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• ffmpeg : recording audio + video into separate files, pressing 'q' or ctrl-C, audio is truncated

  9 août 2018, par zzzeek

  Trying to record from the camera and sound card at the same time. If I use the "-t" option with a fixed time, both streams come out fine. If I try to break out while it’s recording, by pressing either ’q’ or ctrl-C, the audio stream is cut typically 5 seconds short.

  I’ve tried many many options, codecs, -presets, combinations of everything, changing the order of the streams, usually with no luck. the thing that works the "best" is -preset ultrafast -threads 0, however I find when using these options, the program doesn’t exit cleanly and I can’t find documentation for what "-threads 0" really means (even though its name seems obvious).

  Here’s the basic command :

  ffmpeg -y -f alsa -i default -f v4l2 -framerate 25 -video_size 640x480 -i /dev/video0 -map 0:a out.wav -map 1:v out.mkv

• Non-optimal video scaling using ffmpeg

  11 septembre 2018, par Question

  I’m using ffmpeg, calling it via python, essentially I do :

  file = "c:/video/video.mp4"
  
  hd = 'ffmpeg -y -i % s -crf 23 -preset fast -c: a copy verifast480_output.mp4'% file
  
  os.system (hd)

  The aim would be to make a good video resize for minor quality, such as a video from 720p to 480p.

  But in rehearsing I thought of turning a 720p video into another one of the same size, to see how it was getting better or worse.

  Here are the problems encountered :
  The resulting videos are larger than the original( For example, a file of 220 Mb then becomes 250 Mb at the end of the transformation ), and sometimes even longer than a few seconds( if the video lasts 22:15 at the end of the transformation it becomes 22:22 ).

  For example this command is not as written in the documentation :
  "-crf" possible values 0-51, but if I put "-crf 0" (means no loss of quality) the video from 250 Mb becomes over 1 Gb, only with this option.

  What interested me was a way to preserve the original appearance as much as possible.

• (ffmpeg) : Failed to read frame size : Could not seek to 1026

  24 mai 2021, par UserUNP

  I was trying to convert Midi files to Mp3 files using timidity and ffmpeg
using this command

  


  python -m timidity play.mid -Ow -o - | ffmpeg -i - -acodec libmp3lame -ab 64k play.mp3


  


  so I can use it in my Discord bot, but whenever I execute the command, it always returns this error that I couldn't understand

  


  [mp3 @ 0x56226d7e0440] Format mp3 detected only with low score of 1, misdetection possible!
[mp3 @ 0x56226d7e0440] Failed to read frame size: Could not seek to 1026.
play.mp3: Invalid argument


  


  If you have any idea to what this means or how can I fix it then please give me an Answer, thanks !