AVI-Mux GUI - Definitions

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Definitions

Alexander Noé, April 11, 2006


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Definitions

chunk
A chunk is the smallest piece of data in an AVI file. A chunk can e.g. contain a video frame.
structure:
typedef struct {
DWORD dwFourCC;
DWORD dwLength;
BYTE bData[dwLength];
} CHUNK;
CRC check sum
A checksum that allows the detection (but not correction!) of errors in data read for example from a disc. A typical CRC checksum is a 32 bit value.
deltaframe
A frame which, unlike keyframes, only contains the differences to the previous frame. A deltaframe can only be decompressed if the previous frame has already been decompressed.
dropped frame
A frame that doesn't contain any data. When replaying a dropped frame, the previous frame is displayed again. This technique is used in AVI files to make one frame being displayed longer than another one, such as in 24fps/30fps hybrid files, which are stored at a framerate of 120 fps, with 3 or 4 dropped frames between 2 real frames.
dwDuration
The super index contains for every standard index it points to the amount of time it takes to replay all data that standard index points to. For Open-DML files created with VirtualDub up to 1.4.10 over 2 GB, the dwDuration values of the audio stream are corrupt.
frame header
MP3, AC3 and DTS streams contain some information about the frame (size, bitrate, samping rate etc) in the first bytes of each frame. AVI-Mux GUI doesn't support MP3-VBR / DTS streams with bad frame headers. Broken AC3 stream headers will not be copied either. If a broken AC3 stream header is encountered, the next valid one will be looked for. Any data between will be omitted.
Index
An index contains information about the position of video-, audio- or other index data. For AVI files, there are several types of indexes.
legacy index
This index is found in normal AVI files (called AVI 1.0 sometimes). It is always stored in one piece and points to video and audio data.
super index
The super index can only be found in Open-DML files. It is the upper level index of the hierarchic Open-DML AVI file index. It points to standard- or field index data. A super index shouldn't point to other super indexes
standard index
This one is also only found in Open-DML files. It is the lower level index of the hierarchic Open-DML AVI file index. It points to video- and audio data, using less space for one entry than the legacy index.
keyframe
A keyframe contains, unlike a deltaframe, a complete frame. In AVI terms, a keyframe can be seeked to very easily. In MPEG4-terms, it is not that easy: A B-frame succeeding such a keyframe could reference another frame preceding this keyframe. Then, the frame is still a keyframe, but not a so-called IDR-Frame. When storing MPEG4 in AVIs, reasonable encoders or muxers should only label IDR-frames as keyframes
Mode 2 Form 2
This is a possibility to store less error correction data to a CD and use the free space for own purposes. A sector can then contain 2324 bytes of user data instead of 2048. This is used for VCD and S-VCD for example. A "700 MB"-CD-R can then contain 798 MB without overburning. If you want to do this with AVI files, then please visit the homepage of Mode2CDMaker and read its readme-file carefully.
Open-DML
An extension to the AVI file format that allows the creation of AVI files larger than 2 GB. Open-DML files usually contain a hierarchic index structure with 2 levels (super- and standard indexes), and an additional legacy index is allowed. Read this to learn more or get the entire specification here.
Warning: Many hardware divX Players do not want to read Open-DML files!
rec-list
A special structure in an AVI file that contains lots of video and audio data. Such a structure is read in one piece by all players I know, so that larger blocks are read from the CD and less seek operations are necessary.
Warning: Some or all KISS players won't read files using rec lists. Disable rec lists if you intend to play your files on KISS players!