Difference between revisions of "Developer:Davaar:InfoService"
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Revision as of 15:18, 18 November 2010
Contents
Architecture Overview
The Info Service provides source-independent information concerning the currently playing media. Introduced in Cara 6, this service should allow a subscribing control point to report on what is currently being played without having to know which source is currently active.
This information is centred around the concept of a Track, which has a Uri and Metadata in DIDL-Lite form.
The Track may also have Details, which describe the bit-rate, sample-rate, bit-depth, etc. These Details may not be known at the point of a track changing. Typically they become known shortly after the track has started playing.
Furthermore, the Track might have Metatext, such as karaoke lyrics or broadcaster information in the case of an internet radio station. This Metatext typically changes as the track is played. Actually, more typically, it is always blank, since since few tracks contain information of this sort.
Counters
Counters are used to manage the changing of the Track, Details, and Metatext information.
When a track changes, the Track Count is incremented, the Uri and Metadata are set, the Details Count is set to zero, the Details are defaulted to blank and zero values, the Metatext Count is set to zero, and the Metatext is set to blank.
Subsequent updates to the Details and Metatext are accompanied by increments in their respective Counters.
The Counters action can be used by clients that are unable to partake in UPnP eventing in order to establish changes in the information provided by the Info Service.
NOTE: The Track Counter should not be confused with the Track Id or Preset Id reported from the Playlist Service or Radio Service. These values are not related.
Track
Reports current Track information:
- Uri
- Metadata
Details
Reports current Details information:
- Duration
- Bit Rate
- Bit Depth
- Sample Rate
- Lossless
- Codec Name
Metatext
Reports dynamic textual information. What this currently amounts to is broadcast information from internet radio stations, but the same mechanism could be used for other purposes in the future.
API Reference
Info Service Description (XML)
Migration Guide
None.
Upnp Action Name Changes
None.
Obsolete Functions
None.
