ULONG
VC_GetOverlayMode(
VCUSER_HANDLE vh
);
The VC_GetOverlayMode function requests a kernel-mode video capture driver to return the device’s overlay, color keying, and decompression capabilities.
Parameters
vh
Handle to the kernel-mode driver, obtained from VC_OpenDevice.
Return Value
Returns an unsigned long value containing flags that indicate the types of overlay capabilities supported by the hardware. Zero indicates that overlay is not supported. A nonzero return value can contain the following flags.
| Flag | Definition |
| VCO_KEYCOLOUR | Indicates the device supports a key color. |
| VCO_KEYCOLOUR_FIXED | Indicates the key color cannot be modified. |
| VCO_KEYCOLOUR_RGB | If set, indicates the key color must be specified as an RGB color. If clear, indicates the key color must be specified as a palette index number. |
| VCO_SIMPLE_RECT | Indicates the device supports a single rectangular overlay region. |
| VCO_COMPLEX_REGION | Indicates the device supports a complex (multi-rectangle) overlay region. |
| VCO_CAN_DRAW_Y411 | Indicates the device can display bitmaps that contain YUV 4:1:1-formatted data. |
| VCO_CAN_DRAW_S422 | Indicates the device can display bitmaps that contain YUV 4:2:2-formatted data. |
Comments
The VCO_CAN_DRAW_Y411 and VCO_CAN_DRAW_S422 flags indicate the types of compressed formats the hardware supports for playback by means of the VC_DrawFrame function.
The VC_GetOverlayMode function calls DeviceIoControl (described in the Win32 SDK) to send an IOCTL_VIDC_OVERLAY_MODE control code to the specified kernel-mode driver. When a kernel-mode driver using VCKernel.lib receives this control code, its GetOverlayModeFunc function is called.