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• ffmpeg replace central channel with ffmpeg

  24 mai 2020, par Rafal B

  I'm trying to replace central channel in the movie (Movie-A) with another audio stream from another movie (Movie-B).
I was able to extract stereo stream from Movie-B :

  



  ffmpeg.exe" -i "Movie-B.mkv"

Stream #0:1(pol): Audio: ac3, 48000 Hz, stereo, fltp, 320 kb/s (default)


  



  and convert it to mono stream :

  



  ffmpeg.exe" -i "Movie-B.mkv" -vn -ab 320k -ac 1 "Movie-B-Audio.ac3"
Output #0, ac3, to 'Movie-B-Audio.ac3':
Stream #0:0(pol): Audio: ac3, 48000 Hz, mono, fltp, 320 kb/s (default)


  



  For Movie-A :

  



  ffmpeg.exe" -i "Movie-B.mkv"
Stream #0:1(eng): Audio: aac (LC), 48000 Hz, 5.1, fltp (default)


  



  so Layout is 5.1 (FL+FR+FC+LFE+BL+BR), not 5.1(side) (FL+FR+FC+SL+SR)

  



  Media Info shows :

  



  Audio
ID: 2
Format: AAC
Format info: Advanced Audio Codec Low Complexity
Commercial name: AAC
Codec ID: A_AAC-2
Bit rate: 426 kb/s
Channel(s): 6 channels
Channel positions: Front: L C R, Side: L R, LFE
Channel layout: C L R Ls Rs LFE


  



  I have extracted all 6 channels into one stream with containing 6 channels :

  



  ffmpeg.exe" -i "Movie-A.mkv" -vn -ab 320k -ac 6 "Movie-A-Audio.ac3"
Output #0, ac3, to 'Movie-A-Audio.ac3':
Stream #0:0(eng): Audio: ac3, 48000 Hz, 5.1, fltp, 320 kb/s (default)


  



  But at this stage I'm getting different Layout in Movie-A-Audio.ac3 :

  



  Audio
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Commercial name                          : Dolby Digital
Duration                                 : 2 h 16 min
Bit rate mode                            : Constant
Bit rate                                 : 320 kb/s
Channel(s)                               : 6 channels
Channel layout                           : L R C LFE Ls Rs


  



  In source Movie-A.mkv it is : Channel layout : C L R Ls Rs LFE

  



  In output Movie-A-Audio.ac3 it is : Channel layout : L R C LFE Ls Rs

  



  Then I tried to extract those 6 channels into separate mono-stream files :

  



  ffmpeg.exe" -i "Movie-A-Audio.ac3" -filter_complex "channelsplit=channel_layout=5.1[FL][FR][FC][LFE][BL][BR]" -ab 320k -ac 1 -map "[FL]" extr_front_left.ac3 -ab 320k -ac 1 -map "[FR]" extr_front_right.ac3 -ab 320k -ac 1 -map "[FC]" extr_front_center.ac3 -ab 320k -ac 1 -map "[LFE]" extr_subwoofer.ac3 -ab 320k -ac 1 -map "[BL]" extr_back_left.ac3 -ab 320k -ac 1 -map "[BR]" extr_back_right.ac3


  



  With result :

  



  Stream mapping:
  Stream #0:0 (ac3) -> channelsplit
  channelsplit:FL -> Stream #0:0 (ac3)
  channelsplit:FR -> Stream #1:0 (ac3)
  channelsplit:FC -> Stream #2:0 (ac3)
  channelsplit:LFE -> Stream #3:0 (ac3)
  channelsplit:BL -> Stream #4:0 (ac3)
  channelsplit:BR -> Stream #5:0 (ac3)
Press [q] to stop, [?] for help
Output #0, ac3, to 'extr_front_left.ac3':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #0:0: Audio: ac3, 48000 Hz, mono, fltp, 320 kb/s
    Metadata:
      encoder         : Lavc58.54.100 ac3
Output #1, ac3, to 'extr_front_right.ac3':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #1:0: Audio: ac3, 48000 Hz, mono, fltp, 320 kb/s
    Metadata:
      encoder         : Lavc58.54.100 ac3
Output #2, ac3, to 'extr_front_center.ac3':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #2:0: Audio: ac3, 48000 Hz, mono, fltp, 320 kb/s
    Metadata:
      encoder         : Lavc58.54.100 ac3
Output #3, ac3, to 'extr_subwoofer.ac3':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #3:0: Audio: ac3, 48000 Hz, mono, fltp, 320 kb/s
    Metadata:
      encoder         : Lavc58.54.100 ac3
Output #4, ac3, to 'extr_back_left.ac3':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #4:0: Audio: ac3, 48000 Hz, mono, fltp, 320 kb/s
    Metadata:
      encoder         : Lavc58.54.100 ac3
Output #5, ac3, to 'extr_back_right.ac3':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #5:0: Audio: ac3, 48000 Hz, mono, fltp, 320 kb/s
    Metadata:
      encoder         : Lavc58.54.100 ac3


  



  When I'm checking channels layouts of those files extracted I see each of them is having Channel Layout marked with Central, for instant front_left.ac3 :

  



  Audio
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Commercial name                          : Dolby Digital
Duration                                 : 2 h 16 min
Bit rate mode                            : Constant
Bit rate                                 : 320 kb/s
Channel(s)                               : 1 channel
Channel layout                           : C
Sampling rate                            : 48.0 kHz


  



  Then I try to join needed channels :

  



  ffmpeg.exe" -i extr_front_left.ac3 -i extr_front_right.ac3 -i Movie-B-Audio.ac3 -i extr_back_left.ac3 -i extr_back_right.ac3 -i extr_subwoofer.ac3 -filter_complex "[0:a][1:a][2:a][3:a][4:a][5:a]join=inputs=6:channel_layout=5.1[a]" -map "[a]" "final-output.ac3


  



  But it is completely messed up : central channel (voice) is heard in front right speaker, in back right speaker is silence (or maybe it is subwoofer ?)

  



  Target is easy :

  



  

  1. convert source stereo central audio channel in Movie-B.mkv to mono channel
and

  


  2. insert it as central channel into Movie-A.mkv that have 5.1 Audio stream with layout C L R Ls Rs LFE

  


  



  So far I was able to complete 1. but I have a problem with mappings.
Can someone try to guide me how to do that ?

  


• avcodec/h2645_parse : add support for H266/VVC

  21 mars 2023, par Nuo Mi

  avcodec/h2645_parse : add support for H266/VVC
  Co-authored-by : Thomas Siedel <thomas.ff@spin-digital.com>
  
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavcodec/h2645_parse.c
  • [DH] libavcodec/vvc.h

• FFMPEG with Rails 4.2 in production

  12 février 2016, par Vincent

  I’m using FFMPEG to convert an uploaded wav file in a mp3.

  My code works in development mode but not in production and I can’t find where the error is. As far as I can tell, I think it’s a path problem with the tmp file. FFMPEG works in production (Digital Ocean) when I run a command on the terminal.

  My mp3 job :

      class Mp3UploadJob < Struct.new(:audiofile_id)
  
  
  
        def perform
  
          path = audiofile.wav_file.url.to_s
  
          mp3_file = File.join(Rails.root, "tmp", "uploads", "#{audiofile.filename}.mp3")
  
          %x[ffmpeg -i "#{path}" -b:a 192k -ar 44100 -metadata title="#{audiofile.title}" -metadata artist="#{audiofile.mp3_artist_name}" -metadata album="#{audiofile.mp3_album}" -metadata date="#{audiofile.release_date}" -metadata genre="#{audiofile.genre}" "#{mp3_file}"]
  
          audiofile.mp3_file = open(mp3_file)
  
          audiofile.save!
  
          File.delete(mp3_file)
  
        end
  
  
  
      end

  Note : the wav file comes from a dropbox chooser box.

  My wav job (ran before the mp3 job) :

      class WavUploadJob < Struct.new(:audiofile_id)
  
  
  
        def perform
  
          audiofile.remote_wav_file_url = audiofile.dropbox_wav
  
          audiofile.save!
  
        end
  
      end