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• Envelope pattern in SoX (Sound eXchange) or ffmpeg

  26 mai 2016, par pJay

  I’ve been using SoX to generate white noise. I’m after a way of modulating the volume across the entire track in a way that will create a pattern similar to this :

  White noise envelope effect

  I’ve experimented with fade, but that fades in to 100% volume and fades out to 0% volume, which is just a pain in this instance.

  The tremolo effect isn’t quite what I’m after either, as the frequency of the pattern will be changing over time.

  The only other alternative is to split the white noise file into separate files, apply fade and then apply trim to either end so it doesn’t fade all the way, but this seems like a lot of unnecessary processing.

  I’ve been checking out this example Using SoX to change the volume level of a range of time in an audio file, but I don’t think it’s quite what I’m after.

  I’m using the command-line in Ubuntu with SoX, but I’m open to suggestions with ffmpeg, or any other Linux based command-line solution.

• Having ffmpeg add a repeating text overlay on a video

  30 mai 2020, par Caius Jard

  I'm looking to create an overlay that cycles through the characters in a string over and over. I've succeeded in using a sendcmd file to put A, B, C, D, E on the first 5 seconds of a video

  



  0  drawtext reinit 'text=A';
1  drawtext reinit 'text=B';
2  drawtext reinit 'text=C';
3  drawtext reinit 'text=D';
4  drawtext reinit 'text=E';


  



  But it doesn't cycle and I haven't been able to find a way to make it, because sendcmd looks like it just takes a simple timecode. I could make a command file 3600 lines long for my hour video, with those commands in over and over (the command file would be generated programmatically so not onerous)

  



  ---

  



  After some considerable experimenting I was able to do it with 5 separate drawtext :

  



  drawtext=fontfile=/Windows/Fonts/bauhs93.ttf:fontsize=1024:fontcolor=white@0.1:bordercolor=black@0.1:borderw=10:r=250:text='A':x=if(trunc(mod(t\,5))\,-2000\,(w-tw)/2),
drawtext=fontfile=/Windows/Fonts/bauhs93.ttf:fontsize=1024:fontcolor=white@0.1:bordercolor=black@0.1:borderw=10:r=250:text='B':x=if(trunc(mod(t\,5))-1\,-2000\,(w-tw)/2),
drawtext=fontfile=/Windows/Fonts/bauhs93.ttf:fontsize=1024:fontcolor=white@0.1:bordercolor=black@0.1:borderw=10:r=250:text='C':x=if(trunc(mod(t\,5))-2\,-2000\,(w-tw)/2),
drawtext=fontfile=/Windows/Fonts/bauhs93.ttf:fontsize=1024:fontcolor=white@0.1:bordercolor=black@0.1:borderw=10:r=250:text='D':x=if(trunc(mod(t\,5))-3\,-2000\,(w-tw)/2),
drawtext=fontfile=/Windows/Fonts/bauhs93.ttf:fontsize=1024:fontcolor=white@0.1:bordercolor=black@0.1:borderw=10:r=250:text='E':x=if(trunc(mod(t\,5))-4\,-2000\,(w-tw)/2)


  



  But as can be seen, I have to repeat a lot of stuff here. Is there any slicker way ? It does seem to have a noticeable effect on encoding speed the more chars are added

  



  I was hoping that text expressions would help but it seems I can only return numerics from the values, so this expression didn't work out :

  



  %{e:if(trunc(mod(t,5)),'A', '')%{e:if(trunc(mod(t,5))-1,'B', '') ...


  


• ffmpeg won't livestream to youtube

  4 novembre 2019, par HeyItsDan

  I’m trying to write a simple "script" that allows me to stream a music radio to YouTube or any other platform but whenever I’m trying to test it, it won’t let me livestream at all, if anyone got a solution to this it would be very appreciated !

  StreamURL="xxxxxxxxxxxxxxxxxxxx"
  
  Key="xxxxxxxxxxxxxxxxxxxxxxxx"
  
  BackgroundPath="bg.jpg"
  
  NPPath="np.txt"
  
  
  
  ffmpeg \
  
  -re \
  
  -loop 1 \
  
  -framerate $FPS \
  
  -i $BackgroundPath \
  
  -s 1920x1080 \
  
  -ab 128k \
  
  -maxrate 2048k \
  
  -bufsize 2048k \
  
  -vf "drawbox=0:0:1920:100:black:fill, drawtext='fontfile=Arial\:style=Bold Italic:text=Now Playing':fontcolor=white:fontsize=35:x=20:y=20, drawtext=textfile='$NPPath':fontcolor=white:fontsize=28:x=20:y=58" \
  
  -c:a aac \
  
  -f flv $StreamURL$Key```