xml – 如何创建MPEG-DASH的MPD文件来播放webm视频？

发布时间：2020-12-16 23:50:11 所属栏目：百科来源：网络整理

导读：我正在关注这个使用mediaSource API和MPEG DASH标准播放.webm视频的 demo. 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:schemaLocatio

我正在关注这个使用mediaSource API和MPEG DASH标准播放.webm视频的 demo.
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’？

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 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框在HERE中描述
并且可以在HERE和HERE(from dash.js project)找到解析器

初始化 – 根据规范：

“specifies the URL including a possible byte range for the
Initialization Segment.”

希望它有所帮助！

（编辑：李大同）

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