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• lavfi/fifo : fix flushing when using request_samples

  4 août 2013, par Anton Khirnov

  lavfi/fifo : fix flushing when using request_samples
  If any samples are still buffered when request_frame returns EOF, they
  
  won’t be returned currently.
  

  • [DH] libavfilter/fifo.c

• Audio clicks / cracklings with ffmpeg audio recording on mac os

  15 février 2023, par Specimen

  I'm having audio clicks on my ffmpeg audio recordings. If I record with OBS for example, the audio comes out just fine. This is what I put in the terminal :

  


  ffmpeg -f avfoundation -i ":0" test.mp3


  


  where 0 is my Soundflower audio device, which I found using ffmpeg -f avfoundation -list_devices true -i "", which returns :

  


  AVFoundation audio devices:
[0] Soundflower (2ch)


  


  Soundflower, my speakers, and the ffmpeg recording are all set at 48kHz.
There is another thread that states that this may be an issue with ffmpeg version 4.3, and to try to downgrade to 4.2 ; I tried to google how to downgrade on brew, but didn't find anything.

  


• ffmpeg quality conversion options (video compression)

  25 septembre 2020, par Jason Hunter

  Can you provide a link, or an explanation, to the -q:v 1 argument that deals with video/image quality, and compression, in ffmpeg.

  


  Let me explain...

  


  for f in *
   do 
     extension="${f##*.}"
     filename="${f%.*}"
     ffmpeg -i "$f" -q:v 1 "$filename"_lq."$extension"
     rm -f "$f"
   done


  


  The ffmpeg for loop above compresses all images and videos in your working directory, it basically lowers the quality which results in smaller file sizes (the desired outcome).

  


  I'm most interested in the -q:v 1 argument of this for loop. The 1 in the -q:v 1 argument is what controls the amount of compression. But I can't find any documentation describing how to change this value of 1, and describing what it does. Is it a percentage ? Multiplier ? How do I adjust this knob ? Can/should I use negative values ? Integers only ? Min/max values ? etc.

  


  I started with the official documentation but the best I could find was a section on video quality, and the -q flag description is sparse.

  


  


  -frames[:stream_specifier] framecount (output,per-stream)
  
Stop writing to the stream after framecount frames.
  
.
  
-q[:stream_specifier] q (output,per-stream)
  

  
-qscale[:stream_specifier] q (output,per-stream)
  
Use fixed quality scale (VBR). The meaning of q/qscale is codec-dependent. If qscale is used without a stream_specifier then it applies only to the video stream, this is to maintain compatibility with previous behavior and as specifying the same codec specific value to 2 different codecs that is audio and video generally is not what is intended when no stream_specifier is used.