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• Audio decoders/encoders and different sample per frame rate

  24 juin 2021, par Salmond

  How to convert audio frame with different samples per frame rate to desired target rate using ffmpeg C libraries ? And what is the algorithm for that operation.

  


  I have a source MP3 file with 44100 sample rate and 1152 samples per frame. I want to encode it to AAC with the same sample rate but it expects 1024 samples per frame.

  


  As I understand, the algorithm for this operation would be to write 1024 samples from source, and then cache remaining 128 samples in a buffer, then on next packet read from this buffer and etc. Am I correct with that assumption or it is something completely different ?

  


• How can I use ffmpeg and PySceneDetect in pycharm to segment different scenes in a video

  13 mai 2020, par Runzhe

  I had a problem with a video that had multiple scenes.
Following the PySceneDetect tutorial, I know how to detect different scenes on the command line and split the video, such as "scenedetect - I goldeneye.mp4 -o output_dir detect-content -t 27 list-scenes save-images split-video".But I wanted to program a lot of these videos in Pycharm, because it would be slow if every video was on the command line. Therefore, I tried to find the corresponding operation in the SceneDetect Module, but I found that there was no relevant tutorial in the "Video Splitting" section, and the previous command line operation only mentioned that it could be used in this way directly. So how do I implement this in Pycharm ?

  


• In Command Line, how do I use a constant set by a nested For ?

  20 octobre 2016, par Neo Herakles

  Is it possible to set a variable through a For and then use its value ? I’m using two For, one to move across a whole folder and the other one to get the value I desire, the issue here is, the operation done by %watermark% doesn’t recognize the value of %duration%, I believe it’s trying the set the constant and then do the operation simultaneously and that’s why there’s no value, could you please tell me how to pass the variable’s value to duration ?

  @echo off
  
  setlocal
  
  for %%G in ("%~dp0\water\*.mp4") do (
  
      for /F "delims=" %%I in ('ffprobe.exe -v error -show_entries format^=duration -of default^=noprint_wrappers^=1:nokey^=1 %%I 2^>^&1') do (
  
      set "duration=%%I"
  
      ffmpeg.exe -i "%%G" -i Watermark.png -filter_complex "[0:v]scale=iw:ih[v0];[1:v][v0]scale2ref=iw/6:ih/10[logo][0v];[0v][logo]overlay=W-w-3:H-h-3:enable='between(t,%duration%/3,(%duration%/3)+2)'[v]" -map "[v]" -map 0:a -codec:v libx264 -preset ultrafast -crf 23 -codec:a copy "%~dp0\out\%%~nG.mp4"
  
      )
  
  )
  
  endlocal
  
  pause

  The output for this is Undefined constant or missing '(' in '/3)+2)so it’s definetely the constant the issue here.
  Thanks for the help.

  Edit : SOLVED, the solution was to use %%I instead of %duration%