[FFmpeg-devel] Interpretation of duration field in AVI super index chunk
t.rapp at noa-audio.com
Tue Feb 24 16:33:10 CET 2015
I am currently trying to interpret the index data of HuffYuv/PCM AVI
files written by FFmpeg. If the file is larger than 2GiB an "AVIX" RIFF
chunk is added for each 2GiB-block, each of these blocks gets an OpenDML
chunk index "ix00" and an OpenDML super index chunk "indx" is written
for each stream that contains the file offset of the according chunk
indexes together with its size and total duration.
For this super index "duration" entry the documentation I have found
states that it shall be the "time span in stream ticks" . FFmpeg
seems to write the chunk count instead which is correct for video
streams where one data chunk "00dc" corresponds to one frame. For audio
streams one data chunk "01wb" usually contains multiple samples.
I guess for audio streams the "duration" should be multiplied by the
samples-per-chunk factor in avienc.c to allow third-party applications
to jump to the correct AVIX RIFF segment based on a given timestamp.
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