CVideoTransformFilter Class

Microsoft DirectShow 9.0

CVideoTransformFilter Class

The CVideoTransformFilter class is designed primarily as a base class for AVI decompressor filters. This class adds support for quality control to the CTransformFilter class. The filter's Receive method can decide to drop frames, based on quality messages from the renderer and performance measurements that the filter collects while it is streaming.

If the filter drops a frame, it continues to drop frames until it reaches the next key frame. For MPEG streams, the filter does not distinguish between B frames and P frames.

Protected Member Variables	Description
m_bQualityChanged	Indicates whether the filter has dropped frames.
m_bSkipping	Indicates whether the filter is currently dropping frames.
m_itrAvgDecode	Average length of time it has taken to decode a frame.
m_itrLate	Indicates how late the samples are arriving at the renderer.
m_nFramesSinceKeyFrame	The number of frames that the filter has received since the last key frame.
m_nKeyFramePeriod	The largest observed interval between key frames.
m_nWaitForKey	The current maximum number of delta frames to drop.
m_tDecodeStart	Length of time that it took to decode the most recent sample.
Protected Methods
AbortPlayback	Used to signal a streaming error.
AlterQuality	Notifies the filter that a quality change is requested.
Receive	Receives a media sample, processes it, and delivers an output sample to the downstream filter.
ShouldSkipFrame	Determines whether the filter should drop a specified sample.
StartStreaming	Called when the filter switches to the paused state.
Public Methods
CVideoTransformFilter	Constructor method.
EndFlush	Ends a flush operation.