如何创建MPEG-DASH的MPD文件来播放webm视频？

Question

我正在关注这个使用mediaSource API和MPEG DASH标准播放.webm视频的演示.这是使用的MPD文件:

<?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>

有谁知道如何获取/计算任何视频的数字'SegmentBase indexRange'和'Initialization range'？

Answer 1

indexRange包含段索引框(sidx).它基本上是元数据片段,包含有关播放器在下载文件时应该请求的片段的信息.这是规范的引用:

"indexRange指定包含表示的所有媒体段中的段索引的字节范围.字节范围应表示并格式化为RFC 2616,条款14.35.1中定义的字节范围规范.它仅限于单个表达式,用于标识连续的字节范围."

SIDX箱中描述该处 和解析器可以发现这里和这里(从dash.js项目)

初始化 - 根据规范:

"指定包含初始化段的可能字节范围的URL."

希望它有所帮助!