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• If multiple channels, merge then take sample length from audio file and save it to s3

  18 mai 2017, par khinester

  I am using transloadit to extract the audio from a video file, which is then saved to S3.
  This works great, but I wanted to know how to :

  1. check if the file has multiple channels and then squash it inot one as per https://transloadit.com/demos/audio-encoding/merging-multiple-audio-streams/ - do I need to check for this or do i default to use this robot ?

  2. extract a small sample from the audio file - and save this as a separate file.

  For example, I have a 2h audio file from which I want to take 5% of the length and save this as sample.mp3

  In ffmpeg, i can cut :

  ffmpeg -ss 0 -t 30 -i original.mp3 sample.mp3

  but I am unsure how to chain this workflow, here is what i have thus far :

  const opts = {
  
    params: {
  
      notify_url: `${ process.env.SELF }/services/trans/${ jwToken }`,
  
      steps:      {
  
        import: {
  
          robot:  '/s3/import',
  
          use:    ':original',
  
          bucket: process.env.S3_INGEST,
  
          path:   ingest.key,
  
          key:    process.env.AWS_ID,
  
          secret: process.env.AWS_SECRET,
  
        },
  
        encode: {
  
          robot:        '/audio/encode',
  
          use:          'import',
  
          ffmpeg_stack: 'v2.2.3',
  
          preset:       'aac',
  
          ffmpeg:       {
  
            ab:  '128k',
  
          },
  
        },
  
        export: {
  
          robot:   '/s3/store',
  
          use:     'encode',
  
          bucket:  s3Export,
  
          path:    `${ prefix }/${ token }.m4a`,
  
          headers: {
  
            'Content-Type': 'audio/mp4',
  
            'x-amz-server-side-encryption': 'AES256',
  
          },
  
          key:    process.env.AWS_ID,
  
          secret: process.env.AWS_SECRET,
  
        },
  
      },
  
    },
  
  };

  in the docs, https://transloadit.com/docs/conversion-robots/ i can’t see how to do this ?

  any advice is much appreciated.

• FFmpeg trim .3gp and save as .mp4 not working

  11 avril 2016, par SebSob

  I am trying to trim a video input .3gp (http://www.sample-videos.com/video/3gp/144/big_buck_bunny_144p_2mb.3gp) and save it as .mp4, this is my command :

  ffmpeg -ss 00:00:00.000 -y -i input_vid.3gp -strict experimental -preset ultrafast -t 00:00:03.637 -r 30 -s 176x144 -ar 44100 -b:v 4000k -minrate 4000k -maxrate 4000k -c:a copy -vcodec mpeg4 output_vid.mp4

  But it gives me the following error :

  Setting 'pix_fmts' to value 'yuv420p'
  
  query_formats: 7 queried, 6 merged, 0 already done, 0 delayed
  
  w:176 h:144 fmt:yuv420p sar:12/11 -> w:176 h:144 fmt:yuv420p sar:12/11 flags:0x4
  
  Automatically choosing VBV buffer size of 232 kbyte
  
  intra_quant_bias = 0 inter_quant_bias = -64
  
  Could not find tag for codec amr_nb in stream #1, codec not currently supported in container
  
  Output #0, mp4, to 'output_vid.mp4':
  
    Metadata:
  
      major_brand     : 3gp4
  
      minor_version   : 512
  
      compatible_brands: isomiso23gp4
  
      encoder         : Lavf56.23.100
  
      Stream #0:0(und), 0, 1/15360: Video: mpeg4 ( [0][0][0] / 0x0020), yuv420p, 176x144 [SAR 12:11 DAR 4:3], q=2-31, 4000 kb/s, 30 fps, 15360 tbn, 30 tbc (default)
  
      Metadata:
  
        creation_time   : 1970-01-01 00:00:00
  
        handler_name    : VideoHandler
  
        encoder         : Lavc56.25.100 mpeg4
  
      Stream #0:1(und), 0, 1/8000: Audio: amr_nb (samr / 0x726D6173), 8000 Hz, mono, 12 kb/s (default)
  
      Metadata:
  
        creation_time   : 1970-01-01 00:00:00
  
        handler_name    : SoundHandler
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h263 (native) -> mpeg4 (native))
  
    Stream #0:1 -> #0:1 (copy)
  
  Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument
  
  exit_program: 1 

  But it works fine if the input is an .mp4...

  Any idea’s ? Thanks

• Which Ruby gem should I use to be able to open a video file seek to the keyframes and save them as an image ?

  10 juin 2013, par Konstantin

  I think of some ffmpeg wrapper or libav, which allow to seek to the keyframes relatively fast.