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• ffmpeg, stretch audio to x seconds

  9 mai 2016, par Max Doumit

  I am trying to make an audio file be exactly x second.

  So far i tried using the atempo filter by doing the following calculation

  Audio length / desired length = atempo.

  But this is not accurate, and I am having to tweak the tempo manually to get it to an exact fit.

  Are there any other solutions to get this work ? Or am I doing this incorrectly ?

  My original file is a wav file, and my output in an mp3

  Here is a sample command

  ffmpeg -i input.wav -codec:a libmp3lame -filter:a "atempo=0.9992323" -b:a 320K output.mp3

  UPDATE.

  I was able to correctly calculate the tempo by changing the way I am receiving the audio length.

  I am now calculating the current audio length using the actual file size and the sample rate.

  Audio Length = file size / (sample rate * 2)

  Sample rate is something like 16000 Hz. You can get that by using ffprob or ffmpeg.

  EDIT - Solved

  Figured it out.
  I was calculating the tempo incorrectly.

  Audio length / desired length = atempo

  Should be

  desired length / Audio length = atempo

  I had to do a bit more reading on what the tempo actually does. Hope this helps someone.

• Moving files into sub folders based by average filesize

  5 février 2016, par darkshaed

  I need the help of you programming savants in creating a batch script or powershell script that will move and divide a group of files from one directory into 4 subdirectories based on an average total filesize. After the sort, the sub-directories should be roughly equal in terms of folder size.

  Why do I need this ?

  I have 4 computers that I would like to utilize for encoding via FFMPEG and it would be helpful for a script to divide a folder into 4 parts (sub-directories) based on a total average size.

  So lets say there are an assortment of movie files with varying different file sizes totaling to 100 GB, the script would divy the movie files and move them into 4 sub folders ; each folder having around 25 GB. Doing this will allow the 4 machines to encode the sum of the data equally and efficiently.

  After all that encoding I’ll have 2 files, XYZ.(original Extension) and XYZ.264, A script that could compare the 2 files and delete the larger file would be extremely helpful and cut down on manual inspection.

  Thank you, I hope this is possible.

• NReco ffmpeg library error

  19 janvier 2016, par agurodriguez

  I’m using NReco.VideoConverter for a video converting application. Now I’m trying to replace the audio in the source video for an mp3 track. I’m using this snippet from the official site : http://www.nrecosite.com/video_converter_net.aspx but I receiving this error :

  audio.mp3 : Invalid data found when processing input (exit code : 1)

  var ffmpeg = new NReco.VideoConverter.FFMpegConverter();
  
  ffmpeg.ConvertMedia("video.mp4", null, "output_video.mp4", null, new ConvertSettings() {
  
    AudioCodec = "copy", VideoCodec = "copy",
  
    CustomInputArgs = String.Format(" -i \"{0}\" ", "audio.mp3"),
  
    CustomOutputArgs = " -map 0 -map 1",
  
  });

  I tried with different audio files but still the same scenario.

  Hope you can help me !
  Regards