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There are many elements in the MPD which have DescriptorType such as Role, Reporting, Scope etc.

A DescriptorType element have three members

@schemeIdUri mandatory
@value optional
@id optional

but is somewhat more complex according to the xsd (ISO/IEC 23009-1 Section 5.8.3).

<!-- Descriptor -->
<xs:complexType name="DescriptorType">
  <xs:sequence>
    <xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
  </xs:sequence>
<xs:attribute name="schemeIdUri" type="xs:anyURI" use="required"/> <xs:attribute name="value" type="xs:string"/>
<xs:attribute name="id" type="xs:string"/>
<xs:anyAttribute namespace="##other" processContents="lax"/>
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</xs:complexType>

However, the code currently defines Descriptor to be a DRM-specific descriptor with Cenc and ppsh entries.
It would be good to rename that to DrmDescriptor or something similar and have a generic Descriptor type that
can be used for other values in the DRM.

There are a few values that can be added for completeness.

1. SegmentTemplate - can be part of AdaptationSet and should be added to the struct.

    <AdaptationSet mimeType="video/mp4" segmentAlignment="true" startWithSAP="1" bitstreamSwitching="false" subsegmentAlignment="true" subsegmentStartsWithSAP="1">
      <SegmentTemplate timescale="90000" duration="180180" startNumber="1"/>

2. Duration - should be added to SegmentTemplate.

Duration. *string `xml:"duration,attr"`

<SegmentTemplate timescale="44100" media="aac_$Number%09d$.mp4" initialization="aacinit.mp4" duration="88288" startNumber="1"/>

3. AudioChannelConfiguration - should be added to Representation.

AudioChannelConfiguration *AudioChannelConfiguration `xml:"AudioChannelConfiguration,omitempty"`

type AudioChannelConfiguration struct {
    SchemeIDURI *string `xml:"schemeIdUri,attr"`
    Value       *string `xml:"value,attr,omitempty"`
}

<Representation id="6" bandwidth="192000" audioSamplingRate="48000" codecs="ec-3">
        <AudioChannelConfiguration schemeIdUri="urn:mpeg:mpegB:cicp:ChannelConfiguration" value="6"/>
</Representation>

This looks like a nice library for manipulating DASH MPDs.

I'm considering using this library for a project similar to https://github.com/dash-Industry-Forum/dash-live-source-simulator in Go, but there are very many MPD nodes and attributes missing before I can use it.

I can make some PRs for the elements I'm missing, but would like to know to understand if you have a strong opinion on how to add optional attributes.

For example, I would like to add contentType to AdaptationSet, and I could either do it as

	ContentType             string           `xml:"contentType,attr,omitempty"`

or

ContentType             *string           `xml:"contentType,attr"`

In my view, the first approach should be more efficient since it avoids one level of pointers, and it is also more clear
(at least to me) that this is an optional attribute. However, I get the impression that you use the pointers like *string to signal that something is optional.

What is your recommendation?

Based on timeline can can you give example to sync segment to wall clock time video and audio both. Dynamic and $number$ based template

The library seems to assume that the DASH file would only have one Period section, whereas it can have multiple, numbered periods.

If interested let me know willing to compensate