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• ffmpeg : Downmixing 5.1 to stereo with phase invert

  1er novembre 2022, par anti-hero

  I'd like to use ffmpeg and Dolby Logic Pro II formula to downmix a 5.1 song to stereo :

  


  


  Lt = L + (–3 dB × C) – (–1.2 dB × Ls) – (–6.2 dB × Rs)

  


  Rt = R + (–3 dB × C) + (–6.2 dB × Ls) + (–1.2 dB × Rs)

  


  


  I came up with this long and probably redundant bash script :

  


  # L channel
ffmpeg -i "$filename" -map_channel 0.1.0 -c:a pcm_f32le L.wav
ffmpeg -i "$filename" -map_channel 0.1.2 -filter:a "volume=-3dB" -c:a pcm_f32le C.wav
ffmpeg -i "$filename" -map_channel 0.1.4 -af "volume=-1.2dB" -c:a pcm_f32le Ls.wav
ffmpeg -i "$filename" -map_channel 0.1.5 -af "volume=-6.2dB" -c:a pcm_f32le Rs.wav
ffmpeg -i Ls.wav -af "aeval=-val(0)" -c:a pcm_f32le Lsi.wav
ffmpeg -i Rs.wav -af "aeval=-val(0)" -c:a pcm_f32le Rsi.wav
ffmpeg -i L.wav -i C.wav -i Lsi.wav -i Rsi.wav -filter_complex "amix=inputs=4" -c:a pcm_f32le L_final.wav
rm L.wav Ls.wav Rs.wav Lsi.wav Rsi.wav

# R channel
ffmpeg -i "$filename" -map_channel 0.1.1 -c:a pcm_f32le R.wav
ffmpeg -i "$filename" -map_channel 0.1.4 -filter:a "volume=-6.2dB" -c:a pcm_f32le Ls.wav
ffmpeg -i "$filename" -map_channel 0.1.5 -filter:a "volume=-1.2dB" -c:a pcm_f32le Rs.wav
ffmpeg -i R.wav -i C.wav -i Ls.wav -i Rs.wav -filter_complex "amix=inputs=4" -c:a pcm_f32le R_final.wav
rm R.wav C.wav Ls.wav Rs.wav

# Mix
ffmpeg -i L_final.wav -i R_final.wav -filter_complex "[0:0][1:0] amerge=inputs=2" -c:a pcm_f32le "${filename%.*}_dm.wav"
rm L_final.wav R_final.wav


  


  Would this work ? And is there a simpler way to do this ?

  


  update : I also wrote Python code for the 90 degree phase shift version.

  


  import scipy, os, numpy as np

os.system(f'ffmpeg -i "{filename}" -c:a pcm_f32le temp.wav')
sample_rate, waves = scipy.io.wavfile.read("temp.wav")
os.remove("temp.wav")

L, R, C, LFE, LS, RS = waves.T

LS_shifted = -np.imag(scipy.signal.hilbert(LS))
RS_shifted = np.imag(scipy.signal.hilbert(RS))
L_out = L + 0.708 * C - 0.871 * LS_shifted - 0.49 * RS_shifted
R_out = R + 0.708 * C + 0.49 * LS_shifted + 0.871 * RS_shifted

scipy.io.wavfile.write("out.wav", sample_rate, np.vstack((L_out, R_out)).T)


  


  Hope someone finds this useful ! (and that someone verifies it's correct)

  


• cannot find ffmpeg in videoshow in nodejs

  6 novembre 2019, par Sunil Garg

  I want to create video from image files. So I have installed videoshow module. And configured the same as per the documentaion.

  var videoOptions = {
  
    fps: 25,
  
    loop: 5, // seconds 
  
    transition: true,
  
    transitionDuration: 1, // seconds 
  
    videoBitrate: 1024,
  
    videoCodec: 'libx264',
  
    size: '640x?',
  
    audioBitrate: '128k',
  
    audioChannels: 2,
  
    format: 'mp4',
  
    pixelFormat: 'yuv420p'
  
  }
  
  
  
  var images = [
  
    "D:/PROJECTS/Video/storage/1.jpg",
  
    "D:/PROJECTS/Video/storage/2.jpg"
  
  ];
  
  
  
  app.get("/video", function () {
  
    videoshow(images, videoOptions)
  
      // .audio('song.mp3')
  
      .save('video.mp4')
  
      .on('start', function (command) {
  
        console.log('ffmpeg process started:', command)
  
      })
  
      .on('error', function (err, stdout, stderr) {
  
        console.error('Error:', err)
  
        console.error('ffmpeg stderr:', stderr)
  
      })
  
      .on('end', function (output) {
  
        console.error('Video created in:', output)
  
      })
  
  });

  But When I run it shows the error on server

  Error: Error: Cannot find ffmpeg
  
      at D:\PROJECTS\Video\node_modules\videoshow\node_modules\fluent-ffmpeg\lib\processor.js:136:22
  
      at D:\PROJECTS\Video\node_modules\videoshow\node_modules\fluent-ffmpeg\lib\capabilities.js:123:9
  
      at D:\PROJECTS\Video\node_modules\videoshow\node_modules\async\dist\async.js:473:16
  
      at next (D:\PROJECTS\Video\node_modules\videoshow\node_modules\async\dist\async.js:5315:29)
  
      at D:\PROJECTS\Video\node_modules\videoshow\node_modules\async\dist\async.js:958:16
  
      at D:\PROJECTS\Video\node_modules\videoshow\node_modules\fluent-ffmpeg\lib\capabilities.js:116:11
  
      at D:\PROJECTS\Video\node_modules\videoshow\node_modules\fluent-ffmpeg\lib\utils.js:223:16
  
      at F (D:\PROJECTS\Video\node_modules\videoshow\node_modules\which\which.js:68:16)
  
      at E (D:\PROJECTS\Video\node_modules\videoshow\node_modules\which\which.js:80:29)
  
      at D:\PROJECTS\Video\node_modules\videoshow\node_modules\which\which.js:89:16

  Then I installed ffmpeg using

  npm install ffmpeg --save

  but not worked. So I tried installing at the global level using

  npm install ffmpeg -g

  Even installing on my window machine and setting the path of its bin folder in environment variables did not work ?

  What could be the issue ?

• Automatic encoder selection failed Default encoder for format mp3 is probably disabled. Please choose an encoder manually.Error selecting an encoder

  27 janvier 2018, par Parimal Desai

  using ffmpeg compressing song to low quality getting error for

  "Automatic encoder selection failed for output stream #0:1. Default encoder for format mp3 (codec mp3) is probably disabled. Please choose an encoder manually. Error selecting an encoder for stream 0:1"

  ffmpeg -i /home/smubu/public_html/uploads/tracks/47865540_1999341734_1027911481.mp3 -ab 64 /home/smubu/public_html/uploads/tracks/47865540_1999341734_1027911481_comp_96.mp3
  
  
  
  ffmpeg version 3.4.1 Copyright (c) 2000-2017 the FFmpeg developers
  
    built with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-18)
  
    configuration:
  
    libavutil      55. 78.100 / 55. 78.100
  
    libavcodec     57.107.100 / 57.107.100
  
    libavformat    57. 83.100 / 57. 83.100
  
    libavdevice    57. 10.100 / 57. 10.100
  
    libavfilter     6.107.100 /  6.107.100
  
    libswscale      4.  8.100 /  4.  8.100
  
    libswresample   2.  9.100 /  2.  9.100
  
  [mp3 @ 0x218e380] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, mp3, from '/home/smubu/public_html/uploads/tracks/47865540_1999341734_1027911481.mp3':
  
    Metadata:
  
      encoder         : LAME 32bits version 3.98.2 (http://www.mp3dev.org/)
  
      title           : Dj.Senior'B Kantinti [Club Rmx
  
      track           : 2010
  
      comment         : Downloaded from Howwe Entertainment [ www.howwe.biz ]
  
      TEXT            : 2010
  
      TLEN            : 97391548
  
      artist          : Stecia Mayanja
  
      album_artist    : www.howwe.biz
  
      composer        : www.howwe.biz
  
      album           : Howwe Entertainment
  
      genre           : www.howwe.biz
  
      date            : 2010
  
    Duration: 00:03:46.34, start: 0.000000, bitrate: 81 kb/s
  
      Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 80 kb/s
  
      Stream #0:1: Video: png, rgba(pc), 600x600, 90k tbr, 90k tbn, 90k tbc
  
      Metadata:
  
        comment         : Other
  
  Automatic encoder selection failed for output stream #0:1. Default encoder for format mp3 (codec mp3) is probably disabled. Please choose an encoder manually.
  
  Error selecting an encoder for stream 0:1

  Help me regarding this issue