[Libav-user] Retrieval of side data from matroska file

Bartelme, John john.bartelme at lmco.com
Fri Nov 6 00:12:54 CET 2015

>From: Bartelme, John (US) 
>Sent: Thursday, November 05, 2015 11:13 AM
>To: 'libav-user at ffmpeg.org'
>Subject: Retrieval of side data from matroska file
>       I'm using version 2.7.2 and I'm trying to retrieve block additional side data from a matroska file.  Whenever I do an av_read_frame the side data is missing in the resulting packet.  Debugging matroskadec.c I can see that the side data is being read into >the internal packet but it looks like this data is lost when it is copied over in matroska_deliver_packet as that only memcpy's the AVPacket structure.  Is there a different way I should be doing this to get access to the side data in my file?  I'm also >concerned there may be a memory leak when an mkv file contains side data as the internal queue packets are only freed with av_freep in matroska_deliver_packet vs using av_free_packet like is used in matroska_clear_queue, but I may be missing >something.
>Thanks, John Bartelme

I've determined that this all gets done up in libavformat/utils.c and I need to add AVFMT_FLAG_KEEP_SIDE_DATA to my context.  Sorry to have wasted your time.  Thanks, John Bartelme

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