Enables or disables read-ahead in a media source.
PROPVARIANT type (vt)
Applications can use this property to configure some media sources. To set the property, pass an IPropertyStore pointer to the source resolver. For more information, see Configuring a Media Source.
If the value is VARIANT_TRUE, the media source will not read ahead in the byte stream. This setting can optimize performance if you plan to read a limited amount of data from the media source—for example, to get a thumbnail image from a video file.
For typical audio/video playback, this property should be set to VARIANT_FALSE. The default value is VARIANT_FALSE.
Not every media source supports this property.