|Microsoft DirectX 9.0|
The UseOverlayStretch method determines whether the renderer should check overlay stretch limitations.
HRESULT UseOverlayStretch( long UseOverlayStretch );
Value specifying whether the renderer checks overlay stretching. Set to OATRUE for the renderer to check overlay stretching; otherwise, set to OAFALSE.
Returns an HRESULT value.
Some display cards provide the use of overlay surfaces through DirectDraw. An overlay surface is a block of video memory whose contents are overlaid onto the display during the monitor's vertical refresh. DirectShow uses all available overlay surfaces where possible because they typically offer higher-quality video and very fast performance. On some display cards set to relatively high bit depths, the overlay must be displayed on the screen larger than its real size (to accommodate certain display hardware bandwidth limitations). If the overlay is not displayed large enough, certain undesirable effects can be seen on the display (sometimes described as a "fleeting shimmering" effect).
If UseOverlayStretch is set to OATRUE (on, the default), DirectShow will ensure the overlay is adequately stretched before displaying it. If it is set to OAFALSE (off), DirectShow will not check that the overlay is adequately stretched, and the user is likely to experience artifacts on the screen (although it will also guarantee that the overlay will be used if possible).