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• How to map inputs from multiple device into single stream with multiple channels ?

  30 septembre 2019, par ศาสะ ศรีศักดิ์

  I’m try to use ffmpeg to map audio streams from 4 sound cards in to single file with 8 channels. I’m try to learn how to use map_channel or -filter_complex but no luck, its hard to understand. Please tell me how command should be.

  Here is my code so far.

  ffmpeg -f dshow -i audio="Mic/Inst/Line In 1/2 (4- Studio 1824)"
  
  -f dshow -i audio="Mic/Line In 3/4 (4- Studio 1824)"
  
  -f dshow -i audio="Mic/Line In 5/6 (4- Studio 1824)"
  
  -f dshow -i audio="Mic/Line In 7/8 (4- Studio 1824)"
  
  -filter_complex "[0:a:0][0:a:1][1:a:0][1:a:1][2:a:0][2:a:1][3:a:0][3:a:1] amerge=inputs=8" output.wav

  After many trials and errors. some working code.

  ffmpeg -f dshow -i audio="Mic/Inst/Line In 1/2 (4- Studio 1824)"
  
  -f dshow -i audio="Mic/Line In 3/4 (4- Studio 1824)"
  
  -f dshow -i audio="Mic/Line In 5/6 (4- Studio 1824)"
  
  -f dshow -i audio="Mic/Line In 7/8 (4- Studio 1824)"
  
  -filter_complex "[0:a][1:a][2:a][3:a]amerge=inputs=4[a]" -map "[a]" output.wav

  Thought, I still don’t understand what is -map "[a]" do.

• Can I detect duplicated videos using ffmpeg ?

  28 décembre 2020, par Tobias

  Is it possible to detect duplicate videos (.mp4 files) using ffmpeg (or similar tools) ?

  


  There are around 3000 videos in my file system, some of them twice (since these are automatically downloaded by a bot from various sources). So it can happen that these differ a little from the video / audio quality.

  


  My first idea now would be to render the videos to a quality that is consistent and store the MD5 hash of the file in the database. There I would check for duplicate hashes.

  


  Is this the right approach or does anyone have an idea how I could best implement this ?

  


• Can't preserve metadata in ffmpeg video conversion

  30 avril 2017, par sakovias

  I would like to preserve the creation time metadata when I convert videos using ffmpeg/avconv. Here is the file I’m trying to convert :

  $ ffmpeg -i in.avi 
  
  ffmpeg version 0.8.6-4:0.8.6-0ubuntu0.12.04.1, Copyright (c) 2000-2013 the Libav developers
  
    built on Apr  2 2013 17:00:59 with gcc 4.6.3
  
  Input #0, avi, from 'in.avi':
  
    Metadata:
  
      creation_time   : 2013-08-12 06:59:14
  
      encoder         : CanonMVI06
  
    Duration: 00:00:12.26, start: 0.000000, bitrate: 14549 kb/s
  
      Stream #0.0: Video: mjpeg, yuvj422p, 640x480, 30 tbr, 30 tbn, 30 tbc
  
      Stream #0.1: Audio: pcm_u8, 11024 Hz, 1 channels, u8, 88 kb/s

  In the first approach I run

  $ ffmpeg -i in.avi -vcodec libx264 -acodec libmp3lame -r 30 -map_metadata 0 out.avi

  and get an output file which doesn’t have the ’creation_date’ metadata that I’d like to keep :

  $ ffmpeg -i out.avi 
  
  ffmpeg version 0.8.6-4:0.8.6-0ubuntu0.12.04.1, Copyright (c) 2000-2013 the Libav developers
  
    built on Apr  2 2013 17:00:59 with gcc 4.6.3
  
  [avi @ 0x83ba260] max_analyze_duration reached
  
  Input #0, avi, from 'out.avi':
  
    Metadata:
  
      encoder         : Lavf53.21.1
  
    Duration: 00:00:12.38, start: 0.000000, bitrate: 704 kb/s
  
      Stream #0.0: Video: h264 (Main), yuv420p, 640x480, 30 fps, 30 tbr, 30 tbn, 60 tbc
  
      Stream #0.1: Audio: mp3, 11025 Hz, mono, s16, 200 kb/s

  I also tried another approach

  $ ffmpeg -i in.avi -f ffmetadata metadata.txt
  
  $ ffmpeg -i in.avi -f ffmetadata -i metadata.txt -vcodec libx264 -acodec libmp3lame -r 30 out.avi

  with the same success even though metadata.txt has the right info :

  ;FFMETADATA1
  
  creation_time=2013-08-12 06:59:14
  
  encoder=CanonMVI06

  What am I doing wrong ?