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• How to extract frame types along with motion vectors using extract_mvs.c from ffmpeg

  26 février 2018, par helmo

  I have been researching ways to get frame types (I, P, B) along with the motion vector data returned from extract_mvs.c in the examples folder in ffmpeg.

  The extract_mvs.c file after it is compiled, returns information like this :

  framenum,source,blockw,blockh,srcx,srcy,dstx,dsty,flags
  
  2,-1,16,16,   8,   8,   8,   8,0x0
  
  2, 1,16,16,   8,   8,   8,   8,0x0
  
  2, 1,16,16,  24,   8,  24,   8,0x0
  
  2, 1,16,16,  40,   8,  40,   8,0x0
  
  2, 1,16,16,  56,   8,  56,   8,0x0
  
  2, 1,16,16,  72,   8,  72,   8,0x0
  
  2, 1,16,16,  88,   8,  88,   8,0x0
  
  ...
  
  297, 1,16,16, 248, 280, 248, 280,0x0
  
  297, 1,16,16, 264, 280, 264, 280,0x0
  
  297,-1,16,16, 278, 279, 280, 280,0x0
  
  297, 1,16,16, 280, 280, 280, 280,0x0
  
  297, 1,16,16, 296, 280, 296, 280,0x0
  
  297, 1,16,16, 312, 280, 312, 280,0x0
  
  297, 1,16,16, 328, 280, 328, 280,0x0
  
  297, 1,16,16, 344, 280, 344, 280,0x0

  Along with this information, I would like to output frame type so that I know framenum = 2 is, for example, a ’B’ frame.

  I tried different things, one of which was using a separate command :

  ffprobe input.mp4 -show_frames | grep -E 'pict_type|coded_picture_number'

  But the problem with this command is that it returns data like :

  pict_type=I
  
  coded_picture_number=0
  
  pict_type=B
  
  coded_picture_number=2
  
  pict_type=P
  
  coded_picture_number=1
  
  pict_type=B
  
  coded_picture_number=4
  
  pict_type=P
  
  coded_picture_number=3
  
  ....
  
  pict_type=P
  
  coded_picture_number=293
  
  pict_type=B
  
  coded_picture_number=297
  
  pict_type=B
  
  coded_picture_number=296

  And there is no much I can relate here between coded_picture_number and framenum. The former starts counting from 0 and the later from 2. I assume framenum starting from 2, means the count from this variable is actually from 1, and it ignored 1 in the extraction process as it is maybe an I frame thus no motion vectors.

  So, how can we use only extract_mvs.c to get not only that information it provides but also the frame types in the returned table. Any hints either syntax/command-wise or in editing the c file would be appreciated. Thanks in advance.

• avfilter/vf_paletteuse : Fix leaks of AVFilterFormats on error

  7 août 2020, par Andreas Rheinhardt

  avfilter/vf_paletteuse : Fix leaks of AVFilterFormats on error
  The paletteuse's query_formats function allocated three AVFilterFormats
  
  before storing them permanently. If allocating one of them failed, the
  
  three AVFilterFormats structures would be freed with av_freep() which
  
  does not free separately allocated subelements (namely the formats
  
  array) which leak.
  Furthermore, if storing one of the first two fails, the function simply
  
  returns and the ones not yet stored leak.
  These leaks have been fixed by only creating a new AVFilterFormats after
  
  the last one has already been permanently stored. Furthermore, it is
  
  enough to check whether the elements have been properly stored as
  
  ff_formats_ref() by design returns AVERROR(ENOMEM) if it is provided a
  
  NULL AVFilterFormats *.
  Fixes Coverity issues #1270818 and #1270819.
  Reviewed-by : Nicolas George <george@nsup.org>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavfilter/vf_paletteuse.c

• converting with the same quality

  26 mai 2019, par Sherkhan Azimov

  ffmpeg -i cam2.DAT -qscale:v cam2.avi
  When run, this returns "At least one output file must be specified", what am I missing ?
  Probably, there is another method to convert with the same quality ?