[FFmpeg-devel] MPEG index entries

[Taylan O. Toygarlar]

Hi Everyone,

I am trying to get MPEG frame accuracy through the internal index 
created within libavformat. I've seen that the index is updated during 
parsing, inside mpegps_read_pes_header. Is there any reason why it is 
not creating the indexes correctly? After my first decode, I have 13 
index entries, all initiated from inside mpegps_read_pes_header, through 
av_add_index_entry.

Second note, I would expect the keyframes to be collected, but there is 
no check for a keyframe, as it's commented when calling the function /* 
FIXME keyframe? */. Is there any magical way that makes this check 
inherent, but which I cannot see? I have my doubts, as with a movie of 9 
frame GOP structure, I have 50 index entries @ frame 400.

Has anyone before dealt with the MPEG indexes? Is this behaviour 
intentional, or should it be considered a bug? If not, how are the index 
entries used for MPEG seeking? If indexed entries are not keyframes, 
jumping to that location will have artifacts, isn't it true?

Thank you very much for your comments and input.

All the best,

-- 
Taylan Ozgur Toygarlar
Scientific Programmer, B.Sc.
Intelligent Systems Lab Amsterdam
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Faculty of Science - Informatics Institute
University of Amsterdam
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Amsterdam, The Netherlands

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