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• FFMPEG Slow Video and Audio by Half

  12 septembre 2021, par nomaam

  I am using the latest version of FFMPEG and am trying to slow video and audio by half

  


  This is the best I could come up with

  


  ./ffmpeg.exe -i "C:/ffmpeg/input.mp4" -filter_complex "[0:v]setpts=1.5*PTS[v];[0:a]atempo=0.5[a]" -map "[v]" -map "[a]" "C://ffmpeg/output.mp4"


  


  But the audio and video are not being slowed down at the same rate.

  


  Any suggestions ?

  


  Thanks.

  


• Cut every .mp4 in folder by half with ffmpeg

  14 novembre 2022, par c00kieRaptor

  I have a folder with 200 mp4-files and I need to cut the last half of every one of them. So if a video is 140 seconds I need to cut out the last 70 seconds so that the resulting output is the preceding 70 seconds.

  


  I would assume the loop would look a bit like this :

  


  for i in *.mp4; do
    let A=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 $i)
    let A=${A%.*}
    let A=$A/2
    ffmpeg -sseof $A -i $i ${i%.mp4}
done


  


  But I get "syntax error : invalid arithmetic operator (error token is ".246848")" from the first 'let'. This corresponds to the float of the video duration.
For all I know there could be many other mistakes with my loop

  


  Also some files have spaces and special characters if that matters.

  


• ffmpef cannot open a simple microsoft wav file exported with Audacity

  23 juillet 2013, par sebpiq

  I have exported a sound file to microsoft wav using Audacity.
  I am trying to open this file with ffmpeg :

  ffmpeg -i steps-stereo-16b-44khz.wav /tmp/test.ogg

  and here's the ouput I get :

  fmpeg version 1.2.1 Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Jun 12 2013 13:46:11 with Apple clang version 4.1 (tags/Apple/clang-421.11.66) (based on LLVM 3.1svn)
  
    configuration: --prefix=/opt/local --enable-swscale --enable-avfilter --enable-libmp3lame --enable-libvorbis --enable-libopus --enable-libtheora --enable-libschroedinger --enable-libopenjpeg --enable-libmodplug --enable-libvpx --enable-libspeex --enable-libass --enable-libbluray --enable-gnutls --enable-libfreetype --mandir=/opt/local/share/man --enable-shared --enable-pthreads --cc=/usr/bin/clang --arch=x86_64 --enable-yasm --enable-gpl --enable-postproc --enable-libx264 --enable-libxvid
  
    libavutil      52. 18.100 / 52. 18.100
  
    libavcodec     54. 92.100 / 54. 92.100
  
    libavformat    54. 63.104 / 54. 63.104
  
    libavdevice    54.  3.103 / 54.  3.103
  
    libavfilter     3. 42.103 /  3. 42.103
  
    libswscale      2.  2.100 /  2.  2.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  2.100 / 52.  2.100
  
  [dca @ 0x7fd30c013600] Not a valid DCA frame
  
  
  
  ... SNIP ...
  
  
  
  [dca @ 0x7fd5bc013600] Invalid bit allocation index
  
  [dca @ 0x7fd5bc013600] error decoding block
  
      Last message repeated 3 times
  
  [dca @ 0x7fd5bc013600] Didn't get subframe DSYNC
  
  [dca @ 0x7fd5bc013600] error decoding block
  
  [wav @ 0x7fd5bc013000] max_analyze_duration 5000000 reached at 5009070 microseconds
  
  [wav @ 0x7fd5bc013000] decoding for stream 0 failed
  
  [wav @ 0x7fd5bc013000] Could not find codec parameters for stream 0 (Audio: dts ([1][0][0][0] / 0x0001), 192000 Hz, 2 channels, fltp, 0 kb/s): no decodable DTS frames
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  steps-stereo-16b-44khz.wav: could not find codec parameters

  If I export the same file to .ogg or .aiff, no problem, the following works fine :

  ffmpeg -i steps-stereo-16b-44khz.aiff /tmp/test.ogg

  Any idea what could be wrong ?

  A link to my wav file so you can try to reproduce.

  NB my final goal is to slice the audio file. I know I can export file directly to .ogg with audacity. This is just a test case.