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• FFMPEG filter instances names don't work with "sendcmd" ?

  13 septembre 2023, par VladStepu2001

  I have two drawbox filter instances that I need to animate separately.
  
I've used sendcmd for the one instance already, and it worked fine.

  


  But when I've added the second one, I gave a name to both of them like this :

  


  drawbox@one=0:0:iw:ih:red:fill,drawbox@two=0:0:iw:ih:black:fill


  


  Then, I've tried to use sendcmd like this :

  


  drawbox@one=0:0:iw:ih:red:fill,drawbox@two=0:0:iw:ih:black:fill,
sendcmd=c='0.0-5.0 [expr] drawbox@one w W*(T/5)
           0.0-5.0 [expr] drawbox@two h H*(T/5)'


  


  But that didn't work, the rectangles stayed still.

  


  What I am doing wrong ?

  


• Why failes ffmpeg with "Failed to inject frame into filter network : Internal bug, should not have happened" ?

  17 octobre 2023, par StackOverRigge

  I want to convert a MP4 video file into an animated gif file using ffmpeg. I am trying to do this in two steps :

  


  

  1. Create a palette image

  


  2. Convert the MP4 with the help of the palette image to a GIF file

  


  


  I'm using ffmpeg 6.0 essentials_build.

  


  First, I create a palette image :

  


  ffmpeg -v warning -i video.mp4 -vf "fps=15,scale=1366:768:flags=lanczos,palettegen=stats_mode=diff" -y palette.png


  


  Then, I'm trying to convert the MP4 to GIF :

  


  ffmpeg -i video.mp4 -i palette.png -lavfi "fps=15,scale=1366:768:flags=lanczos,paletteuse=dither=bayer:bayer_scale=5:diff_mode=rectangle" -y video.gif


  


  This command ends in this error message :

  


  Error while filtering: Internal bug, should not have happeneditrate=4279.9kbits/s speed=0.742x
Failed to inject frame into filter network: Internal bug, should not have happened
Error while processing the decoded data for stream #0:0


  


• How to mimic Audacity's "truncate silence" with ffmpeg "silenceremove" filter

  16 juin 2024, par Cara Duf

  I want to remove completely silence parts from wav files with ffmpeg.

  


  Input wav can be like :


  


  I am using the following ffmpeg command to remove silence part ffmpeg -i input.wav -af silenceremove=stop_periods=-1:stop_duration=0.2:stop_threshold=-45dB output.wav because I understand from the doc that it will remove all silence parts longer than 0.2 s (silence being below -45dB).

  


  But I get that where silence part has only been reduced to around 0.1 wheras I want it to be 0 (no remaining silence).

  


  In Audacity I will use "truncate audio" filter and choose the above parameters to detect silence and in the action part I will choose to truncate to 0 : .

  


  This will yield to what I want (ie an audio with no silence part remaining) :


  


  Searching on the internet only lead me to what I already do.

  


  So how can I reproduce the output I get from Audacity "Truncate Silence" filter with ffmpeg and remove all silence parts from audio ?

  


  Edit : The output from silencedetect filter is correct : ffmpeg -i input.wav -af silencedetect=0.2:n=-45dB -f null - detects exactly what audacity detects.

  


  Thanks in advance for your help