title: MPEG-DASH - Multiplexed Representations Issue
body: <p>I'm trying to learn ffmpeg, MP4Box, and MPEG-DASH, but I'm running into an issue with the .mp4 I'm using. I'm using ffmpeg to demux the mp4 with this command:</p>
  
  <pre><code>ffmpeg -i test.mp4 -c:v copy -g 72 -an video.mp4 -c:a copy audio.mp4
  </code></pre>
  
  <p>Once the two files are created, I use MP4Box to segment the files for the dash player using this command:</p>
  
  <pre><code>MP4Box -dash 4000 -frag 1000 -rap -segment-name segment_ output.mp4
  </code></pre>
  
  <p>Which does create all the files I think I need. Then I point the player to the output_dash.mpd and nothing happens except a ton of messages in the console:</p>
  
  <pre><code>[8] EME detected on this user agent! (ProtectionModel_21Jan2015) 
  [11] Playback Initialized 
  [21] [dash.js 2.3.0] MediaPlayer has been initialized 
  [64] Parsing complete: ( xml2json: 3.42ms, objectiron: 2.61ms, total: 0.00603s) 
  [65] Manifest has been refreshed at Wed Apr 12 2017 12:16:52 GMT-0600 (MDT)[1492021012.196]  
  [72] MediaSource attached to element.  Waiting on open... 
  [77] MediaSource is open! 
  [77] Duration successfully set to: 148.34 
  [78] Added 0 inline events 
  [78] No video data. 
  [79] No audio data. 
  [79] No text data. 
  [79] No fragmentedText data. 
  [79] No embeddedText data. 
  [80] Multiplexed representations are intentionally not supported, as they are not compliant with the DASH-AVC/264 guidelines 
  [81] No streams to play.
  </code></pre>
  
  <p>Here is the MP4Box -info on the video I'm using:</p>
  
  <pre><code>* Movie Info *
      Timescale 1000 - Duration 00:02:28.336
      Fragmented File no - 2 track(s)
      File suitable for progressive download (moov before mdat)
      File Brand mp42 - version 512
      Created: GMT Wed Feb  6 06:28:16 2036
  
  File has root IOD (9 bytes)
  Scene PL 0xff - Graphics PL 0xff - OD PL 0xff
  Visual PL: Not part of MPEG-4 Visual profiles (0xfe)
  Audio PL: Not part of MPEG-4 audio profiles (0xfe)
  No streams included in root OD
  
  iTunes Info:
      Name: Rogue One - A Star Wars Story
      Artist: Lucasfilm
      Genre: Trailer
      Created: 2016
      Encoder Software: HandBrake 0.10.2 2015060900
      Cover Art: JPEG File
  
  Track # 1 Info - TrackID 1 - TimeScale 90000 - Duration 00:02:28.335
  Media Info: Language "Undetermined" - Type "vide:avc1" - 3552 samples
  Visual Track layout: x=0 y=0 width=1920 height=816
  MPEG-4 Config: Visual Stream - ObjectTypeIndication 0x21
  AVC/H264 Video - Visual Size 1920 x 816
      AVC Info: 1 SPS - 1 PPS - Profile High @ Level 4.1
      NAL Unit length bits: 32
      Pixel Aspect Ratio 1:1 - Indicated track size 1920 x 816
  Self-synchronized
  
  Track # 2 Info - TrackID 2 - TimeScale 44100 - Duration 00:02:28.305
  Media Info: Language "English" - Type "soun:mp4a" - 6387 samples
  MPEG-4 Config: Audio Stream - ObjectTypeIndication 0x40
  MPEG-4 Audio MPEG-4 Audio AAC LC - 2 Channel(s) - SampleRate 44100
  Synchronized on stream 1
  Alternate Group ID 1
  </code></pre>
  
  <p>I know I need to separate the video and audio and I think that's where my issue is. The command I'm using probably isn't doing the right thing. </p>
  
  <p>Is there a better command to demux my mp4? 
  Is the MP4Box command I'm using best for segmenting the files? 
  If I use different files, will they always need to be demuxed?</p>
  
  <p>One thing to mention, if I use the following commands everything works fine, but there is no audio because of the <code>-an</code> which means it's only video:</p>
  
  <pre><code>ffmpeg -i test.mp4 -c:v copy -g 72 -an output.mp4
  
  MP4Box -dash 4000 -frag 1000 -rap -segment-name segment_ output.mp4
  </code></pre>
  
  <p><strong>UPDATE</strong></p>
  
  <p>I noticed that the video had no audio stream, but the audio had the video stream which is why I got the mux error. I thought that might be an issue so I ran this command to keep the unwanted streams out of the outputs:</p>
  
  <pre><code>ffmpeg -i test.mp4 -c:v copy -g 72 -an video.mp4 -c:a copy -vn audio.mp4
  </code></pre>
  
  <p>then I run:</p>
  
  <pre><code>MP4Box -dash 4000 -frag 1000 -rap -segment-name segment_ video.mp4 audio.mp4
  </code></pre>
  
  <p>now I no longer get the Multiplexed representations are intentionally not supported... message, but now I get:</p>
  
  <pre><code>[122] Video Element Error: MEDIA_ERR_SRC_NOT_SUPPORTED 
  [123] [object MediaError] 
  [125] Schedule controller stopping for audio 
  [126] Caught pending play exception - continuing (NotSupportedError: Failed to load because no supported source was found.)
  </code></pre>
  
  <p>I tried playing the video and audio independently through Chrome and they both work, just not through the dash player. Ugh, this is painful to learn, but I feel like I'm making progress.</p>