Offline rendition management

[defagos]

As a user I would like to be able to control which subtitles, audio tracks and qualities are downloaded so that I can optimize download size and device free space.

Remark

• The system player UI seems to filter out locally unavailable renditions, our Player APIs currently probably don't and will provide all renditions from offline persisted playlists, even if these renditions have not been downloaded.
• We should ensure the player never attempts loading unavailable renditions, otherwise playback will start with a "No network" error. To test:
  • Download a content with only selected subtitles downloaded.
  • Pick subtitles that are not available. If online they will be displayed and content will play just fine.
  • Close the player and disconnect the network. When opening the player previous subtitles will be restored. If not available and incorrectly not filtered, playback fails with a "No network" error.

Acceptance criteria

• An API to select renditions is available.
• Automatic selection is correctly taken into account.
• AD and SDH preferences are correctly taken into account.
• Rendition selection is possible based on media selections and variant qualifiers.
• Renditions can be managed if possible (e.g. later download another rendition, delete a rendition).
• The demo provides a way to customize rendition selection (e.g. global setting or at the time a download is started) or management if possible (e.g. from a dedicated contextual menu).

Tasks

• ...

[defagos]

A very interesting comment from the Apple Developer Forums:

1. AVAssetDownloadConfiguration is capable of specifying multiple quality/bitrate variants. However, with its default settings, AVAssetDownloadTask will download only a single variant, selecting the best quality that is compatible with the device’s capabilities. If multiple variants are desired by the application, AVAssetDownloadConfiguration.auxiliaryContentConfigurations should be configured with the appropriate requirements.
2. The behavior remains consistent regardless of whether the multi-variant playlist offers different resolutions or only differing bitrates.
3. A predicate set through AVAssetDownloadContentConfiguration.variantQualifiers always results in the download of a single video variant. If the predicate yields no matches, the system automatically selects one variant based on the device’s capabilities.
4. Metadata for additional variants may be present in the *.movpkg, but only a single video variant will contain actual media segments unless auxiliaryContentConfigurations is used to explicitly configure multi-variant downloads.