Question

实时流（MPEG-DASH）提供的MPD文件包含不同的片段开始时间。

我正在流式传输9种3种不同分辨率的流（总共27种流），并且我正在使用Wowza打包程序。

我的MPD文件包含3个适应集，每个适应集都包含一个SegmentTimeline（片段列表）-

第一段具有“ t”（时间）和“ d”（持续时间）。

因此，总共有3个具有“ t”属性的第一段（针对每个适应集）。

其中一个的值不等于另外两个。

这是我的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"
     xmlns:xlink="http://www.w3.org/1999/xlink"
     xsi:schemaLocation="urn:mpeg:DASH:schema:MPD:2011 http://standards.iso.org/ittf/PubliclyAvailableStandards/MPEG-DASH_schema_files/DASH-MPD.xsd"
     profiles="urn:mpeg:dash:profile:isoff-live:2011"
     type="dynamic"
     minimumUpdatePeriod="PT1.489S" 
     publishTime="2019-06-06T12:55:32Z" 
     availabilityStartTime="2019-06-06T12:15:43Z" 
     timeShiftBufferDepth="PT25.0S"
     suggestedPresentationDelay="PT1.0S" 
     minBufferTime="PT6.0S">
<ProgramInformation>
    <Title>camera1.smil</Title>
</ProgramInformation>
<Location>http://...:1935/..../smil:camera1.smil/manifest_w1997958089.mpd</Location>
<Period id="0" start="PT0.0S">
    <AdaptationSet id="0" group="1" mimeType="video/mp4" width="3200" height="640" par="1:1" frameRate="30" segmentAlignment="true" startWithSAP="1" subsegmentAlignment="true" subsegmentStartsWithSAP="1">
        <SegmentTemplate timescale="90000" media="chunk_ctvideo_cfm4s_rid$RepresentationID$_cs$Time$_w1997958089_mpd.m4s" initialization="chunk_ctvideo_cfm4s_rid$RepresentationID$_cinit_w1997958089_mpd.m4s">
            <SegmentTimeline>
                <S t="212758470" d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
            </SegmentTimeline>
        </SegmentTemplate>
        <Representation id="p0va0br3000000" codecs="avc1.640033" sar="1:1" bandwidth="3000000" />
        <Representation id="p0va0br3100000" codecs="avc1.640033" sar="1:1" bandwidth="3100000" />
        <Representation id="p0va0br3500000" codecs="avc1.640033" sar="1:1" bandwidth="3500000" />
        <Representation id="p0va0br4200000" codecs="avc1.640033" sar="1:1" bandwidth="4200000" />
        <Representation id="p0va0br4300000" codecs="avc1.640033" sar="1:1" bandwidth="4300000" />
        <Representation id="p0va0br4150000" codecs="avc1.640033" sar="1:1" bandwidth="4150000" />
        <Representation id="p0va0br3400000" codecs="avc1.640033" sar="1:1" bandwidth="3400000" />
        <Representation id="p0va0br2900000" codecs="avc1.640033" sar="1:1" bandwidth="2900000" />
        <Representation id="p0va0br2800000" codecs="avc1.640033" sar="1:1" bandwidth="2800000" />
    </AdaptationSet>
    <AdaptationSet id="1" group="1" mimeType="video/mp4" width="3200" height="320" par="1:1" frameRate="30" segmentAlignment="true" startWithSAP="1" subsegmentAlignment="true" subsegmentStartsWithSAP="1">
        <SegmentTemplate timescale="90000" media="chunk_ctvideo_cfm4s_rid$RepresentationID$_cs$Time$_w1997958089_mpd.m4s" initialization="chunk_ctvideo_cfm4s_rid$RepresentationID$_cinit_w1997958089_mpd.m4s">
            <SegmentTimeline>
                <S t="212713470" d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
            </SegmentTimeline>
        </SegmentTemplate>
        <Representation id="p0va1br1310000" codecs="avc1.640033" sar="1:1" bandwidth="1310000" />
        <Representation id="p0va1br1320000" codecs="avc1.640033" sar="1:1" bandwidth="1320000" />
        <Representation id="p0va1br1340000" codecs="avc1.640033" sar="1:1" bandwidth="1340000" />
        <Representation id="p0va1br1840000" codecs="avc1.640033" sar="1:1" bandwidth="1840000" />
        <Representation id="p0va1br1850000" codecs="avc1.640033" sar="1:1" bandwidth="1850000" />
        <Representation id="p0va1br1860000" codecs="avc1.640033" sar="1:1" bandwidth="1860000" />
        <Representation id="p0va1br1870000" codecs="avc1.640033" sar="1:1" bandwidth="1870000" />
        <Representation id="p0va1br1380000" codecs="avc1.640033" sar="1:1" bandwidth="1380000" />
        <Representation id="p0va1br1390000" codecs="avc1.640033" sar="1:1" bandwidth="1390000" />
    </AdaptationSet>
    <AdaptationSet id="2" group="1" mimeType="video/mp4" width="3200" height="160" par="1:1" frameRate="30" segmentAlignment="true" startWithSAP="1" subsegmentAlignment="true" subsegmentStartsWithSAP="1">
        <SegmentTemplate timescale="90000" media="chunk_ctvideo_cfm4s_rid$RepresentationID$_cs$Time$_w1997958089_mpd.m4s" initialization="chunk_ctvideo_cfm4s_rid$RepresentationID$_cinit_w1997958089_mpd.m4s">
            <SegmentTimeline>
                <S t="212758470" d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
                <S d="45000"/>
            </SegmentTimeline>
        </SegmentTemplate>
        <Representation id="p0va2br151000" codecs="avc1.640033" sar="1:1" bandwidth="151000" />
        <Representation id="p0va2br252000" codecs="avc1.640033" sar="1:1" bandwidth="252000" />
        <Representation id="p0va2br483000" codecs="avc1.640033" sar="1:1" bandwidth="483000" />
        <Representation id="p0va2br584000" codecs="avc1.640033" sar="1:1" bandwidth="584000" />
        <Representation id="p0va2br585000" codecs="avc1.640033" sar="1:1" bandwidth="585000" />
        <Representation id="p0va2br586000" codecs="avc1.640033" sar="1:1" bandwidth="586000" />
        <Representation id="p0va2br487000" codecs="avc1.640033" sar="1:1" bandwidth="487000" />
        <Representation id="p0va2br258000" codecs="avc1.640033" sar="1:1" bandwidth="258000" />
        <Representation id="p0va2br159000" codecs="avc1.640033" sar="1:1" bandwidth="159000" />
    </AdaptationSet>
</Period>
<UTCTiming schemeIdUri="urn:mpeg:dash:utc:direct:2014" value="2019-06-06T12:55:32Z"/>
</MPD>

您会看到未对齐的位置：

<S t="212758470" d="45000"/>

<S t="212713470" d="45000"/>

<S t="212758470" d="45000"/>

我的问题是：

这是有效的情况吗？
如果是，这种错位的原因是什么？
如果没有，我该如何解决？

请注意，这种错位并非在所有MPD中都发生过，有时甚至会发生。

我的目标是为每个适应集获得完全相同的SegmentTemplate。

Answer 1

实际上，中间适应集（id = 1）比其他两个适应集领先0.5s。值得一提的是，每个片段的持续时间完全等于0.5s。

假设GOP间隔等于0.5s，是什么剥夺了Packager来排列适应集？也许音频流？包括音频吗？如果是这样，我建议禁用音频并重新检查。我还建议询问Wowza专家，如何进行适应性调整。

实时流式MPD包含未对齐段的开始时间

1 个答案: