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• How do I mix multiple audio tracks mit FFMPEG and adjust each volume ?

  4 avril 2022, par doppelzwei

  Let's say I have an input .mp4 file that contains 4 audio tracks.
How can I change their volumes independently and convert it to a new file that just contains all the 4 audio tracks mixed together and stored in the first audio track ? For example I want the first, second and third audio tracks from the input file to be double their original volume and the fourth to be half its original volume, all saved in the output files first audio track. How would that command look like ?

  


• finding bottleneck. Ffmpeg does not utilize 800% on 4core\8threads CPU. Why ?

  3 septembre 2014, par user3652819

  I’m trying to encode video’s (using x264 codec) on E3-1245 V2 3.40GHz CPU, 32 GB RAM, 2TB 7200RPM disks (with soft Raid 1) debian 6 server

  E3-1245 V2 has 4 cores / 8 threads, but ffmpeg can’t utilize all 800%, and utilize about 200% per instance.

  I read many other threads, and people always say "Run few ffmpeg process in parallel mode"

  But where actually the bottleneck in one ffmpeg instance ? CPU bus / RAM freq. speed ??

  exec ("/usr/bin/ffmpeg -i " . $fullpath . ' -pass 1 -passlogfile    
  
  /var/www/scripts/twopass2.log -refs 1 -threads 0 -vcodec libx264 -bsf h264_mp4toannexb 
  
  -s 1280x720 -aspect 16:9 -r 24 -g 48 -keyint_min 48 -sc_threshold 0 -x264opts 
  
  "keyint=48:min-keyint=48:scenecut=0:stats=/var/www/scripts/stats2.log" -b:v 2300k -bf 0 
  
  -profile:v baseline  -mixed-refs 0 -level 30 -maxrate 80M -bufsize 80M  -acodec aac -
  
  async 1 -pix_fmt yuv420p -f mpegts  -strict -2 -ar 44100 -b:a 128k -map 0 -dn -sn -y 
  
  /dev/null');
  
  
  
  exec ("/usr/bin/ffmpeg -i " . $fullpath . ' -pass 2 -passlogfile 
  
  /var/www/scripts/twopass2.log -refs 1 -threads 0 -vcodec libx264 -bsf h264_mp4toannexb 
  
  -s 1280x720 -aspect 16:9 -r 24 -g 48 -keyint_min 48 -sc_threshold 0 -x264opts 
  
  "keyint=48:min-keyint=48:scenecut=0:stats=/var/www/scripts/stats2.log" -b:v 2300k -bf 0 
  
  -profile:v baseline  -mixed-refs 0 -level 30 -maxrate 80M -bufsize 80M  -acodec aac -
  
  async 1 -pix_fmt yuv420p -f mpegts  -strict -2 -ar 44100 -b:a 128k -map 0 -dn -sn -
  
   flags  -global_header -f segment -segment_format mpegts -segment_time 10  -
  
  segment_list /dev/null -y ' . $idpath . '2/%5d.ts');

  I think there is demuxing problem, but not sure.

  Also I tried something like this :

  mkfifo pipe.y4m
  
  ffmpeg -i input.mp4 -f yuv4mpegpipe -y pipe.y4m
  
  and run
  
  x264 -o dvd1.264 pipe.y4m

  CPU utilizing a bit better (about 150% ffmpeg and 350% - x264) but also this is not 800% at all.

  Any way to speed up encoding ?
  And where actually bottleneck there ?

• How to avoid the millisecond silence that ffmpeg adds to the beginning and end of a converted mp3 ? [on hold]

  29 décembre 2015, par Von Villamor

  I’m working on a small side project regarding splicing multiple mp3 files altogether and FFMPEG has this problem where it adds a millisecond to the beginning and the end of an audio file resulting in stops in the final mixed audio. So is there a flag or workaround available to it ?

  I’m working on hundreds and hundreds of small mp3 files so editing them one by one is next to impossible.

  Here’s a sample, the splices are at 5 seconds interval.