23、深入探究媒体会话开发：从拓扑构建到数据处理

深入探究媒体会话开发：从拓扑构建到数据处理

1. 拓扑构建与媒体类型协商

1.1 处理字节流处理程序事件

在媒体会话开发中， CMP3SessionTopoBuilder::HandleByteStreamHandlerEvent() 函数起到关键作用。它首先从字节流处理程序中提取实际的 IMFMediaSource 对象，接着调用辅助函数来协商拓扑中各个组件之间的媒体类型。若一切顺利，该函数会触发 MFSessionTopologyStatus 事件，向播放器表明拓扑已准备好，随后播放器将开始播放。

// make sure that what was created was the media source 
if(objectType != MF_OBJECT_MEDIASOURCE) 
{ 
    hr = E_UNEXPECTED; 
    break; 
} 

// get the IMFMediaSource pointer from the IUnknown we got from EndCreateObject 
m_pSource = pUnkSource; 
BREAK_ON_NULL(m_pSource, E_UNEXPECTED); 

// call a function to negotiate the media types between each MF component in the 
// topology 
hr = NegotiateMediaTypes(); 
BREAK_ON_F