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• FFMPEG - How to setup volume when merging two audio streams

  6 octobre 2014, par N3sh

  I just recently entered the magic and scary world of FFMPEG and, although I found quite a lot of guides online, I need help for my current problem.

  I am merging only audio files and I would like to be able to select their volume.

  Here is my current code for merging 2 files :

  ffmpeg -i test\audio00.mp3 -i test\audio01.mp3 -filter_complex amerge 
  
  -c:a libmp3lame -q:a 0 test\output_overlay.mp3

  I tried the following code, extracted from another answer here on SO (the User was also handling video), but it doesn’t work for me :

  ffmpeg -i test\audio00.mp3 -i test\audio01.mp3 -filter_complex "[0:a]volume=0.9[a1];  
  
  [1:a]volume=0.781250[a2]; [a1][a2]amerge,pan=stereo:c0code>

  I got this error :

  [AVFilterGraph @ 030fa8c0] The following filters could not choose their formats: 
  
  Parsed_amerge_2 Consider inserting the (a)format filter near their input or output.

  Is there a simple way to change the volume for the two streams (even for just the second one, it’s the background music) with FFMPEG ?

  P.S. Also, is it possible to have some sort of ’preview’ before actually rendering the file ?

• FFMPEG - How to Extract Frames As Images While Removing Sequentially Duplicate Frames

  19 mars 2017, par Michael Nelson

  Is there any way (via script or preferably some parameter in calling ffmpeg that I missed) to extract frames from an avi file and ignore sequentially duplicate frames, thus being able to go through the pictures looking only at the deltas/changes ?

  I frequently have to record meetings at work and a lot of the time, the client screen that I am looking at is not changing while we are talking over the phone. After the meeting is over, I need to use these images as part of our documentation and specifications gathering.

  I know that I could just output every frame and run them through any given duplicate file remover utility, but this would remove ALL duplicate frames. So, if the frames extracted went like this :

  A, A, A, B, B, B, B, C, C, A, A, C, C, C, B, B, B ...

  Running them through a typical duplicate file remover, I would get : A, B, C

  What I would want is : A, B, C, A, C, B

  The command that I am currently using to extract the images is :

  ffmpeg.exe -i file.avi -ss 0 -sameq -f image2 -r 1 images%5d.png

  I was getting every frame beforehand (removing the -r 1 from above), but that was generating way too many frames to deal with since these online meetings can go for hours, so for now, I get one frame per second from the file.

  A Windows based solution would be preferable, however, I’m sure other people would be interested in solutions on other platforms if available.

  Any solution or point in the right direction is much appreciated.

• FFMPEG - How to Extract Frames As Images While Removing Sequentially Duplicate Frames

  19 octobre 2018, par Michael Nelson

  Is there any way (via script or preferably some parameter in calling ffmpeg that I missed) to extract frames from an avi file and ignore sequentially duplicate frames, thus being able to go through the pictures looking only at the deltas/changes ?

  I frequently have to record meetings at work and a lot of the time, the client screen that I am looking at is not changing while we are talking over the phone. After the meeting is over, I need to use these images as part of our documentation and specifications gathering.

  I know that I could just output every frame and run them through any given duplicate file remover utility, but this would remove ALL duplicate frames. So, if the frames extracted went like this :

  A, A, A, B, B, B, B, C, C, A, A, C, C, C, B, B, B ...

  Running them through a typical duplicate file remover, I would get : A, B, C

  What I would want is : A, B, C, A, C, B

  The command that I am currently using to extract the images is :

  ffmpeg.exe -i file.avi -ss 0 -sameq -f image2 -r 1 images%5d.png

  I was getting every frame beforehand (removing the -r 1 from above), but that was generating way too many frames to deal with since these online meetings can go for hours, so for now, I get one frame per second from the file.

  A Windows based solution would be preferable, however, I’m sure other people would be interested in solutions on other platforms if available.

  Any solution or point in the right direction is much appreciated.