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• Android ffmpeg simple JNI wrapper

  12 octobre 2012, par user1504495

  I've been trying to use an ffmpeg binary with command line access for a while now and getting nowhere (Using runtime.exec)
  It looks like the only way I'll be able to get it to work is using a wrapper in C to access the built ffmpeg libraries using JNI...
  Main problem : I haven't coded C for more than one and a half decades now and wouldn't know where to begin...

  I just need 3 operations, I need to add audio to a video file, I need to concatenate two video files and if possible I need to rotate a clip by 90 degrees (but I could do without this)...

  Does anyone have any example code that could work for me, or some good places to start (I've already exhausted much of the first pages of various google results to no avail)...

  Any help would be greatly appreciated !

• Android ffmpeg simple JNI wrapper

  15 juin 2017, par user1504495

  I’ve been trying to use an ffmpeg binary with command line access for a while now and getting nowhere (Using runtime.exec)
  It looks like the only way I’ll be able to get it to work is using a wrapper in C to access the built ffmpeg libraries using JNI...
  Main problem : I haven’t coded C for more than one and a half decades now and wouldn’t know where to begin...

  I just need 3 operations, I need to add audio to a video file, I need to concatenate two video files and if possible I need to rotate a clip by 90 degrees (but I could do without this)...

  Does anyone have any example code that could work for me, or some good places to start (I’ve already exhausted much of the first pages of various google results to no avail)...

  Any help would be greatly appreciated !

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

  17 mai 2024, par Wes Modes

  I am procedurally constructing complexFilters for ffmpeg via fluent-ffmpeg. 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.

  


  Here I'm testing on the command line, to understand the mysteries of lightly-documented ffmpeg filters. I'm fading in and out two sources, intertwined in the output. Now I want to apply lowpass, highpass, aphaser, and/or aecho to the transitions using a time-based expr.

  


  I've already succeeded using the volume filter to fade the sources in and out (Note that the sine has reversed polarity for the second volume filter) :

  


  # 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


  


  ffmpeg -filters says that lowpass 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 these other filters to source1 using a time-bassed expr ? I was unsuccessful in figuring out lowpass and highpass :

  


  # applying a lowpass filter
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, \
    lowpass=f=3000: mix='0.5 + 0.5 * cos(PI * t / 5)' \
    [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


  


  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 ?