Audio track and subtitle analytics

[defagos]

As an ADI analyst I want to be able to know whether audio tracks or subtitles have been enabled or not, and which ones.

Acceptance criteria

• Track-related fields are properly sent in Commanders Act streaming analytics.

Tasks

• Discuss forced subtitles. Should we send the subtitle language? (likely not since there is no involved user selection)
• Discuss automatic selection. Should we send the subtitle language? (likely yes since there is a selection involved) If yes then add a method to get the low-level selection, e.g. activeMediaOption(for:).
• Send media_audio_track in Commanders Act analytics (UND if none).
• Send media_subtitle_selection and media_subtitles_on in Commander Act analytics (UND if none).
• Ensure forced subtitles are not sent.

[defagos]

We asked ADI for information, most notably regarding forced subtitles.

[defagos]

I updated our common documentation issue with answers from ADI regarding subtitles. Also check this comment for optionality.

[defagos]

The specifications we have implemented are a best effort, as they were during the Letterbox area. We namely never notify audio or subtitle selection changes, each event merely reflects the current value when it is sent.

With Pillarbox asynchronously responding to changes the play event is recorded before selections are applied, thus subtitles will not be seen as enabled in initial play events, most notably. This status is updated in subsequent events like pos, though, thus this should be acceptable.

If this proves to be an issue in the future:

• Maybe the specifications should be improved (e.g. a dedicated event should be sent).
• Or our tracker implementation should combine playback state, seeking state as well as media selection availability somehow.