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• Single Manifest file for different audio and video segments created using MP4Box (MPEG DASH)

  29 avril 2016, par user3753682

  I have three questions

  1) Does dash.js support audio and video content multiplexed in a single segment ?

  2) If not how to merge audio.mpd and video.mpd created using MP4Box into a single out.mpd, that is supported by dash.js player ?

  3) It works if AdaptationSet is copied manually from audio.mpd and placed in video.mpd and video.mpd is played using dash.js. How to automate it ?

  MP4Box -dash 4000 -frag 4000 -rap -bs-switching no -profile dashavc264:live -segment-name ./video/segment_ -out video.mpd video.mp4#video
  
  
  
  MP4Box -dash 4000 -frag 4000 -rap -bs-switching no -profile dashavc264:live -segment-name ./audio/segment_ -out audio.mpd video.mp4#audio 

• using ffmpeg to create a wavefile image from opus

  29 décembre 2015, par edwardsmarkf

  I have been trying to use ffmpeg to create a wavefile image from an opus file. so far i have found three different methods but cannot seem to determine which one is the best.

  The end result is hopefully to have a sound-wave that is only approx. 55px in height. The image will become part of a css background-image.

  Adapted from Generating a waveform using ffmpeg :

  ffmpeg -i file.opus -filter_complex
  "showwavespic,colorbalance=bs=0.5:gm=0.3:bh=-0.5,drawbox=x=(iw-w)/2:y=(ih-h)/2:w=iw:h=1:color=black@0.5"
  file.png

  which produces this image :
  

  Next, I found this one (and my favorite because of the simplicity) :

  ffmpeg -i test.opus -lavfi showwavespic=split_channels=1:s=1024x800 test.png

  And here is what that one looks like :

  

  Finally, this one from FFmpeg Wiki : Waveform, but it seems less efficient using a second utility (gnuplot) rather than just ffmpeg :

  ffmpeg -i file.opus -ac 1 -filter:a
  aresample=4000 -map 0:a -c:a pcm_s16le -f data - | \
  gnuplot -e "set
  terminal png size 525,050 ;set output
  ’file.png’ ;unset key ;unset tics ;unset border ; set
  lmargin 0 ;set rmargin 0 ;set tmargin 0 ;set bmargin 0 ; plot ’

  

  Option two is my favorite, but i dont like the margins on the top and bottom of the waveforms.

  Option three (using gnuplot) makes the best ’shaped’ image for our needs, since the initial spike in sound seems to make the rest almost too small to use (lines tend to almost disappear) when the image is sized at only 50 pixels high.

  Any suggestions how might best approach this ? I really understand very little about any of the options I see, except of course for the size. Note too i have 10’s of thousands to process, so naturally i want to make a wise choice at the very beginning.

• FFMPEG segment stream into MP4 chunks of 4 seconds [AV out of sync]

  18 décembre 2015, par Kr0e

  I want to segment an incoming RTMP stream into MP4 chunks of 4 seconds.
  These MP4 chunks contain both, audio and video tracks.

  Unfortunately, the duration of the audio and video track are not equal, which leads to AV out-of-sync when playing both tracks at the same time in HTML 5 MSE source buffers.

  mp4info outputs :

  Track 1:
  
    flags:        3 ENABLED IN-MOVIE
  
    id:           1
  
    type:         Video
  
    duration: 4000 ms
  
  
  
  Track 2:
  
    flags:        3 ENABLED IN-MOVIE
  
    id:           2
  
    type:         Audio
  
    duration: 3994 ms

  So, obviously, the audio system does not care about video keyframes.

  How can I fix this ?

  Btw. :

  This is my only issue, MP4 fragmentation is solved using mp4box.js.

  AV out-of-sync is my end boss =]

  Command :

  let camera2TS = spawn('./ffmpeg/darwin/ffmpeg', [
  
        '-rtmp_listen', '1', '-i', 'rtmp://127.0.0.1:1935/foxnet/live',
  
        '-c:v', 'libx264', '-x264-params', 'keyint=240:no-scenecut=1', '-pix_fmt', 'yuv420p',
  
        '-force_key_frames', 'expr:gte(t,n_forced*4)', '-frag_duration', '4',
  
        '-preset', 'ultrafast', '-profile:v', 'baseline', '-level:v', '3', '-r', '25', '-g', '100',
  
        '-strict', 'experimental', '-b:v', '3500k', '-bufsize', '3500k',
  
        '-c:a', 'aac', '-af', 'aresample=async=1',
  
        '-f', 'segment', '-segment_time', '4', '-reset_timestamps', '1',
  
        'chunks/%01d.mp4'
  
      ]);