aviindex(1)
NAME
aviindex - Write and read text files describing the index of an AVI file
SYNOPSIS
aviindex [ -o ofile -i ifile -f -n -x -v -h ]
COPYRIGHT
aviindex is Copyright (C) 2003,2004 by Tilmann Bitterberg
DESCRIPTION
aviindex writes a text file describing the index of an AVI file. It
analyses the content or index if available of the AVI file and prints
this information in a human readable form.
An AVI file can have an optional chunk called "idx1" which contains
information about keyframes (syncpoints) and locations of video frames
resp. audio chunks. Though larger AVI files (>2-4GB), so-called OpenDML
AVI or also AVI 2 files, have a more complicated indexing system, which
consists of a superindex referring to (possibly) several "standard"
indexes, the "indexing principle" is the same. Movie players use such
indexes to seek in files.
aviindex reads the AVI file ifile and writes the index into ofile. This
can either happen in "dumb" mode where aviindex looks for an existing
index (and trusts this index!) in the file and dumps this index into a
human readable form. The "dumb" mode is used, when -n is NOT specified
or when the filesize of the input file is smaller than 2 GB.
In "smart" mode, aviindex scans through the complete AVI file and
searches for chunks (may that video or audio) and reconstructs the
index based on the information found. If an index chunk is found
accidently, aviindex will use the information in this index to recover
the keyframe information, which is important. aviindex will use smart
mode, if given the -n option OR if the AVI file is larger than 2 GB. If
the file is large, the index chunk cannot be found the usual way so one
must use -n but it is possible that there is an index chunk in this
file. Cross fingers.
Also in smart mode, aviindex analyzes the content of the video frame
and tries to detect keyframes by looking at the data depending on the
video codec.
The generated index file serves different purposes.
* The library which handles AVI files in transcode(1) can
read such index files and use this file to rebuild the
index instead of scanning through the whole AVI file over
and over again. Reading the index from the index file is
much faster than scanning through the AVI.
* It can be used as a seeking file. When given to transcode
via the --nav_seek switch, transcode will use the file to
seek directly to the position you specified via -c. This
also works for multiple -c ranges.
* Its nice to have for debugging.
OPTIONS
-o ofile
Specify the name of the output file.
-i ifile
Specify the name of the input file.
-f force the use of the existing index.
-n force generating the index by scanning the file.
-x (implies -n) don't use any existing index to generate keyframes.
-v show version.
-h show help text.
MPLAYER
aviindex can convert from and to mplayer-generated index files. Since
mplayer-1.0pre3 mplayer has the ability to save the index via -saveidx
FILE and load it again through -loadidx FILE. aviindex is able to
convert an mplayer index file to a transcode index file and vice visa.
It is not able to directly write an mplayer file, though. Example of a
toolchain
mplayer -frames 0 -saveidx mpidx broken.avi
aviindex -i mpidx -o tcindex
avimerge -x tcindex -i broken.avi -o fixed.avi
Or the other way round
aviindex -i broken.avi -n -o broken.idx
aviindex -i broken.idx -o mpidx
mplayer -loadidx mpidx broken.avi
The major differences between the two index file formats is that the
mplayer one is a binary format which is an exact copy of an index in
the AVI file. aviindex s format is text based. See FORMAT for
details.
EXAMPLES
The command
aviindex -i 3GBfile.avi -o 3GB.index
generates and index of the large file 3GBfile.avi. You can use the file
3GB.index to tell transcode to read the index from this file and not
from the avi. This leads to much faster startup time.
Suppose 3GBfile.avi has DivX video and PCM sound and you want to encode
several ranges.
transcode -V -i 3GBfile.avi --nav_seek 3GB.index \
-x xvid,avi \
-c 5000-6000,0:20:00-0:21:00,100000-100001 \
-y xvid --lame_preset standard -o out.avi
FORMAT
The format of the index file. The first 7 bytes in this file are
"AVIIDX1" for easy detection and a comment of who created the file.
The second line is a comment and describes the fields. Do not delete
it. Each line (except the first 2) consists of exactly 8 fields all
seperated by one space and describing one particular chunk of the AVI
file.
Here is an example of an AVI file with two audio tracks.
AVIIDX1 # Generated by aviindex (transcode-0.6.8)
TAG TYPE CHUNK CHUNK/TYPE POS LEN KEY MS
00db 1 0 0 2048 8335 1 0.00
01wb 2 1 0 10392 847 1 0.00
01wb 2 2 1 11248 847 1 0.00
02wb 3 3 0 12104 847 1 0.00
02wb 3 4 1 12960 847 1 0.00
00db 1 5 1 13816 5263 0 0.00
00db 1 6 2 19088 3435 0 0.00
01wb 2 7 2 22532 834 1 0.00
The field TAG is the chunk descriptor. Its "00d*" for the video, "01wb"
for the first audio track, "02wb" for the second audio track and so on.
The field TYPE is the type of the chunk. This is redundant because the
type is also embedded into the TAG field but its a convenient thing to
have. Its 1 for video, 2 for first audio track and 3 for second audio
track.
The field CHUNK is the absolute chunk number in the AVI file. If you
read the CHUNK field in the last line of the index file, you know how
many chunks this AVI file has.
The field CHUNK/TYPE holds information about how many chunks of this
type were previously found in the AVI file.
The field POS is the absolute byte position in the AVI file where this
chunk can be found. Note this field can hold really large numbers if
you are dealing with large AVIs.
The field LEN is the length of this chunk.
The field KEY holds information if this chunk is a keyframe. In the
example above, all audio chunks are key-chunks, but only the first
video frame is a key frame. This field is either 0 or 1.
The field MS holds information about how many milliseconds have passed.
This field may be 0.00 if unknown.
AUTHORS
aviindex was written by Tilmann Bitterberg <transcode at tibit.org> and is part of transcode.
SEE ALSO
avifix(1), avisync(1), avimerge(1), avisplit(1), tccat(1), tcdecode(1), tcdemux(1), tcextract(1), tcprobe(1), tcscan(1), transcode(1), mplayer(1)
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