DASH: Support <Label>text</Label> element for adaptation sets

[ssenanayake]

[REQUIRED] Issue description

Currently in Exoplayer "DashManifestParser" the "label" is treated as an attribute in "AdaptationSet". Based on the DASH Spec it's a node of "Label"

[REQUIRED] Reproduction steps

Current Exoplayer DASH parser: https://github.com/google/ExoPlayer/blob/release-v2/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/manifest/DashManifestParser.java Line 275

DASH Spec: https://dashif-documents.azurewebsites.net/DASH-IF-IOP/master/DASH-IF-IOP.pdf

DASH XSD: https://standards.iso.org/ittf/PubliclyAvailableStandards/MPEG-DASH_schema_files/DASH-MPD.xsd

[REQUIRED] Link to test content

N/A - This is to indicate that "label" is not an attribute of "AdaptationSet"

Sample from dashif: https://dash.akamaized.net/dash264/TestCasesIOP41/MultiTrack/alternative_content/6/manifest_alternative_lang.mpd

[REQUIRED] A full bug report captured from the device

N/A

[REQUIRED] Version of ExoPlayer being used

2.10.4

[REQUIRED] Device(s) and version(s) of Android being used

N/A

[ojw28]

If I remember correctly, labels weren't defined anywhere when we added support for them. Support was added by an external contribution: #2904, which turned into #4391.

Do you know where the Label node is defined? It doesn't seem to be defined in the schema you've linked to. The DASH-IF doc you've linked to defines its existence, but not what it is. It's unclear what the actual structure of a Label node is supposed to be. The sample MPD you've linked to doesn't seem to use the Label node for its intended purpose, which is to provide a textual description of the content, and appears to contain redundant information (i.e. lang, which is defined directly on the AdaptationSet). So the sample doesn't really clarify how these nodes are supposed to be defined.

If you could clarify or ask DASH-IF to clarify, that would be great!

[ssenanayake]

Please refer to section 3.9.2 ("Adaptation Set Labeling Options for Selection") of https://dashif.org/docs/DASH-IF-IOP-v4.2-clean.htm#_Toc511040753

"Label | 0 � N | See ISO/IEC 23009-1 [4], clause 5.3.7.2 Table 9. This element enables to provide a textual description of the content. This element should be used if content author expects that clients supports UI for selection. However, this element must not be used as the sole differentiating element as at start-up no user interaction is available."

[ojw28]

ISO/IEC 23009-1 [4], clause 5.3.7.2 Table 9 doesn't define Label though :(. Seems like an error in the DASH-IF document.

[ojw28]

I filed Dash-Industry-Forum/DASH-IF-IOP#383 for clarification.

[ojw28]

Clarification provided on the issue ref'd above. We'll add support for parsing <Label>text</Label. We'll keep support for @label as an attribute as well. If both are present then the former (i.e. standardized) version will win.