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• dash.js : four channels audio streaming

  19 juillet 2016, par Carlos Chacon

  Does dash.js supports 4 channels in the audio stream ?

  I’m using mp4 container : video : h254 and audio : AAC.

  For the case that the AAC audio stream is 2 channels it works fine, both video and audio play correctly. But 4 channels does NOT work.

  I’m using FFMPEG to create the files and WOWZA to setup the DASH streaming.

  For the case that the AAC audio stream is 4 channels I get the following error :

   Video can't be played because the file is corrupt.

  Command line to generate the 2-channels file :

  ffmpeg -i video_in.mp4 -i audio_in_4ch.wav -c:v copy -c:a aac -ac 2 output_2channels.mp4

  Command line to generate the 4-channels file :

  ffmpeg -i video_in.mp4 -i audio_in_4ch.wav -c:v copy -c:a aac -ac 4 output_4channels.mp4

  This is the fmmpeg -i information printed for each file :

  2 Channels output file details :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output_2channels.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.37.101
  
    Duration: 00:00:17.59, start: 0.000000, bitrate: 901 kb/s
  
      Stream #0:0(eng): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 1024x512 [SAR 1:1 DAR 2:1], 894 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 129 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler

  4 Channels output file details :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output_4channels.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.37.101
  
    Duration: 00:00:17.59, start: 0.000000, bitrate: 1038 kb/s
  
      Stream #0:0(eng): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 1024x512 [SAR 1:1 DAR 2:1], 894 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 4.0, fltp, 265 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler

  4 Channels output file mdp file :

  <?xml version="1.0" encoding="UTF-8"?>
  
  <mpd xmlns="urn:mpeg:dash:schema:mpd:2011" profiles="urn:mpeg:dash:profile:isoff-live:2011" type="static" publishtime="2016-07-19T05:56:28Z" mediapresentationduration="PT17.585S" minbuffertime="PT1.5S">
  
  <programinformation>
  
      
  
  </programinformation>
  
  <location>http://192.168.0.103:1935/vod/_definst_/mp4:output_4channels.mp4/manifest_w882219731.mpd</location>
  
  <period start="PT0.0S">
  
      <baseurl>http://192.168.0.103:1935/vod/_definst_/mp4:output_4channels.mp4/</baseurl>
  
      <adaptationset mimetype="video/mp4" width="1024" height="512" par="1024:512" framerate="30000/1001" segmentalignment="true" startwithsap="1" subsegmentalignment="true" subsegmentstartswithsap="1">
  
          <segmenttemplate presentationtimeoffset="0" timescale="90000" media="chunk_ctvideo_rid$RepresentationID$_cs$Time$_w882219731_mpd.m4s" initialization="chunk_ctvideo_rid$RepresentationID$_cinit_w882219731_mpd.m4s">
  
              <segmenttimeline>
  
                  <s t="0" d="1582650"></s>
  
              </segmenttimeline>
  
          </segmenttemplate>
  
          <representation codecs="avc1.42c01e" sar="1:1" bandwidth="894760"></representation>
  
      </adaptationset>
  
      <adaptationset mimetype="audio/mp4" lang="eng" segmentalignment="true" startwithsap="1" subsegmentalignment="true" subsegmentstartswithsap="1">
  
          <audiochannelconfiguration schemeiduri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2"></audiochannelconfiguration>
  
          <segmenttemplate presentationtimeoffset="0" timescale="48000" media="chunk_ctaudio_rid$RepresentationID$_cs$Time$_w882219731_mpd.m4s" initialization="chunk_ctaudio_rid$RepresentationID$_cinit_w882219731_mpd.m4s">
  
              <segmenttimeline>
  
                  <s t="0" d="844080"></s>
  
              </segmenttimeline>
  
          </segmenttemplate>
  
          <representation codecs="mp4a.40.2" audiosamplingrate="48000" bandwidth="265851">
  
          </representation>
  
      </adaptationset>
  
  </period>
  
  </mpd>

  HTML Player Code :

  <code class="echappe-js">&lt;script src=&quot;http://cdn.dashjs.org/latest/dash.all.min.js&quot;&gt;&lt;/script&gt;
  
         
  
  

• Avoiding ffmpeg audio drift for live dash output

  22 mai 2021, par mdale

  Have people experienced playback drift with ffmpeg based dash segment generation ? For example :

  


  ffmpeg -threads 2 -re -fflags +genpts -stream_loop -1 -i AVSyncTest.mp4 \
-af "aresample=async=1:min_hard_comp=0.100000:first_pts=0" \
-c:v:0 libx264 \
-pix_fmt:0 yuv420p \
-preset:0 medium \
-a53cc:0 1 \
-nal-hrd:0 cbr \
-x264opts:0 scenecut=-1:rc_lookahead=0 -b:v:0 5000k -bufsize:0 500k \
-force_key_frames:0 "expr:gte(t,n_forced*2)" \
-bf:0 8 \
-r 30 \
-c:a:0 aac  -ar 48000 \
-b:a:1 96k  \
-f tee -map 0:v \
-map 0:a "[f=dash:media_seg_name='chunk-stream_\$RepresentationID\$-\$Number%05d\$.mp4':init_seg_name='init-stream_\$RepresentationID\$.mp4':seg_duration=2:utc_timing_url=https\\\://time.akamai.com\\?iso:remove_at_exit=0:use_timeline=0:http_user_agent=ffmpeg_encoder.0:streaming=1:index_correction=1:timeout=1:dash_segment_type=mp4:method=PUT:http_persistent=1:adaptation_sets='id=0,streams=v\:0 id=1,streams=a' ]http://localhost:5000/out.mpd "


  


  After a bit of playback it starts audio starts to drift. Analysis of the moof (with tools like mp4box) shows 1024 sample size with 93 Moofs with Moof->traf->default_sample_duration=1024 at 48000 sample rate giving segment duration of 1.984 seconds with every 3rd segment or so with 92 Moofs with duration of 1.962 … While each segment starts aligned ( if you reset playback you get alignment) it drifts against continuous playback.

  


  Other examples like Akamai’s public stream. show 94 Moofs or 2.005 duration with every 3rd segment or so at the 1.984 duration. (what one would want)

  


  Akamai’s (presumably ffmepg based) stream is averaging out to the 2s target where the above ffmpeg command is not …

  


• ffmpeg DASH - Include the stream's width and height (WxH) in the outputted filenames

  20 juillet 2022, par Jarad

  Given this :

  


  ffmpeg -i test.mp4 -c:a aac -c:v libx264 ^
-map v:0 -s:0 960x540 -b:v:0 800k ^
-map v:0 -s:1 320x170 -b:v:0 300k ^
-map 0:a ^
-f dash dash/master.mpd


  


  Produces this :

  


  chunk-stream0-00001.m4s
chunk-stream0-00002.m4s
...
chunk-stream0-00044.m4s
chunk-stream0-00045.m4s
chunk-stream1-00001.m4s
chunk-stream1-00002.m4s
...
chunk-stream1-00044.m4s
chunk-stream1-00045.m4s
chunk-stream2-00001.m4s
chunk-stream2-00002.m4s
...
chunk-stream2-00074.m4s
chunk-stream2-00075.m4s
init-stream0.m4s
init-stream1.m4s
init-stream2.m4s
master.mpd


  


  Inspection shows : ffprobe master.mpd

  


  Input #0, dash, from 'master.mpd':
  Duration: 00:06:11.00, start: -0.021333, bitrate: 0 kb/s
  Program 0
  Stream #0:0: Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 960x540 [SAR 1:1 DAR 16:9], 152 kb/s, 30 fps, 30 tbr, 15360 tbn (default)
    Metadata:
      variant_bitrate : 300000
      id              : 0
  Stream #0:1: Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 320x170 [SAR 17:18 DAR 16:9], 21 kb/s, 30 fps, 30 tbr, 15360 tbn (default)
    Metadata:
      variant_bitrate : 28227
      id              : 1
  Stream #0:2(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 110 kb/s (default)
    Metadata:
      variant_bitrate : 128000
      id              : 2


  


  I want output instead like this :

  


  chunk-stream0-960x540-00001.m4s
chunk-stream0-960x540-00002.m4s
...
chunk-stream0-960x540-00044.m4s
chunk-stream0-960x540-00045.m4s
chunk-stream1-320x170-00001.m4s
chunk-stream1-320x170-00002.m4s
...
chunk-stream1-320x170-00044.m4s
chunk-stream1-320x170-00045.m4s
chunk-stream2-???????-00001.m4s
chunk-stream2-???????-00002.m4s
...
chunk-stream2-???????-00074.m4s
chunk-stream2-???????-00075.m4s
init-stream0-960x540.m4s
init-stream1-320x170.m4s
init-stream2-???????.m4s
master.mpd


  


  where ??????? could be just audio or 48000hz or whatever.

  


  The Question

  


  Is there a way to include the stream's width and height (its size) in the outputted filenames from the command-line interface ? If no, how could it be accomplished using a shell script for example.