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• ffmpeg : Apply a time-based expression to control lowpass, highpass, aphaser, or aecho [closed]

  17 mai 2024, par Wes Modes

  I am constructing complexFilters to procedurally generate audio with ffmpeg via fluent-ffmpeg. The interesting part of my fluent-ffmpeg complex filters look like :

  


  {
   "filter": "volume",
   "options": {
       "volume": "min(1, max(0, ((cos(PI * t * 1 / 13) * 1 + cos(PI * t * 1 / 7) * 0.5 + cos(PI * t * 1 / 3) * 0.25) +
-0.5 ) * 0.75 * -1 + 0.5))",
       "eval": "frame"
    },
    "inputs": "track_1_output",
    "outputs": "track_1_adjusted"
},


  


  Note that I am using an expression to determine the volume dynamically. To simplify my tests, I'm constructing complexFilters on the command line to understand the mysteries of some of the lightly-documented ffmpeg filters. Here's a working CLI test of using the volume filter to fade the sources in and out according to a time-based expresssion :

  


  # working fade in/out
ffmpeg -i knox.mp3 -i static.mp3 -filter_complex \
"[0:a] \
    volume = 'min(1, max(0, 0.5 + 0.5 * cos(PI * t / 5)))': eval=frame \
    [a0]; \
[1:a] \
    volume = 'min(1, max(0, 0.5 - 0.5 * cos(PI * t / 5)))': eval=frame \
    [a1]; \
[a0][a1]
    amix = inputs=2: duration=shortest" \
-c:a libmp3lame -q:a 2 output.mp3


  


  Now I want to apply lowpass, highpass, aphaser, and/or aecho to the transitions using a time-based expression. For instance, looking at lowpasss, according to ffmpeg -filters it says that it has time-based support :

  


    T.. = Timeline support
 TSC lowpass           A->A       Apply a low-pass filter with 3dB point frequency.


  


  How can I similarly apply a time-based expression to lowpass, highpass, aphaser, or aecho ? I thought the mix option might be the key, but I couldn't construct a working example and couldn't find any examples.

  


  # applying a lowpass filter
ffmpeg -i knox.mp3 -filter_complex \
"[0:a] \
    lowpass=f=3000:mix='0.5 + 0.5 * cos(PI * t / 5)';" \
-c:a libmp3lame -q:a 2 output.mp3


  


  Or if you prefer the fluent-ffmpeg filter :

  


  const ffmpeg = require('fluent-ffmpeg');

ffmpeg('knox.mp3')
    .complexFilter([
        {
            filter: 'lowpass',
            options: {
                f: 3000,
                mix: '0.5 + 0.5 * cos(PI * t / 5)'
            },
            inputs: '[0:a]',
        }
    ])
    .audioCodec('libmp3lame')
    .audioQuality(2)
    .save('output.mp3')
    .on('end', () => {
        console.log('Processing finished successfully');
    })
    .on('error', (err) => {
        console.error('Error: ' + err.message);
    });


  


  With the resultant error :

  


  [Parsed_lowpass_1 @ 0x7f9a72005c00] [Eval @ 0x7ff7bec423d8] Undefined constant or missing '(' in 't/5)'
[Parsed_lowpass_1 @ 0x7f9a72005c00] Unable to parse option value "0.5 + 0.5 * cos(PI * t / 5)"
Error applying option 'mix' to filter 'lowpass': Invalid argument


  


  What complicated fffmpeg faerie magic is needed to make some of the filters other than volume controlled by a time-based expr ?

  


• avformat/mxfdec : Detect field_order based on video_line_map

  19 octobre 2016, par Tobias Rapp

  avformat/mxfdec : Detect field_order based on video_line_map
  Read video_line_map from MXF generic picture essence descriptor and use
  
  it to derive the coded field order. Use field_dominance to derive the
  
  display field order from coded field order. If field_dominance is not
  
  available the default value "1" is used as defined in SMPTE S377-1.
  Fixes field_order detection for a bunch of DV/DVCPRO files. The heuristic
  
  for deriving coded field order from video_line_map is inspired by
  
  MediaInfo.
  Signed-off-by : Tobias Rapp <t.rapp@noa-archive.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavformat/mxfdec.c

• movenc : Set tfhd default sample flags based on actual samples, if possible

  6 mars 2015, par Martin Storsjö

  movenc : Set tfhd default sample flags based on actual samples, if possible
  This avoids assuming that e.g. audio samples are marked as
  
  sync samples.
  This allows omitting the sample flags from trun, if the default
  
  flags happen to be right for all the samples.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavformat/movenc.c