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• Parallel transcoding with FFmpeg on M1 Mac

  27 août 2021, par Pushkar

  I'm trying to determine how effective an M1 Mac would be for transcoding video using FFmpeg (specifically resizing and adjusting bitrate). I can do single transcodes using a command like this :

  


  ffmpeg -I in.mp4 -nostdin -c:v h264_videotoolbox -c:a copy -vf scale=1280:720 -b:v 8000k out.mp4


  


  Now, when I run this, I can see the process in Activity Monitor, but it shows significant CPU use but 0% GPU use, although it's certainly using some form of hardware acceleration (using libx264 instead of h264_videotoolbox is much slower).

  


  When I try running multiple processes concurrently, the timings suggest little evidence of parallel execution :

  


  





  


  


  


  


  



  


  


  


  


  


  


  


  


  


  


  


  


  Test	Timing
  convert single test file	6.8s
  convert file 5 times sequentially	33.6s
  convert file 5 times in parallel	31.5s

  


  


  Since the M1 chip is supposed to have 7 or 8 GPUs inside it, I expected to see quite good parallelism, so are there options which I'm missing which would :
  

  


  

  1. ensure that the transcoding is actually running on the GPU ?

  


  2. allow parallel execution across the multiple GPUs ?

  


  


• FFMPEG Screen Capture Issue

  15 avril 2015, par William Goodwin

  Sorry if this has been solved but I couldn’t find it.

  I’m trying to screen capture using ffmpeg and stream it to Twitch. I have both x11grab and libx264 enabled but when I give it the input for my monitor it keeps returning :

  :0.0+0,0: Protocol not found

  I confirmed that :0.0 is indeed my $DISPLAY variable, and even if I call that directly in my script with the same error. My script is as follows :

  #!/bin/bash
  
  
  
  # Stream Variables
  
  STREAM_KEY="<not shown="shown">"
  
  INRES="1680x1050"
  
  OUTRES="1024x768"
  
  FPS="30"
  
  BITRATE="1266k"
  
  BUFFER="1266k"
  
  AUDIO_BITRATE="160k"
  
  
  
  ffmpeg -f alsa -ac 2 -i hw:0,0 -f x11grab -framerate $FRAMERATE -video_size $INRES \
  
     -i :0.0+0,0 -vcodec libx264 -preset veryfast -maxrate $BITRATE -bufsize $BUFFER \
  
     -vf "scale=$OUTRES, format=yuv420p" -g $(expr $FPS \* 2) -acodec libfdk_aac -b:a $AUDIO_BITRATE \
  
     -f flv rtmp://liva-jfk.twitch.tv/app/$STREAM_KEY
  
  </not>

  I’m on Debian Jessie(Testing) and ffmpeg and associated packages come from deb-multimedia. I’m curious if maybe someone here can see something I might have missed.

  Sidenote : I know the same display is called in programs like ScreenStudio and they work, but aren’t as flexible. I’ve tried using obs-studio for linux and it crashes with an illegal command when I start recording which makes me wonder if this is a system problem that might be the cause of that.

• How do I independently fade in/out multiple (3+) overlay texts over video using FFMPEG ?

  10 janvier 2019, par Balpreet_1988

  When I use this code the 1st text fades out when second text fades in. This should not happen in this code :

  I have tried the provided code in multiple ways but this is not working.

  ffmpeg -y -i title.mp4 -filter_complex "[0:v]drawtext=fontsize=100:fontfile=tst.ttf:fontcolor=0xDEB887:shadowcolor=black:shadowx=5:shadowy=5:text='Top 5 Upcoming Samsung':x=50:y=200,format=yuva444p,fade=t=in:st=0.2:d=1:alpha=1[ovr1];[ovr1:v]drawtext=fontsize=100:fontfile=tst.ttf:fontcolor=0xDEB887:shadowcolor=black:shadowx=5:shadowy=5:text='SmartPhones in 2019':x=50:y=400,format=yuva444p,fade=t=in:st=2.2:d=1:alpha=1[ovr2];[0][ovr2]overlay" test.mp4

  This should fade in 1st text at 0.2 seconds which should stay till the end of the video and 2nd text should fade in at 2.2 seconds and remain till end of video.