text: Q:
  
  How to create a MPD file of MPEG-DASH to play a webm video?
  
  I'm following this demo which uses mediaSource API and MPEG DASH standard to play a .webm video. 
  This is the MPD file used:
  <?xml version="1.0" encoding="UTF-8"?>
  <MPD
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="urn:mpeg:DASH:schema:MPD:2011"
    xsi:schemaLocation="urn:mpeg:DASH:schema:MPD:2011"
    type="static"
    mediaPresentationDuration="PT888.05S"
    minBufferTime="PT1S"
    profiles="urn:webm:dash:profile:webm-on-demand:2012">
    <Period id="0" start="PT0S" duration="PT888.05S" >
    <AdaptationSet id="0" mimeType="video/webm" codecs="vp8" lang="eng" width="720"      height="306" subsegmentAlignment="true" subsegmentStartsWithSAP="1" bitstreamSwitching="true">
    <Representation id="1" bandwidth="534144">
      <BaseURL>mevq_logo_720x306_0250k_int-150-150.webm</BaseURL>
      <SegmentBase indexRange="29052226-29054708">
        <Initialization range="0-229" />
      </SegmentBase>
    </Representation>
    <Representation id="2" bandwidth="1078766">
      <BaseURL>mevq_logo_720x306_0500k_int-150-150.webm</BaseURL>
      <SegmentBase indexRange="56003676-56006200">
        <Initialization range="0-229" />
      </SegmentBase>
    </Representation>
    <Representation id="3" bandwidth="1745140">
      <BaseURL>mevq_logo_720x306_0750k_int-150-150.webm</BaseURL>
      <SegmentBase indexRange="83686040-83688577">
        <Initialization range="0-229" />
      </SegmentBase>
    </Representation>
    <Representation id="4" bandwidth="2295403">
      <BaseURL>mevq_logo_720x306_1000k_int-150-150.webm</BaseURL>
      <SegmentBase indexRange="111588024-111590567">
        <Initialization range="0-229" />
      </SegmentBase>
    </Representation>
    <Representation id="5" bandwidth="3797938">
      <BaseURL>mevq_logo_720x306_1500k_int-150-150.webm</BaseURL>
      <SegmentBase indexRange="166960740-166963291">
        <Initialization range="0-229" />
      </SegmentBase>
    </Representation>
    <Representation id="6" bandwidth="6418657">
      <BaseURL>mevq_logo_720x306_2000k_int-150-150.webm</BaseURL>
      <SegmentBase indexRange="222165200-222167753">
        <Initialization range="0-229" />
      </SegmentBase>
    </Representation>
  </AdaptationSet>
  <AdaptationSet id="1" mimeType="audio/webm" codecs="vorbis" lang="eng" audioSamplingRate="41000" subsegmentStartsWithSAP="1">
    <Representation id="7" bandwidth="115479">
      <BaseURL>evq_vorbis_128kbps_cues-5sec_tracks-2.webm</BaseURL>
      <SegmentBase indexRange="11944509-11947524">
        <Initialization range="0-4501" />
      </SegmentBase>
    </Representation>
  </AdaptationSet>
  
  Does anybody know how to obtain/calculate the numbers 'SegmentBase indexRange' and 'Initialization range' for any video?
  
  A:
  
  indexRange contains Segment Index Box (sidx).
  It is basically metadata fragment that contains information about the fragments the player should request when downloading the file.
  This is a quote from the spec:
  
  "indexRange specifies the byte range that contains the Segment Index
    in all Media Segments of the Representation. The byte range
    shall be expressed and formatted as a byte-range-spec as defined in
    RFC 2616, Clause 14.35.1. It is restricted to a single expression
    identifying a contiguous range of bytes."
  
  sidx box is described in HERE
  and a parser can be found HERE and HERE(from dash.js project)
  Initialization - According to spec:
  
  "specifies the URL including a possible byte range for the
    Initialization Segment."
  
  Hope it helped!
  
  