Format.langauge for Arabic tracks return arb instead of ar

[LuGO0]

When filing a question:

This is a sample manifest adaptation set that I am testing, for the English audio adaptation set I get the correct isoCode which is the 2 letters en I expected the same for the Arabic track as well, but it returned 3 letter iso code arb.
Is this expected for the Arabic language? is it IETF BCP 47 conformant or is it a bug?
I am using 2.16.1 as the exoplayer version.

<AdaptationSet mimeType="audio/mp4" startWithSAP="1" segmentAlignment="true" lang="eng" subsegmentAlignment="true" subsegmentStartsWithSAP="1">
    <!-- MPEG Common Encryption -->
    <ContentProtection schemeIdUri="urn:mpeg:dash:mp4protection:2011" value="cenc" cenc:default_KID="39aa2d7b-212e-c6e4-dd26-b6d3deec92a2" />
    <!-- Widevine -->
    <ContentProtection schemeIdUri="urn:uuid:edef8ba9-79d6-4ace-a3c8-27dcd51d21ed">
        <cenc:pssh>AAAALnBzc2gAAAAA7e+LqXnWSs6jyCfc1R0h7QAAAA4IARABGgNoZXMiA2hlcw==</cenc:pssh>
    </ContentProtection>
    <Representation id="audio_aac_1649092788119-en-mp4a-1" codecs="mp4a.40.2" bandwidth="56706" audioSamplingRate="48000">
        <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2" />
        <BaseURL>seg-audio_aac_1649092788119-en-mp4a-1.mp4</BaseURL>
        <SegmentBase indexRange="793-5012">
            <Initialization range="0-792" />
        </SegmentBase>
    </Representation>
    <Representation id="audio_aac_1649092788119-en-mp4a-2" codecs="mp4a.40.2" bandwidth="73134" audioSamplingRate="48000">
        <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2" />
        <BaseURL>seg-audio_aac_1649092788119-en-mp4a-2.mp4</BaseURL>
        <SegmentBase indexRange="793-5012">
            <Initialization range="0-792" />
        </SegmentBase>
    </Representation>
    <Representation id="audio_aac_1649092788119-en-mp4a-3" codecs="mp4a.40.2" bandwidth="137166" audioSamplingRate="48000">
        <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2" />
        <BaseURL>seg-audio_aac_1649092788119-en-mp4a-3.mp4</BaseURL>
        <SegmentBase indexRange="793-5012">
            <Initialization range="0-792" />
        </SegmentBase>
    </Representation>
</AdaptationSet>
<AdaptationSet mimeType="audio/mp4" startWithSAP="1" segmentAlignment="true" lang="arb" subsegmentAlignment="true" subsegmentStartsWithSAP="1">
    <!-- MPEG Common Encryption -->
    <ContentProtection schemeIdUri="urn:mpeg:dash:mp4protection:2011" value="cenc" cenc:default_KID="39aa2d7b-212e-c6e4-dd26-b6d3deec92a2" />
    <!-- Widevine -->
    <ContentProtection schemeIdUri="urn:uuid:edef8ba9-79d6-4ace-a3c8-27dcd51d21ed">
        <cenc:pssh>AAAALnBzc2gAAAAA7e+LqXnWSs6jyCfc1R0h7QAAAA4IARABGgNoZXMiA2hlcw==</cenc:pssh>
    </ContentProtection>
    <Representation id="audio_aac_1649755297605-ar-mp4a-1" codecs="mp4a.40.2" bandwidth="57007" audioSamplingRate="48000">
        <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2" />
        <BaseURL>seg-audio_aac_1649755297605-ar-mp4a-1.mp4</BaseURL>
        <SegmentBase indexRange="793-5012">
            <Initialization range="0-792" />
        </SegmentBase>
    </Representation>
    <Representation id="audio_aac_1649755297605-ar-mp4a-2" codecs="mp4a.40.2" bandwidth="74232" audioSamplingRate="48000">
        <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2" />
        <BaseURL>seg-audio_aac_1649755297605-ar-mp4a-2.mp4</BaseURL>
        <SegmentBase indexRange="793-5012">
            <Initialization range="0-792" />
        </SegmentBase>
    </Representation>
    <Representation id="audio_aac_1649755297605-ar-mp4a-3" codecs="mp4a.40.2" bandwidth="140960" audioSamplingRate="48000">
        <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2" />
        <BaseURL>seg-audio_aac_1649755297605-ar-mp4a-3.mp4</BaseURL>
        <SegmentBase indexRange="793-5012">
            <Initialization range="0-792" />
        </SegmentBase>
    </Representation>
</AdaptationSet>

cc @SaurabhOfficial @vinodkputta

[tonihei]

ExoPlayer doesn't parse the arb language code because it's an individual sublanguage ("Standard Arabic") of the Arabic macrolanguage (which is represented by ar (ISO 639-1) or ara (ISO 639-2)). See https://iso639-3.sil.org/code/ara.

For other macrolanguages, we have a special mapping list to detect individual languages and map them back to their standardized macrolanguage so that they are compatible (e.g. Indonesian, in is mapped to ms-ind as an individual language of the Malay macrolanguage). I guess it makes sense to do the same here and map arb to ar-arb to indicate that we have an Arabic language as the main language and "Standard Arabic" as the individual sublanguage.

If you wonder why we haven't done that already and just map every existing individual code to its macrolanguage - the reason is simply that the list is too long and most of the codes are unlikely to ever appear in a media streaming service (see https://en.wikipedia.org/wiki/ISO_639_macrolanguage for a full list)

[SaurabhOfficial]

Got it @tonihei answers my question. Thanks ✌️

[tonihei]

This is fixed by the commit above.

[SaurabhOfficial]

Thank you !