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• ffmpeg record audio from Xvfb on Centos

  25 mai 2017, par boygiandi

  I’m trying to record audio from Xvfb. And I have some problems :

  1. What’s the different between alsa and pulse. I get confuse
  2. Server Centos have no soud card :

  arecord -l

  arecord : device_list:268 : no soundcards found...

  3. I may have many Xvfb process, how to record video and audio from specific Xvfb process. I checked this https://trac.ffmpeg.org/wiki/Capture/ALSA#Recordaudiofromanapplication but still don’t understand how it works.

  ffmpeg -f alsa -ac 2 -i hw:0,0 -acodec pcm_s16le output.wav

  I seen many command like this, but I don’t know how to get hw:0,0 ( id of sound card ? )

  Please help. Thanks

• FFmpeg overlay filter_complex is slow on Android

  15 septembre 2019, par nor0x

  I’m using FFmpeg on Android (Xamarin) to add a watermark to a video. I have tested the operation with multiple videos and i think overall performance is pretty bad. I wanted to share my results and see how if anyone has similar or better benchmarks.

  I’m using the following command for adding a png watermark to the video.

  $"-i {video} -i {watermark} -filter_complex \"overlay=W-w-5:H-h-5\" -codec:a copy -preset ultrafast -loglevel debug {output} -y";

  The watermark is a 150x150 png with a filesize of 18KB.

  Video 1
  - 13 seconds
  - 3840x2160
  - 60FPS
  - 125MB
  FFmpeg duration : 156 seconds

  Video 2
  - 4 seconds
  - 3840x2160
  - 30FPS
  - 17MB
  FFmpeg duration : 35 seconds

  Video 3
  - 10 seconds
  - 1920x1080
  - 60FPS
  - 35MB
  FFmpeg duration : 79 seconds

  What do you think of these results, is it legit that adding an overlay takes that long ? Maybe there is something wrong with my command ? I ran these tests on an Asus Zenfone 6 (Snapdragon 855, 8GB RAM)

  EDIT :
  I’m using FFmpeg version 3.0.1.1 compiled for ARM. (https://github.com/gperozzo/XamarinAndroidFFmpeg/tree/master/binary/3.0.1.1/arm).

  All videos are mp4 files with the H.264 format.

• Python Subprocess.Popen or os.popen

  21 septembre 2023, par Nowski

  hi I want to run a bash command in my script to process a file with ffmpeg, I am struggling to get it to work in subprocess or os

  


  I build my command from variables elsewhere in the script and the resulting string is a legit ffmpeg call :

  


  fcommand=(f'/usr/bin/ffmpeg -i   {inputf}  -b:a  128K -vn  {output_directory}{youtube_id}.mp3')

Print(fcommand)  result: /usr/bin/ffmpeg -i   /media/pi/VDRIVE/uploaded/gf23_pmc-speakers.mp4  -b:a  128K -vn  /media/pi/VDRIVE/audio/EN6_KfsEtdM.mp3

os.popen(fcommand)


  


  This works, sorta. - eg I can see the output from FFmpeg on the shell I am running my parent python script with (python3 myscript.py)

  


  However, the parent python script just pauses and doesnt do anything further.
So I tried :

  


  subprocess.Popen(fcommand)


  


  But now I get the python error :

  


  [Errno 2] No such file or directory: [Errno 2] No such file or directory: 'ffmpeg -i   /media/pi/VDRIVE/uploaded/gf23_pmc-speakers.mp4  -b:a  128K -vn  /media/pi/VDRIVE/audio/EN6_KfsEtdM.mp3': 'ffmpeg -i   /media/pi/VDRIVE/uploaded/gf23_pmc-speakers.mp4  -b:a  128K -vn  /media/pi/VDRIVE/audio/EN6_KfsEtdM.mp3'


  


  My aim is to have the Python script run, make the file from FFMPEG input then move on to another step in the script.
Bashing my head against the wall here...