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• Cutting and rejoining videos causes audio de-synchronization using ffmpeg [closed]

  10 décembre 2023, par Donotalo

  This is the original post. I'm not getting any answer there so I thought may be the programming community knows the answer.

  


  Main Post

  


  I'm trying to cut a video into pieces and rejoin them using ffmpeg on Windows 11 x64. Here's the details of ffmpeg :

  


  ffmpeg version 2023-11-22-git-0008e1c5d5-full_build-www.gyan.dev Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --pkg-config=pkgconf --disable-w32threads
--disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp
--enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt
--enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2
--enable-libaribb24 --enable-libaribcaption --enable-libdav1d --enable-libdavs2 --enable-libuavs3d
--enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265
--enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx
--enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi
--enable-libharfbuzz --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg
--enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc
--enable-dxva2 --enable-d3d11va --enable-libvpl --enable-libshaderc --enable-vulkan --enable-libplacebo
--enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt
--enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame
--enable-libvo-amrwbenc --enable-libcodec2 --enable-libilbc --enable-libgsm --enable-libopencore-amrnb
--enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite
--enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil      58. 32.100 / 58. 32.100
  libavcodec     60. 34.100 / 60. 34.100
  libavformat    60. 17.100 / 60. 17.100
  libavdevice    60.  4.100 / 60.  4.100
  libavfilter     9. 13.100 /  9. 13.100
  libswscale      7.  6.100 /  7.  6.100
  libswresample   4. 13.100 /  4. 13.100
  libpostproc    57.  4.100 / 57.  4.100


  


  I've a video file in MKV format. I've cut it into 3 pieces using the following command :

  


  ffmpeg.exe -ss 0:0:0 -i input.mkv -t 0:54:15 -c:v hevc_amf -b:v 3M -c:s mov_text seg-01.mp4
ffmpeg.exe -ss 0:54:29 -i input.mkv -t 0:35:35 -c:v hevc_amf -b:v 3M -c:s mov_text seg-02.mp4
ffmpeg.exe -ss 1:30:12 -i input.mkv -t 0:4:10 -c:v hevc_amf -b:v 3M -c:s mov_text seg-03.mp4


  


  The audio is copied in all 3 pieces like original. Now I'm joining them using the following command :

  


  ffmpeg.exe -y -f concat -safe 0 -i .\join.txt -c:v hevc_amf -c:a copy -c:s copy -fflags +genpts out.mp4


  


  where, join.txt is :

  


  file seg-01.mp4
file seg-02.mp4
file seg-03.mp4


  


  ffmpeg throws the following warning :

  


  [mp4 @ 000002a5cf9cc040] Non-monotonic DTS in output stream 0:1; previous: 156240896, current: 156240084; changing to 156240897.
This may result in incorrect timestamps in the output file.
[mp4 @ 000002a5cf9cc040] Non-monotonic DTS in output stream 0:1; previous: 258720980, current: 258720462; changing to 258720981.
This may result in incorrect timestamps in the output file.


  


  I've observed that audio is de-synchronized after the places where I cut.

  


  How to keep audio, video and subtitle synchronized after cutting and rejoining the video using ffmpeg ?

  


• change audio part from mkv video file to flac audio file without losing quality [closed]

  29 août 2023, par Jimmy wu

  how could I write a Linux command to manipulate ffmpeg to change audio part from mkv video file to flac audio file without losing quality ?

  


  I use following command and I found that the size of audio file is almost the same as video file.

  


  ffmpeg -i "2023-08-28 15-32-02.mkv" -ss 0:0:0 -to 1:9:2

8 -vn -c:a flac 2023_08_28_CPU_DV_1.flac


  


  what command should I use ?

  


  I want to change "only audio part" from mkv video file to flac audio file without losing quality,

  


  then the size of file would not be that big

  


• How to put the output of ffmpeg into a pipe in Python ? [duplicate]

  16 février 2023, par Eric Palmer

  I'm trying to use python to feed the results of ffmpeg into a pipeline, and then I can use this pipeline for subsequent operations (such as rtmp streaming). I've written the correct command, but I don't know how to accomplish this with Python.

  


  I wrote the following code in the Shell, it can run correctly.

  


  ffmpeg -re -i '2023-02-16_21:02:50.mp4' -f mpegts -c:v copy -c:a aac -vbsf h264_mp4toannexb pipe:1.ts | cat >> push


  


  When I'm trying to do the above in Python, I'm getting an error.

  


  cat: '>>': No such file or directory


  


  Here is my python code.

  


  command = [
    'docker',
    'run',
    '-v',
    f'{cwd}:{cwd}',
    '-w',
    f'{cwd}',
    'jrottenberg/ffmpeg',
    '-re',
    '-i', f'{video_path}',
    '-f', 'mpegts',
    '-c:v', 'copy',
    '-c:a', 'aac',
    '-vbsf', 'h264_mp4toannexb',
    'pipe:1.ts',
]

pa = subprocess.Popen(
    command,
    stdout = subprocess.PIPE,
    stderr = error_file
)

command = [
    'cat',
    '>>',
    f'{pipe_name}'
]

with pa.stdout:
    pb = subprocess.Popen(
        command,
        stdin = pa.stdout,
        stdout = error_file,
        stderr = error_file
    )