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• why is FFMPEG framemd5 giving different audio sizes ?

  1er janvier 2019, par swami

  I am using FFmpeg framemd5 to verify that when I rewrap a Sony XDCAM "MP4" file to an MXF file I am not re-encoding the audio-video data. The "MP4" has a stereo file PCM audio stream, which has to be split into two mono streams for the MXF container. The video is 25 fps and the audio is 48000 sample rate. (I know that the MP4 container specification does not allow PCM as an audio stream. However, this is Sony’s special non-standard MP4 - which fortunately FFmpeg will still read)

  The first few lines of framemd5 output for my original (MP4) are as follows :

  0,          0,          0,        1,  3110400, 1851d2848eeef6636ea5ff1caa0c3555
  
  1,          0,          0,     1024,     4096, eb35a0242f1b59d64dc340913d4ba757
  
  1,       1024,       1024,     1024,     4096, 37c3a63ff6af92890056e42d8146275a

  The first few lines output for the MXF are as follows :

  0,          0,          0,        1,  3110400, 1851d2848eeef6636ea5ff1caa0c3555
  
  1,          0,          0,     1920,     3840, a01565b99da62249d86200070eff2729
  
  0,          1,          1,        1,  3110400, eb46f1690b2f8e3f32d07cf8ccefcdf4

  In the MXF output the "duration" for the audio stream is 1920 (which seems to make sense since 48000 / 25 = 1920, and the "size" is 3840 (which makes sense because 48000*16/8/25 = 3840)

  Can somebody explain why the MP4 file is having duration = 1024, and size = 4096

• ffmpeg : Concatenating videos with different codecs, sizes and formats [duplicate]

  10 juillet 2021, par Hitman47

  I am looking to concatenate a list of videos using ffmpeg that are of different sources, but the audio always goes out of sync and sometimes the playback speed goes wild.

  


  Even in the case of preconverting them separately to the same codec/size/frame rate, then trying to mux them together with codec copy, i get the same issues, so it must be something about mapping or timings.

  


  I am using the following parameters

  


  ffmpeg -f concat -safe 0 -i list.txt -map_metadata -1 -vf scale=480x270 -c:v libx265 -preset ultrafast -flags2 "fast" -vb 150k -max_interleave_delta 0 -r 22 -c:a opus -ab 30k -ac 1 -strict -2 -x265-params "--pmode --pme --ctu=32 --merange=20" output.mkv


  


  I have tried -max_interleave_delta 0 and disabling the experimental 'opus' codec and the nonstandard -flags2 "fast". The result is still broken

  


  These are the warnings i get in the output :
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x561090282280] Auto-inserting h264_mp4toannexb bitstream filter [concat @ 0x56108d88f400] DTS 1498384 < 4488000 out of order

  


  If this is very hard to pull off, would you suggest using something other than ffmpeg ?

  


• Can ffmpeg encode video from frames of different sizes ? [migrated]

  6 août 2013, par Camille Goudeseune

  I have a toolchain that produces frames that are usually 1920x1080, but occasionally 1919x1080 or 1920x1079. (Yes, this is a bug. Please read on.) When ffmpeg encodes a video from it, with a command like

  ffmpeg -y -r 30 -i foo/%04d.png -vcodec h264 out.mp4

  then it prints remarks like

  Input stream #0:0 frame changed from size:1919x1080 fmt:rgb24 to size:1920x1080 fmt:rgb24

  but those frames, rather than being resized and included in out.mp4, are omitted from out.mp4.

  Can those frames be included ? I found no mention of nonconstant frame size on forums and in documentation, but ffmpeg itself here claims to resize the frame. (The remark is printed at line 1688 of ffmpeg.c. There, a flag resample_changed is set, which causes the width and height fields of InputStream *ist to be corrected.)

  David Elliman may be reporting similar behavior in an answer to ffmpeg missing image frames in generated video from images .