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• combine specific mpeg-dash segments (ex int.mp4 + seg_1.m4s +seg_3.m4s) into one single mp4 file

  16 avril 2019, par Liquid

  I am working one video transcoding in FFmpeg and MP4Box. Currently I am trying to combine/merge/concatenate specific MPEG-DASH video segments(m4s ex:int.mp4, seg_1.m4s, seg2,m4s,sge5.m4s) into one mp4 file.

  This the example of what I am trying to do.

  I have followed this thread ("Combine MPEG-DASH segments (ex, init.mp4 + segments.m4s) back to a full source.mp4 ?") but there is a problem while combining the specific m4s segments, while doing that it frames feazed in after seg2 and in seg5 it played again.

  Reference : FFmpeg example

• Timing breaks concatenating two identical videos after one has ATEMP/SETPTS altered

  25 mai 2019, par user3144514

  Video (B)
  Copy pasted and then doubled speed with Setpts and Atempo as Video (A)

  Concatenating them results in a video with the (A) portion playing at the expected 2x speed, but the (B) portion playing back at 1/2 speed.

  I am simply trying to speed up sections of video that are repetative and merge them back in.

  I have tried doing another round of SETPTS/ATEMPO with 1.0 values, but it doesn’t alter the outcome.

  I have also tried forcibly re-encoding A and B to ensure they match in formats, still no change.

  Speed Change

  ffmpeg -i source.mp4 -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" A.mp4

  Concatenation

  ffmpeg -i A.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts x1.ts
  
  ffmpeg -i B.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts x2.ts
  
  ffmpeg -i "concat:x1.ts|x2.ts" -c copy -bsf:a aac_adtstoasc C.mp4

  Do I need to use some other method to alter the playback rate without changing some internal timing value ?

  Or is there some way to fix the rates after adjusting SETPTS and ATEMPO so that the timing is restored ?

• avformat/matroskaenc : Rename functions to better reflect what they do

  15 avril 2020, par Andreas Rheinhardt

  avformat/matroskaenc : Rename functions to better reflect what they do
  EBML uses variable length integers both for the EBML IDs as well as for
  
  the EBML lengths ; Matroska also uses them for the TrackNumber in
  
  (Simple)Blocks and for the lengths of laces when EBML lacing is used.
  When encoding EBML lengths, certain encodings have a special meaning,
  
  namely that the element has an unknown length. This is not so when
  
  encoding general EBML variable length integers.
  Yet the functions called ebml_num_size() and put_ebml_num() had this
  
  special meaning hardcoded, i.e. they are there to write EBML lengths and
  
  not general EBML numbers. So rename them.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c