Setting the Playback Rate

To change the playback rate, call the IMediaSeeking::SetRate method. Specify the new rate as a fraction of the original rate. For example, to play at twice-normal speed, use the following:

pSeek->SetRate(2.0)

The rate must be greater than zero. Rates greater than one are faster than normal. Rates between zero and one are slower than normal.

Regardless of the playback rate, the current position and the stop position are always expressed relative to the original source. For example, if a source file is 20 seconds long (at normal playback rate), setting the current position to 10 seconds seeks to the middle of the file. If the stop position is 20 seconds (the end of the file) and the playback rate is 2.0, the file will play for another 5 seconds of real time: 10 seconds of source file, at twice the normal playback speed.