source filter 添加 CSourceSeek 接口

原创于 2012-10-31 14:27:22 发布 · 1.2k 阅读

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本文概述了应用程序通过调用FilterGraphManager上的IMediaSeeking方法来查找过滤器图的流程。此过程涉及从FilterGraphManager将请求分布到图中的每个渲染器，并沿上游链路逐个传递给上游过滤器，直至找到可以执行搜索命令的过滤器，通常是源过滤器或解析过滤器。

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Overview of Seeking in DirectShow

An application seeks the filter graph by calling an IMediaSeeking method on the Filter Graph Manager. The Filter Graph Manager then distributes the call to every renderer in the graph. Each renderer sends the call upstream, through the output pin of the next upstream filter. The call travels upstream until it reaches a filter that can execute the seek command, typically a source filter or a parser filter. In general, the filter that originates the time stamps also handles seeking.

A filter responds to a seek command as follows:

The filter flushes the graph. This clears any stale data from graph, which improves responsiveness. Otherwise, samples that were buffered prior to the seek command might get delivered.
The filter calls IPin::NewSegment to inform downstream filters of the new stop time, start time, and playback rate.
The filter then sets the discontinuity flag on the first sample after the seek command.

Time stamps start from zero after any seek command (including rate changes).

转自：http://msdn.microsoft.com/en-us/library/dd758085%28v=vs.85%29.aspx