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• Can any part of an ffmpeg command use expressions?

  6 April 2022, by corgrath

  I am still learning how expressions work with ffmpeg, whether any part of a command can be using expression or not.

  


  As an example, I have this command:

  


  ffmpeg -y -i input.mp3 -af "sofalizer=sofa=ClubFritz1.sofa:type=freq:radius=2:speakers='FL 45|FR 45|BL 45|BR 45'" output.mp3

  


  (The file CubFritz1.sofa can by the way be downloaded here)

  


  Which basically applies the sofalizer effect and specify that each channel should be heard / come from, the left side (45 degrees) of the audio.

  


  This works as expected.

  


  However, I cannot seem to get expressions working in the command at all.

  


  For example this:

  


  ffmpeg -y -i input.mp3 -af "sofalizer=sofa=ClubFritz1.sofa:type=freq:radius=2:speakers='FL if(0, 45, 45)'|'FR if(0, 45, 45)'|'BL if(0, 45, 45)'|'BR if(0, 45, 45)'" output.mp3

  


  Which does an if(0, 45, 45) as a test, so regardless the outcome should be 45, right?

  


  However, when I run this command, it does not seem to work anymore, meaning the sound is not purely coming from the left side.

  


  I have even tried changing the location of the single ' in the command without luck:

  


  ffmpeg -y -i input.mp3 -af "sofalizer=sofa=ClubFritz1.sofa:type=freq:radius=2:speakers=FL 'if(0, 45, 45)'|FR 'if(0, 45, 45)'|BL 'if(0, 45, 45)'|BR 'if(0, 45, 45)'" output.mp3

  


  My question is, what are the rules for getting expressions working in an ffmpeg command?

  


  How would the command be rewritten so that the if(0, 45, 45) works?

  


• How to improve quality and latency in FFmpeg

  3 August 2020, by Andrew

  I'm trying to stream FFmpeg over the new SRT protocol that's supported as an output. For now though, I'm sending it in the form of FFmpeg -> UDP -> SRT -> SRT -> UDP -> MPV/FFmpeg.

  


  Somewhere along the line, the quality degrades sharply, and latency increases by quite a bit. This seemed to happen when adding audio. Meaning, if streaming just video, quality is decent and latency is low. If streaming just audio, quality is great but latency is high.

  


  Not sure where I'm going wrong with this, so any help would be appreciated. The main focus points is high quality low latency.

  


  ---

  


  Recording video through:

  


  ./ffmpeg.exe -rtbufsize 2147M -f dshow -i video="":audio="" -flush_packets 0 -preset medium -tune zerolatency -f mp4 -b:v 6M -g 30 -f mpegts udp://127.0.0.1:9001?pkt_size=1316


  


  or

  


  ./ffmpeg.exe -f dshow -analyzeduration 200k -probesize 6M -i video="":audio="" -flush_packets 0 -preset fast -tune zerolatency -b:v 5M -b:a 384K -c:a libopus -g 25 -f mpegts udp://127.0.0.1:9001?pkt_size=1316


  


  ---

  


  Then when taking it back at the receiver side, I use one of:

  


  ./ffmpeg.exe -i udp://127.0.0.1:9001 -c copy -bufsize 32M -f mpegts udp://127.0.0.1:9002?bitrate=26214400
./mpv.exe udp://127.0.0.1:9002


  


  or

  


  ./mpv.exe --no-cache --untimed --no-demuxer-thread --video-sync=audio --vd-lavc-threads=1 udp://127.0.0.1:9002


  


  ---

  


  What am I missing? As is quality is generally terrible and latency can get up to 10 seconds. Is it just not possible with this set up?

  


• Merge commit ’715f139c9bd407ef7f4d1f564ad683140ec61e6d’

  23 March 2017, by Clément Bœsch

  Merge commit ’715f139c9bd407ef7f4d1f564ad683140ec61e6d’
  * commit ’715f139c9bd407ef7f4d1f564ad683140ec61e6d’: (23 commits)
  
    vp9lpf/x86: make filter_16_h work on 32-bit.
  
    vp9lpf/x86: make filter_48/84/88_h work on 32-bit.
  
    vp9lpf/x86: make filter_44_h work on 32-bit.
  
    vp9lpf/x86: make filter_16_v work on 32-bit.
  
    vp9lpf/x86: make filter_48/84_v work on 32-bit.
  
    vp9lpf/x86: make filter_88_v work on 32-bit.
  
    vp9lpf/x86: make filter_44_v work on 32-bit.
  
    vp9lpf/x86: save one register in SIGN_ADD/SUB.
  
    vp9lpf/x86: store unpacked intermediates for filter6/14 on stack.
  
    vp9lpf/x86: move variable assigned inside macro branch.
  
    vp9lpf/x86: simplify ABSSUM_CMP by inverting the comparison meaning.
  
    vp9lpf/x86: remove unused register from ABSSUB_CMP macro.
  
    vp9lpf/x86: slightly simplify 44/48/84/88 h stores.
  
    vp9lpf/x86: make cglobal statement more conservative in register allocation.
  
    vp9lpf/x86: save one register in loopfilter surface coverage.
  
    vp9lpf/x86: add ff_vp9_loop_filter_[vh]_44_16_sse2,ssse3,avx.
  
    vp9lpf/x86: add ff_vp9_loop_filter_h_48,84_16_sse2,ssse3,avx().
  
    vp9lpf/x86: add an SSE2 version of vp9_loop_filter_[vh]_88_16
  
    vp9lpf/x86: add ff_vp9_loop_filter_[vh]_88_16_ssse3,avx.
  
    vp9lpf/x86: add ff_vp9_loop_filter_[vh]_16_16_sse2().
  
    ...
  All these commits are cherry-picks from FFmpeg. Maybe some slight
  
  differences sneaked in but the Libav codebase still differs too much
  
  with our own to make a proper diff. This merge is a noop.
  Merged-by: Clément Bœsch <u@pkh.me>