GetMaxIdealImageSize method retrieves the maximum ideal image size.
HRESULT GetMaxIdealImageSize( long *pWidth, long *pHeight );
Pointer to the maximum ideal width, in pixels.
Pointer to the maximum ideal height, in pixels.
Returns an HRESULT value.
Various renderers have performance restrictions on the size of images they can display. Although they should still function properly when requested to display images larger than the specified maximum, renderers can nominate the minimum and maximum ideal sizes through the IVideoWindow interface. This interface can be called only when the filter graph is paused or running, because it is not until then that resources are allocated and the renderer can recognize its restrictions. If no restrictions exist, the renderer fills in the pWidth and pHeight parameters with the native video dimensions and returns S_FALSE. If restrictions do exist, the restricted width and height are entered, and the member function returns S_OK.
The dimensions apply to the size of the destination video and not to the overall window size. So, when calculating the size of the window to set, account for the current window styles (for example, WS_CAPTION and WS_BORDER).