OIPF 规范翻译（DAE）-----4.4.5 Media control

翻译于 2010-05-15 16:54:00 发布 · 982 阅读

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#resources #object #application #instantiation #audio #video

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本文详细介绍了在音视频应用中如何管理稀缺资源，如媒体解码器，并阐述了不同请求之间的冲突处理机制。当应用程序对有限的媒体解码资源提出相互冲突的请求时，最近的请求将被优先考虑，而失去资源的对象会生成错误并返回到未实现状态。此外，还讨论了在资源丢失导致错误发生时，如何释放其他已占用的稀缺资源。

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4.4.5 Media control
Instantiation of a video/broadcast or A/V Control object does not cause any scarce resources to be claimed. Scarce
resources such as a media decoder are only claimed following a call to the setChannel(), nextChannel() or
prevChannel() methods on a video/broadcast object or the play() method on an A/V Control object. By
implication, instantiating a video/broadcast or A/V Control object does not cause the media referred to by the
object’s data attribute to start playing immediately. See section 7.13.1.1 for details of when scarce resources are released by a video/broadcast object and section 7.14.1.1 when scarce resources are released by an A/V Control object. Where applications make conflicting requests for limited media decoding resources, the media decoding resources that are requested most recently are presumed to be the ones that are most wanted and the resources SHOULD be granted to the application that most recently requested them regardless of the priority of the application indicated in application signalling. Any objects which have lost the resources shall generate an error (e.g. error code 11 in the case of the video/broadcast object, or error code 3 in the case of the A/V Control object) and, in the case of the video/broadcast object, return to the unrealised state. This applies to conflicts between different requests for
streaming video or audio (whether over RF tuners or IP streams). When an error occurs due to scarce resources being removed from an object, the object SHALL free any other scarce resources that may be held. Multiple applications from the same author which are running simultaneously should co-ordinate their use of scarce resources. This specification is intentionally silent about handling of resource use by embedded applications including scheduled
recordings. If audio from memory interrupts any other media presentation then the interrupted presentation SHALL be restored automatically by the OITF when the interrupting presentation ends. When audio from memory is interrupted by a resource loss, or when streaming video or audio presentation is interrupted by a resource loss caused by another request for streaming audio or video presentation, the presentation is cancelled and
SHALL NOT be restored automatically by the OITF.