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• FFmpeg concatenation changes the duration and playback speed of the input videos

  24 février 2017, par Barnaby

  I have two input videos that I am concatenating using the FFmpeg concat demuxer :

  ffmpeg -f concat safe '0' -i /path/to/file.txt -c copy /path/to/output.mp4

  The file.txt contains the two file paths as follows :

  ffconcat version 1.0
  
  
  
  file /path/to/input/file1.mp4
  
  
  
  file /path/to/input/file2.mp4

  Unfortunately, the concatenated video has two issues :

  • The duration of the first input video is 4 seconds. In the output video, the last frame freezes for several seconds before the second input video starts.
  • The playback speed of the second input video is slowed down so that instead of being 7 seconds long, the video plays for around 14 or 15 seconds.

  I have tried specifying the duration of each video in the .txt file, as specified by the FFmpeg docs, but this doesn’t seem to make a difference to the output.

  I’m a bit of a newbie to FFmpeg, so any help is greatly appreciated !

  Edit - The properties of each input video as given by FFprobe :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'tmp/video/16382802.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.25.100
  
    Duration: 00:00:04.43, start: 0.000000, bitrate: 644 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 360x640, 640 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
  
  
  
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'tmp/video/16382805.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.25.100
  
    Duration: 00:00:07.31, start: 0.023220, bitrate: 836 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 360x640, 669 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, 5.1, fltp, 158 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler

  Edit 2 - Stack trace when rewrapping the video (audio is lost) :

  ffmpeg version 3.0.1 Copyright (c) 2000-2016 the FFmpeg developers
  
    built with Apple LLVM version 7.3.0 (clang-703.0.31)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/3.0.1 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libxvid --enable-libfreetype --enable-ffplay --enable-libfdk-aac --enable-frei0r --enable-nonfree --enable-vda
  
    libavutil      55. 17.103 / 55. 17.103
  
    libavcodec     57. 24.102 / 57. 24.102
  
    libavformat    57. 25.100 / 57. 25.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 31.100 /  6. 31.100
  
    libavresample   3.  0.  0 /  3.  0.  0
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'https://s3-eu-west-1.amazonaws.com/stories.snaplytics.io/fTYbaN78DBVEQI0js0ydhNw/d3ef9a13-454c-4015-8412-cbd890e70e24.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.25.100
  
    Duration: 00:00:07.31, start: 0.023220, bitrate: 746 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 360x640, 669 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 67 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
  Input #1, lavfi, from 'anullsrc':
  
    Duration: N/A, start: 0.000000, bitrate: 705 kb/s
  
      Stream #1:0: Audio: pcm_u8, 44100 Hz, stereo, u8, 705 kb/s
  
  Output #0, mp4, to '/Users/barnabytaylor/Documents/fanbytes-dashboard/tmp/video/16382805.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.25.100
  
      Stream #0:0(und): Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 360x640, q=2-31, 669 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 30k tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1: Audio: aac (LC) ([64][0][0][0] / 0x0040), 44100 Hz, 5.1, fltp, 341 kb/s
  
      Metadata:
  
        encoder         : Lavc57.24.102 aac
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
    Stream #1:0 -> #0:1 (pcm_u8 (native) -> aac (native))
  
  Press [q] to stop, [?] for help
  
  frame=  219 fps= 57 q=-1.0 Lsize=   98706kB time=00:00:07.31 bitrate=110550.2kbits/s speed=1.91x    
  
  video:598kB audio:6kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 16257.420898%
  
  [aac @ 0x7ffbe2806e00] Qavg: 65536.000

• How to set audio speed to 0.3 in Ffmpeg ?

  15 septembre 2020, par WebDiva

  I am using ffmpeg to set the audio and video speed to 0.3x. I can set the video speed but can't set the audio speed to 0.3x. Here is the command

  


  ffmpeg -y -i video.mp4 -vf "setpts=PTS/0.3" -r 50 -c:v mpeg4 -b:v 1500k -af "atempo=0.3" output.mp4


  


  It says :

  


  Value 0.300000 for parameter 'tempo' out of range [0.5 - 100]


  


  Is there a workaround ? Any help will be appreciated. Regards.

  


• How can I speed up this side by side video stitch in FFMPEG

  21 octobre 2020, par ianf

  I have two videos the same size and pixel format (about 240x360) left and right that I want to stitch together.

  


  I'm using :

  


  ffmpeg -i left.mp4 -i right.mp4  -filter_complex "[0:v][1:v]hstack=inputs=2:shortest=1[v]; [0:a][1:a]amerge[a]" -map "[v]" -map "[a]" -ac 2 -shortest -y output.mp4


  


  which takes about 15 seconds on a 3 core machine. I see x1.25 on the conversion line.

  


  I know this isnt too bad, but any speed up I can make is going to help a lot as its in heavy use.

  


  Any ideas how I can improve this ?