[FFmpeg-devel] [PATCH] avformat/riff: remove useless tag correlation 'mpg2'->MPEG1VIDEO.

Александр Слободенюк alexander.slobodeniuk at bramtech.ru
Tue Aug 1 14:50:27 EEST 2017

 This is actually a bug, that just doesn't affect anything.
 First  of all, the logic of functions that work with ff_codec_bmp_tags
 is "One tag -- one codec id", or "one codec id for one tag".
 Also  if  you  write  this tag as MPEG2VIDEO, and then read the header
 (all by ffmpeg), it will interpret as MPEG1VIDEO:
 ffmpeg -i whatever -vcodec mpeg2video test.avi
 && gdb ffprobe_g
(gdb) break avi_read_header
(gdb) r -i test.avi
(gdb) finish
(gdb) p s->>streams[0]->codecpar->codec_id

 if  you  will  write an mpeg1video , it will be created with tag
'mpg1',    not    'mpg2'    in    all   cases   (because   correlation
AV_CODEC_ID_MPEG1_VIDEO   --  'mpg1')  stands  before  'mpg2'  tag  in

ffmpeg -i whatever -vcodec mpeg1video test.avi
    Stream #0:0: Video: mpeg1video (mpg1 / 0x3167706D),
So, this patch does not affect on writing mpeg1video to riff files.
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