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• Why does FFMPEG b-frames and b_pyramid offset start_pts (and start_time) in fragmented output ?

  13 juillet 2022, par Vans S

  It seems when transcoding something into fragmented or segmented output the start_pts is not 0, and no combination of options can make it 0 other than setting bframes to 0 and bpyramid to 0. This does not happen with regular nonfragmented output.

  


  Does anyone know why this is, and how to prevent it as I believe this is causing weird timesync issues with playback in browsers (every fragment slightly delays the video more and more) where after 2-3 hours the stream can end up 15minutes+ delayed.

  


  Example where each segment start_pts is not 0 :

  


  ffmpeg -i in.mp4 -pix_fmt yuv420p -an -f yuv4mpegpipe -frames:v 150 - | ffmpeg -f yuv4mpegpipe -i - -y -force_key_frames 1,2,3,4 -map 0 -codec:v libx264 -f segment -segment_list out.csv -segment_times 2,4 -segment_time_delta 0.05 -preset:v fast -segment_format_options movflags=+faststart out%03d.mp4


  


  start_pts is 0 here if we add :

  


  -x264opts b_pyramid=0 -bf 0 
#or change codec to
-codec:v mpeg4
#or output regular mp4
ffmpeg -i in.mp4 -pix_fmt yuv420p -an -f yuv4mpegpipe -frames:v 150 - | ffmpeg -f yuv4mpegpipe -i - -y out.mp4


  


  EDIT : Looking into this further I am starting to think this is a bug with how empty_moov interacts with the negative_cts_offsets flag. (when empty_moov is used, negative_cts_offsets seems to be ignored, and we need empty_moov for full webbrowser support.)

  


• Can ffmpeg extract multiple parts of a video file in a single command ?

  18 décembre 2020, par rcliao

  I have some huge MPEG files that is 24 hours long, and I need to extract a few parts (about 30 minutes each) of it into frame sequences (still images). I tried using commands like following :

  


  ffmpeg -i input.mpeg -ss 4:00:00 -to 4:30:00 outpath1\%05d.png
ffmpeg -i input.mpeg -ss 6:00:00 -to 6:30:00 outpath2\%05d.png
...


  


  But it seems that each time it is executed, ffmpeg scans the file from the beginning, causing the process to be very slow.

  


  For example, when I execute the above commands to extract the part of 4:00:00-4:30:00, ffmpeg will scan from 0:00:00 to 4:00:00, start extracting the image sequence, and stop at 4:30:00 ; and then I execute another command to extract the part of 6:00:00-6:30:00, and ffmpeg scans from 0:00:00 again to 6:00:00, and then start extracting.

  


  So I wanted to simplify this process to save time. Is there a way to extract multiple parts in a single command ? Like scans from 0:00:00 to 4:00:00, start extracting to 4:30:00, stop extracting and continue scanning to 6:00:00, and start extracting again...until the last part. Can ffmpeg do this ?

  


• Non-monotonous DTS after 26:30:02.81 recording time

  24 mars, par micha

  I record an hls stream and after 26:30:02.81 there come the message :

  



  [http @ 0x558330f5ba80] Opening 'http://de-origin-live-be-01.3qsdn.com:8081/3279/996191_PwxkbnqRThCDGXVr/l_94_95438333_16449.ts?nimblesessionid=2106' for reading
frame=2289669 fps= 24 q=-1.0 size=25056768kB time=26:30:02.81 bitrate=2151.6kbits/s speed=   1x    
[mpegts @ 0x558330f07280] Invalid timestamps stream=0, pts=10378, dts=8589926250, size=11200
[mpegts @ 0x558330f07280] Invalid timestamps stream=0, pts=2908, dts=8589929940, size=3407
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:0; previous: 8586744840, current: -3185972; changing to 8586744841. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598864, current: -1698561; changing to 4579598865. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598865, current: -1697537; changing to 4579598866. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598866, current: -1696513; changing to 4579598867. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:0; previous: 8586744841, current: -3182282; changing to 8586744842. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598867, current: -1695489; changing to 4579598868. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598868, current: -1694465; changing to 4579598869. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598869, current: -1693441; changing to 4579598870. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:0; previous: 8586744842, current: -3178502; changing to 8586744843. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:0; previous: 8586744843, current: -3174722; changing to 8586744844. This may result in incorrect timestamps in the output file.


  



  There is no more video written to the file at this time but ffmpeg is not stopping. If i stop it manual after 30 hours the file is only 26 hours 30 minutes long.

  



  How to reproduce :

  



  ffmpeg -progress recorder.progress -reconnect 1 -user_agent 'sdn/1.0' -i http://source/playlist.m3u8 -codec copy -bsf:a aac_adtstoasc record.mp4

ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
  configuration: --disable-debug --disable-doc --disable-ffplay --enable-shared --enable-avresample --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-gpl --enable-libass --enable-libfreetype --enable-libvidstab --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libxcb --enable-libx265 --enable-libxvid --enable-libx264 --enable-nonfree --enable-openssl --enable-libfdk_aac --enable-libkvazaar --enable-libaom --extra-libs=-lpthread --enable-postproc --enable-small --enable-version3 --enable-libbluray --enable-demuxer=dash --enable-decoder=hevc --enable-libxml2 --extra-cflags=-I/opt/ffmpeg/include --extra-ldflags=-L/opt/ffmpeg/lib --extra-libs=-ldl --prefix=/opt/ffmpeg
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100