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• avformat/mux : Fix double-free when using AVPacket.opaque_ref

  1er septembre 2021, par Andreas Rheinhardt

  avformat/mux : Fix double-free when using AVPacket.opaque_ref
  Up until now, ff_write_chained() copied the packet (manually, not with
  
  av_packet_move_ref()) from a packet given to it to a stack packet whose
  
  timing and stream_index is then modified before being sent to another
  
  muxer via av_(interleaved_)write_frame(). Afterwards it is intended to
  
  sync the fields of the packet relevant to freeing again ; yet this only
  
  encompasses buf, side_data and side_data_elems and not the newly added
  
  opaque_ref. The other fields are not synced so that the returned packet
  
  can have a size > 0 and data != NULL despite its buf being NULL (this
  
  always happens in the interleaved codepath ; before commit
  
  fe251f77c80b0512ab8907902e1dbed3f4fe1aad it could also happen in the
  
  noninterleaved one). This leads to double-frees if the interleaved
  
  codepath is used and opaque_ref is set.
  This commit therefore changes this by directly reusing the packet
  
  instead of a spare packet. Given that av_write_frame() does not
  
  change the packet given to it, one only needs to restore the timing
  
  information to return it as it was ; for the interleaved codepath
  
  it is not possible to do likewise*, because av_interleaved_write_frame()
  
  takes ownership of the packets given to it and returns blank packets.
  
  But precisely because of this users of the interleaved codepath
  
  have no legitimate expectation that their packet will be returned
  
  unchanged. In line with av_interleaved_write_frame() ff_write_chained()
  
  therefore returns blank packets when using the interleaved codepath.
  Making the only user of said codepath compatible with this was trivial.
  * : Unless one wanted to create a full new reference.
  Reviewed-by : Lynne <dev@lynne.ee>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavformat/internal.h
  • [DH] libavformat/mux.c
  • [DH] libavformat/segment.c

• How to combine two .mka recording files to one stereo(dual channel) .wav file using FFMPEG

  21 mai 2019, par anoop v m

  I have two .mka recording files both have Date Time Original and Channel Layout : stereo in their metadata. I need to mix this two stereo type files to a single stereo file of type .wav. The timing should be preserved when overlaying. I am tired of getting this by using FFMPEG library. The resulting output is not stereo type and sometimes it is getting mixed up without considering the time of start. Please Help.
  Any help will be appreciated.

• Insert frames into video using FFMPEG

  29 octobre 2020, par Ryan Glanz

  The camera I am recording video with occasionally drops frames, so I need to reinsert frames into the video to keep the timing precise.

  



  I already have a script to identify exactly when those frames were dropped, so I have an index of every frame that needs to be inserted and where.

  



  For example, in a 100 s video at 100 FPS, I should have 10,000 frames. However, 4 frames were dropped at frame 399, 1205, 4299, and 7891. So, I want to either insert a black frame at the same resolution at those spots, or hold the previous frame for exactly one frame (e.g. hold frame 398 for an extra frame, or 0.01 s).

  



  Is there a way to do this iteratively in FFMPEG ? I am currently writing the video into its constituent frames, adding in my blank images, then re-concatenating the video from the frames, which is a very inefficient process.