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Multimedia: Audio Management
Functional Description


Media Latency Constraints

Certain audio effects are required to have very low latency. Acceptable latencies are:

Use Case Requirement
Listen to Music Start within 2 seconds
Watch a video Start within 3 seconds, audio synchronized with video to within 50ms
Phone Rings Must start within 1 second of incoming call. Must stop within 300ms of user answering call
Screen click Within 50ms
Key click Within 50ms

Policy Management

Many embedded devices provide "hardwired" audio paths for various audio use cases. Typical use cases are:

A flexible model for modeling hardware audio device topology is provided. The state of the audio system can be queried and modified. The audio state model is generally well-suited to hardware assisted audio paths (for example, when on a phone call, no software intervention is required to route audio data from the microphone to the GSM modem). However, software audio paths are also possible, (e.g. software intervention might be required to play sound to a Bluetooth headset). This framework also provides audio policy management by prioritizing audio profiles. E.g. ring tones and phone call modes take precedence over multimedia playback, etc.

The system is generally independent of the multimedia engine being used, although the use of software based audio routing might require specific implementation(s) for a given multimedia engine (e.g. Helix.)

Sound Priority Levels

Audio Management framework allows multiple audio playback domains, each with an associated priority level. The configuration and priority levels are obtained from a platform specific audio configuration plugin. This allows the system integrator to specify audio priorities, e.g. Multimedia, RingTone, PhoneCall & Alarm. Alarm would have a higher priority than Multimedia but lower than RingTone.

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