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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 ?

  


• Revision 7c70145914 : Merge "Add col/row-based coefficient scanning patterns for 1D 8x8/16x16 ADSTs."

  27 mars 2013, par Ronald S. Bultje

  Changed Paths : Modify /vp9/encoder/vp9_rdopt.c Merge "Add col/row-based coefficient scanning patterns for 1D 8x8/16x16 ADSTs." into experimental

• ffmpeg timecode based on filename

  9 mars 2023, par marven

  I have xxxxx videofiles that need to get a timecode (for working in premiere)
The filenames are all like this 2023-03-08 12.59.59 AndSomeRandowNumbers.
Is that possible with ffmpeg ?
Or if that is not possible : can ffmpeg use an other date from the metadata and use that as timecode (with exiftool is possible to use the filename and write it as creation date, and other, but not as timecode) ?

  


  ffmpeg -i file.mov -map 0 -map -0:d -c copy -timecode 02:10:22:33 outputfile.mov
that is the code that works to change the timecode to 02:10:22:33