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• FFMPEG Formating all videos in a folder to be the same for concating

  20 mars 2018, par borobosis

  Ok so I’m trying to make a programm that takes the mp4 files in a folder and formats them to be the same ratio and framerate to simplify concating.

  This is what I have so far.

  #!/bin/bash
  
  NUMBER=0
  
  MP=".mp4"
  
  OUT="./Media/Rescaled/"
  
  for filename in ./Media/*.mp4; do
  
      echo "$filename"
  
      NAME=$(basename "$filename" .mp4)
  
      NEWNAME=$NAME$NUMBER$MP
  
      let "NUMBER += 1"
  
      ffmpeg -i "$filename" -y -r 24 -vf scale=640:640  $OUT$NEWNAME
  
  done

  I receive 2 errors that I can’t really get my head around as of now :

  The encoder 'aac' is experimental but experimental codecs are not enabled,                 
  
  add '-strict -2' if you want to use it.

  which I first of all am not sure where to put in and second of all have heard it messes with audio quality and

  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x19434c0] Format mov,mp4,m4a,3gp,3g2,mj2  
  
  detected only with low score of 1, misdetection possible!
  
  
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x19434c0] moov atom not found
  
  ./Media/Whitenoise.mp4: Invalid data found when processing input

  I am absolutely a novice at this, so I would appreciate answers with an explanation or pointing me to something that explains it well as I’ve been having trouble finding good ffmpeg material.

  Thanks for reading through this !

• Converting AC3 to AAC with minimal loss [on hold]

  20 juin 2016, par forthrin

  iPad does not seem to support the ac3 audio codec.

  Therefore, I am converting an mkv/h264/ac3 movie into m4v/m264/aac using ffmpeg to view it on the iPad.

  The video part is simply copied as it is ; my question is how I preserve the audio as best possible.

  1. Is there any way to do the audio conversion losslessly ?

  2. If no to question 1, what is the best way to preserve the audio quality ? If the source audio is 192 kb/s and 48000 Hz, should I simply use 192/48000 for the target too ? Or will I preserve the audio better if I increase the the bit rate somewhat ?

  3. Side question : I noticed that a lot of mkv files have rather poor audio to begin with. Will the loss of ac3/aac re-encoding be negligable compared to the initial quality loss from the source material ? And why isn’t high audio quality more of a priority for movie files ? It’s not like file sizes matter much anymore with today’s storage and bandwidth.

• exporting ogg videos from video slideshow (mp4) and audio (wav) using ffmpeg in python

  17 septembre 2018, par jtz

  I have tried to find a solution already, but just cannot make it work. I want to export an .ogg-video by combining a video slideshow (mp4) with an audio file (wav) by using ffmpeg in python. The audio is shorter than the video and should have an offset of 2000 milliseconds, so that it starts approximately in the middle of the video. The code that I tried is essentially this :

  subprocess.call(’ffmpeg.exe -itsoffset 0 -i slideshows/slideshow.mp4 -itsoffset 2000 -i sounds/audio.wav -codec:v libtheora -codec:a libvorbis output.ogg’, shell= True)

  FYI : I need to create a couple of different video formats from the video and audio input, so substituting the ogg with a different format is no option. I have already successfully created .mp4-video-files and .webm-video-files from the material, but need the .ogg in addition. Also, Power Point does not like any of the exported videos, maybe this might be relevant for finding the problem here (I also unsuccessfully tried to fix this issue).