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By Jim Armstrong
Production StategiesOne of the most important elements in producing QuickTime video movies is the quality of the original footage. The better the quality of the original video, the better the quality of the final QuickTime movie.
Making the ConnectionDo not overlook the connections between your equipment!
Tips for Improving the Frame RateDefragment your disk drive!A badly fragmented drive impacts performance.
Turn Off AppleTalk and Non-Essential ExtensionsTurning off AppleTalk improves performance. Turning off other non-essential screen extensions can also improve performance.
Set the Screen Depth to 16 Rather than 24 BitsIf your digitizing card supports both 16- and 24-bit screen depths, then digitize at 16 bits; particularly if you are using the Apple Video Compressor.A 16-bit image is 2/3 the size of a 24-bit image. The smaller sized image can be passed around much faster. The image quality of 16 versus 24 is very similar. The Apple Video Compressor only saves 16-bit information anyway. QuickTime relative performance in order of bit-depth, 1 being better performance:
Reduce the Frame Size The size of the frame affects the frame rate. Reducing the frame size increases the frame rate of the movie. When adjusting the frame size remember to check the frame size before recording. Note down the frame size and check it before you begin a recording session. It's very easy to adjust the frame size for one or two movies, then forget to adjust it for a second digitizing session.
Use the None CompressorCapturing using the None Compressor generally produces the highest frames rates (though if you have a fast processor, the Apple Video Compressor may be just as efficient). Capture using the None Compressor and then recompress using the Apple Video Compressor or the Compact Video Compressor. Several Applications, including VideoShop (Avid) and Movie Recorder (Apple) offer automatic post-compression options. These programs capture using the None Compressor, then immediately recompress using the compressor of your choice. We don't recommend using the Compact Video compressor in these situations.Note: This does NOT apply to recording using the VideoSpigot with the ScreenPlay application. ScreenPlay uses a special compressor which provides much higher frame rates. Also, if you are using the VideoSpigot, then use the application ScreenPlay to capture movies rather than recording in an application like Premiere or Movie Recorder. Much higher frame rates are possible using ScreenPlay. Use Faster EquipmentFaster Storage DeviceA faster hard disk usually improves your capture performance. QuickTime relative performance on storage devices, 1 being better performance:
Faster processorA faster processor improves your capture performance. QuickTime relative performance on processors, 1 being better performance:
Hardware compression boards (such as RasterOps MoviePak, SuperMacs Digital Film, and Radius VideoVision Studio) produce the highest frame rates possible. All three are capable of 30 frames per second, but they require fast processors (68040 or faster), fast hard disks (usually a disk array) and produce very large files which can take a long time to recompress.
Use Special Capture ApplicationsIt is possible to capture high frame rate movies without buying a new computer or hardware acceleration board. The utility Grab Guy (on the Apple QuickTime CD) performs multi-pass captures using a computer controllable Sony VCR (generally only the professional decks with time code support). Grab Guy captures every 6 frames (or so) and does multi-passes to record the whole movie.VideoToolKit from Abbate Video offers a step-record option. Using just about any controllable VCR, VideoToolKit places the VCR in pause, digitizes the frame, steps the VCR forward a frame, and digitizes the next frame. This requires a VCR with a clean pause, and places extra stress on the tape, but is a cheap alternative for capturing clips.
Determining the Optimum Frame RateIt's important to remember that the optimum frame rate is dependent not just on the capture hardware, but also on the playback platform. If you are recording for distribution on CD-ROM, Apple recommends the following:180x160 at 12 frames per second (compressed using Apple Video Compressor) 240x180 at 12 frames per second (compressed using the Compact Video Compressors) These numbers are designed to provide acceptable performance when playing on an LC from a standard speed CD-ROM. If the processor speed is larger, or a double-speed CD-ROM is assumed, then these figures increase.
Know Your Compression AlgorithmThe more you know about the compression algorithm you are using, the better you will know how to use it, and how to adjust the various parameters for best results. For example, reducing the luminance (brightness) information in an image will have a greater effect on compression performance than adjusting the chrominance (color). Most compression algorithms make use of the fact that the eye is less sensitive to changes in chrominance information than changes in luminance information. Many algorithms use color-subsampling to reduce the chrominance information. However, reducing the luminance information can reduce the data rate as well.Make sure the frame size is divisible by 4. The Compact Video Compressor is most efficient if the frame size (both horizontal and vertical) is evenly divisible by 4. That is, 240x180 is okay, but 242x182 is not as efficient.
Adjust Key FramesReducing the frequency of key frames will usually reduce the data rate, and improve performance, however reducing the key frame rate reduces performance when playing the movie in reverse, or when trying to skip ahead in a movie. Generally the Key Frame rate should be set to one per second of video, but if you know the movie will not be interrupted, searched or played in reverse, then you can increase this figure.
Use Filtered Down SamplingMost of the digitizing boards simply ignore or skip pixels to reduce the image size. For example, to create a 320x240 image, every second pixel is ignored. This results in stair stepping (aliasing) effects. To reduce these effects, capture the movie at a larger size, then recompress and resize the movie using filtered down sampling. ConvertToMovie and MovieShop both offer this option.
SoundCapture sound at 22 kHz. This provides the best quality. Downsample to 11 kHz for best quality and smallest size for distribution.To adjust the sound track, you can export the sound file from Premiere as an AIFF file and then use Sound Edit or another sound editing program to adjust the sound. Then bring the sound back into Premiere. The MacRecorder does not accurately stay at 22 kHz during recording. Use MovieShop to resample the sound during compression.
Creating QuickTime AnimationsPROMotion exports an animation to QuickTime. MovieWorks saves all of its animation in QuickTime format. MacroMind Director can save movies to QuickTime format, as well as play movies within an animation (you must have version 3.1 to do this. Also, if you are using hardware acceleration, get version 3.2 which fixes a problem in Director.)
3-D Programs Support QuickTimeMany 3-D programs now support QuickTime. Typestry from Pixer saves flying logos as a QuickTime movie. Infini-D can export a 3-D animation to QuickTime. It also lets you use a QuickTime movie as a surface within an animation (so you can have a QuickTime movie playing within a television set).
Playing Movies in HyperCardBoth Apple and Claris have released XCMDs for playing QuickTime movies in HyperCard. The Apple XCMDs are on the Apple QuickTime Developer CD, while the Claris XCMDs are available as part of HyperCard (and were available as an upgrade to owners of HyperCard). These XCMDs are different: the Apple XCMDs offer more sophisticated functions, but are not officially supported. You must license either set to distribute with your HyperCard stacks.
Use JPEG Compressor to Store MoviesMovie size can be reduced drastically by recompressing using the JPEG compressor. However, the movie does not play well when compressed using JPEG.
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This article provides tips for producing digitized video. There are a number of things you can do to improve capture performance and increase the frame rate of your movies. Some of these tips improve performance, and others only adjust performance marginally.
