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• iOS Recorded Video Playback on Android

  1er mars 2015, par Nirav

  I am trying to record video from iPhone device using UIImagePickerController and able to store it in MP4 format. The same video is uploaded on the Amazon S3 cloud.

  When I try to play the same video on Android devices, it fails to play with an error, cannot play.

  I searched forums/google and found that ffmpeg should be used to compress the video before uploading. I want to do the compression on the phone itself rather than on the server. Which is the best way to achieve this ?

  Regards,

  Nirav

• FFMpeg - Video conversion - .OGG to .MP4

  21 septembre 2018, par Hue Man

  After scouring the net, I can’t find anyone else trying to do this :
  Convert an OGG video format to MP4 video (usualy people are doing this the other way round).
  I have FFMpeg working just fine converting WEBM to MP4 but it just doesn’t seem to like OGG files.
  The official FFMpeg documentation says that it can both Encode AND Decode OGG files but for some reason it isn’t.
  Any ideas ?

• avfilter/formats : Fix heap-buffer overflow when merging channel layouts

  13 août 2020, par Andreas Rheinhardt

  avfilter/formats : Fix heap-buffer overflow when merging channel layouts
  The channel layouts accepted by ff_merge_channel_layouts() are of two
  
  types : Ordinary channel layouts and generic channel layouts. These are
  
  layouts that match all layouts with a certain number of channels.
  
  Therefore parsing these channel layouts is not done in one go ; instead
  
  first the intersection of the ordinary layouts of the first input
  
  list of channel layouts with the ordinary layouts of the second list is
  
  determined, then the intersection of the ordinary layouts of the first
  
  one and the generic layouts of the second one etc. In order to mark the
  
  ordinary channel layouts that have already been matched as used they are
  
  zeroed. The inner loop that does this is as follows :
  for (j = 0 ; j < b->nb_channel_layouts ; j++) 
  
      if (a->channel_layouts[i] == b->channel_layouts[j]) 
  
          ret->channel_layouts[ret_nb++] = a->channel_layouts[i] ;
  
          a->channel_layouts[i] = b->channel_layouts[j] = 0 ;
  
      
  
  
  (Here ret->channel_layouts is the array containing the intersection of
  
  the two input arrays.)
  Yet the problem with this code is that after a match has been found, the
  
  loop continues the search with the new value a->channel_layouts[i].
  
  The intention of zeroing these elements was to make sure that elements
  
  already paired at this stage are ignored later. And while they are indeed
  
  ignored when pairing ordinary and generic channel layouts later, it has
  
  the exact opposite effect when pairing ordinary channel layouts.
  To see this consider the channel layouts A B C D E and E D C B A. In the
  
  first round, A and A will be paired and added to ret->channel_layouts.
  
  In the second round, the input arrays are 0 B C D E and E D C B 0.
  
  At first B and B will be matched and zeroed, but after doing so matching
  
  continues, but this time it will search for 0, which will match with the
  
  last entry of the second array. ret->channel_layouts now contains A B 0.
  
  In the third round, C 0 0 will be added to ret->channel_layouts etc.
  
  This gives a quadratic amount of elements, yet the amount of elements
  
  allocated for said array is only the sum of the sizes of a and b.
  This issue can e.g. be reproduced by
  
  ffmpeg -f lavfi -i anullsrc=cl=7.1 \
  
   af 'aformat=cl=mono|stereo|2.1|3.0|4.0,aformat=cl=4.0|3.0|2.1|stereo|mono' \
  
   f null -
  The fix is easy : break out of the inner loop after having found a match.
  Reviewed-by : Nicolas George <george@nsup.org>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavfilter/formats.c