Instant HD and FCP. The image shows at the top, Instant HD, and below it, FCP. The handy red circles gives you points of comparison. Instant HD doesn't help with every shot though, and it doesn't create miracles, i.e., make your SD look as sharp as if it was actually shot in HD.
Not included in the comparison is a workflow mentioned by the author in another article that I posted about earlier--using Compressor. I think a good deinterlace from Compressor would have helped with some of the jaggies that showed up in all of the FCP examples of up-rezing. On the other hand, Compressor's good deinterlacing is very slow and the workflow is more complicated than just popping on a filter, like Instant HD, right in Final Cut.
The clear winner in the comparison, Algolith by AlgoSuite, is no longer available. The company has decided to discontinue the software to focus on dedicated hardware that does real-time processing. Not tested in this article is hardware-based upscaling like the AJA Kona 3 does or the Terranex.
Tuesday, December 11, 2007
Scaling Up your Video
Integrating DV Source Footage into HDV Projects, Part 1 By Jan Ozer
This is a good article on the basic issues on scaling up footage for high-definition video. Goes over frame resolution, pixel aspect ratio, and interlace. One good tidbit mentions an advantage to using Compressor with interlaced footage:
This article says that FCP and Compressor do an equivalent job of scaling-up video. But early this year I wrote about a tip for getting better-quality uprez with Photoshop. A tricky workflow, but if quality really matters then it's doable.
[via FreshDV]
This is a good article on the basic issues on scaling up footage for high-definition video. Goes over frame resolution, pixel aspect ratio, and interlace. One good tidbit mentions an advantage to using Compressor with interlaced footage:
On the other hand, when converting from interlaced DV to progressive HD, deinterlacing is a huge component of the quality equation, which could and perhaps should change your workflow, particularly for Final Cut Pro editors. That’s because Final Cut Pro deploys different deinterlacing algorithms than Compressor, which uses the glacial but ultra-high quality Optical Flow algorithm from Shake. If converting from interlaced source to progressive, you may produce noticeably better quality by scaling and particularly deinterlacing in Compressor. This means creating a separate sequence for your SD footage, rendering it out through Compressor, then re-importing the file back into Final Cut Pro. On the other hand, I found scaling quality relatively close between Final Cut Pro and Compressor, so if you don’t need to de-interlace, scaling in Final Cut Pro should work just fine.
This article says that FCP and Compressor do an equivalent job of scaling-up video. But early this year I wrote about a tip for getting better-quality uprez with Photoshop. A tricky workflow, but if quality really matters then it's doable.
[via FreshDV]
Thursday, November 1, 2007
Codecs and Editing
"When to stay in the native codec of the source, and when to convert to something else."
by Philip Hodgetts
Good article by Philip Hodgetts over at kenstone.net. A pretty thorough run-thru of recommendations of what codec to edit in based on what codec you shoot on. Also talks about how to convert to other codecs using the batch export command.
I wonder about his recommendation to convert HDV to ProRes 422 though. The article says to convert HDV to ProRes 422 either during capture if you'd got the hardware or by converting in FCP after capture. I would probably edit in the native codec, but render to ProRes 422. I've never been through the lengthy conforming that he describes HDV requires when you master back to HDV. Then again, I've never even posted in HD. But my thinking is that I'd rather save the storage by keeping footage in the more compressed HDV codec. (HDV is 25 mb/s while ProRes 422 for 1080 footage goes from 140 mb/s up to 220 mb/s.)
The article doesn't mention a workflow that we use at Link TV. Shoot on HDV, but use the deck to down-convert to DV. I think Sony's gear does a really good job on the down-conversion. I think it's better than what FCP does. I've captured some footage at HDV and then scaled it down in FCP to standard-def, and I don't think it looks as good as HDV down-converted in the deck. The article also covers the problems with DV in respect to color space.
[via StudioDaily Blog]
by Philip Hodgetts
Good article by Philip Hodgetts over at kenstone.net. A pretty thorough run-thru of recommendations of what codec to edit in based on what codec you shoot on. Also talks about how to convert to other codecs using the batch export command.
I wonder about his recommendation to convert HDV to ProRes 422 though. The article says to convert HDV to ProRes 422 either during capture if you'd got the hardware or by converting in FCP after capture. I would probably edit in the native codec, but render to ProRes 422. I've never been through the lengthy conforming that he describes HDV requires when you master back to HDV. Then again, I've never even posted in HD. But my thinking is that I'd rather save the storage by keeping footage in the more compressed HDV codec. (HDV is 25 mb/s while ProRes 422 for 1080 footage goes from 140 mb/s up to 220 mb/s.)
The article doesn't mention a workflow that we use at Link TV. Shoot on HDV, but use the deck to down-convert to DV. I think Sony's gear does a really good job on the down-conversion. I think it's better than what FCP does. I've captured some footage at HDV and then scaled it down in FCP to standard-def, and I don't think it looks as good as HDV down-converted in the deck. The article also covers the problems with DV in respect to color space.
[via StudioDaily Blog]
Tuesday, October 16, 2007
iFlop
Just to prove I'm not a shill for Apple, here are a couple of their recent disappointments.
Back at NAB, Apple announced that Final Cut Server would be available by the summer of 2007. I gave it a positive plug at the time. Well summer came and went with nary another peep from Apple about Final Cut Server. Recently, Apple added to the FCS webpage a release date of "early 2008". I'm guessing we won't see it again until NAB 2008. Apple isn't known for vaporware, but this is a prime example.
"iFlop"
While I don't agree with everything in this article from Forbes, the Apple TV has had a disappointing run. While expecting it to become the iPod of the television might have been pushing it, even Steve Jobs went on to call the Apple TV a mere "hobby". Here is one of my old plugs for Apple TV where I hoped it would become a great platform the video podcasts like our Mosaic.
For me one of the big problems is that the product is basically designed only for high-def TV's, but Apple doesn't really have any high-def content. My guess is that this isn't mainly Apple's fault. I blame the entertainment companies who I think are afraid that Apple will corner the video market like they have cornered the music download market. Universal in particular has been playing hardball with Apple on its NBC TV Shows and and is trying to organize some other record labels for a competing music service. Another big feature missing on Apple TV is movie rentals. Steve Jobs has said that people want to "own" their music (I agree), so is that his view on movies or the entertainment companies'?
Just look at the HD-DVD and Blu-ray fiasco to see an example that the entertainment companies, not to mention the consumer electronics manufacturers, just don't get it. Most of the movies studios are only supporting either HD-DVD or Blu-Ray, not both formats. So if you want to watch Universal or Paramont pictures, then buy a HD-DVD player, but if you want Sony, 20th Century Fox, or Disney movies, then get a Blu-ray player. Average consumers would never buy into this crazy scheme. Each company is trying to maximize their own company's advantage to the detriment of the consumer and thus the overall market for high-def movies. For music, it took an explosion of illegal downloads, to scare the record labels into all buying into Apple's music store. Here's one advocate for doing the same thing for video ("Apple TV Fails to Tap the Net's Limitless Library").
Not that Apple is blameless in the content world. Apple will not let other hardware manufacturers make products that will work with iTunes or play content with Apple's DRM for music or video. And Apple won't add support for content from other DRM schemes on their hardware. When it comes down to it, Apple is probably just as evil as Microsoft or the entertainment companies would be. But at least Apple's products are nearly all universally strong in interface, ease-of-use, quality, and reliability.
Back at NAB, Apple announced that Final Cut Server would be available by the summer of 2007. I gave it a positive plug at the time. Well summer came and went with nary another peep from Apple about Final Cut Server. Recently, Apple added to the FCS webpage a release date of "early 2008". I'm guessing we won't see it again until NAB 2008. Apple isn't known for vaporware, but this is a prime example.
"iFlop"
While I don't agree with everything in this article from Forbes, the Apple TV has had a disappointing run. While expecting it to become the iPod of the television might have been pushing it, even Steve Jobs went on to call the Apple TV a mere "hobby". Here is one of my old plugs for Apple TV where I hoped it would become a great platform the video podcasts like our Mosaic.
For me one of the big problems is that the product is basically designed only for high-def TV's, but Apple doesn't really have any high-def content. My guess is that this isn't mainly Apple's fault. I blame the entertainment companies who I think are afraid that Apple will corner the video market like they have cornered the music download market. Universal in particular has been playing hardball with Apple on its NBC TV Shows and and is trying to organize some other record labels for a competing music service. Another big feature missing on Apple TV is movie rentals. Steve Jobs has said that people want to "own" their music (I agree), so is that his view on movies or the entertainment companies'?
Just look at the HD-DVD and Blu-ray fiasco to see an example that the entertainment companies, not to mention the consumer electronics manufacturers, just don't get it. Most of the movies studios are only supporting either HD-DVD or Blu-Ray, not both formats. So if you want to watch Universal or Paramont pictures, then buy a HD-DVD player, but if you want Sony, 20th Century Fox, or Disney movies, then get a Blu-ray player. Average consumers would never buy into this crazy scheme. Each company is trying to maximize their own company's advantage to the detriment of the consumer and thus the overall market for high-def movies. For music, it took an explosion of illegal downloads, to scare the record labels into all buying into Apple's music store. Here's one advocate for doing the same thing for video ("Apple TV Fails to Tap the Net's Limitless Library").
Not that Apple is blameless in the content world. Apple will not let other hardware manufacturers make products that will work with iTunes or play content with Apple's DRM for music or video. And Apple won't add support for content from other DRM schemes on their hardware. When it comes down to it, Apple is probably just as evil as Microsoft or the entertainment companies would be. But at least Apple's products are nearly all universally strong in interface, ease-of-use, quality, and reliability.
Sunday, May 13, 2007
HD for Indies partners with Silverado Systems
"HD4NDs Big Announcement #2: Mike's Recommended System Configs via Silverado Systems "
I know this sounds like a press release, but I'm a big fan of Mike Curtis' HD for Indies website and I think he is on to something with this new venture. Silverado Systems, which is outside of Sacramento, CA is selling FCP systems that Mike recommends. Most of the systems are based on a write-up for DV.com that Mike did recently. I personally prefer to put together my own systems, but I have yet to tackle a system for high-def. And when trying something new, especially if it is as complex as putting together a system for uncompressed high-def editing, then it can't hurt to have a value-added reseller behind you if you can afford it.
I know this sounds like a press release, but I'm a big fan of Mike Curtis' HD for Indies website and I think he is on to something with this new venture. Silverado Systems, which is outside of Sacramento, CA is selling FCP systems that Mike recommends. Most of the systems are based on a write-up for DV.com that Mike did recently. I personally prefer to put together my own systems, but I have yet to tackle a system for high-def. And when trying something new, especially if it is as complex as putting together a system for uncompressed high-def editing, then it can't hurt to have a value-added reseller behind you if you can afford it.
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