DDVIDEOPORTBANDWIDTH

The DDVIDEOPORTBANDWIDTH structure describes the bandwidth characteristics of an overlay surface when used with a particular video-port and pixel-format configuration. This structure is used with the IDirectDrawVideoPort::GetBandwidthInfo method.

typedef struct _DDVIDEOPORTBANDWIDTH {
    DWORD dwSize;          
    DWORD dwCaps;          
    DWORD dwOverlay;       
    DWORD dwColorkey;      
    DWORD dwYInterpolate;  
    DWORD dwYInterpAndColorkey;  
    DWORD dwReserved1;     
    DWORD dwReserved2;     
} DDVIDEOPORTBANDWIDTH,*LPDDVIDEOPORTBANDWIDTH; 

Members

dwSize

Size of this structure, in bytes. This member must be initialized before the structure is used.

dwCaps

Flag values specifying device dependency. This member can be one of the following values:

DDVPBCAPS_DESTINATION

This device's capabilities are described in terms of the minimum stretch factor of the overlay. Bandwidth information provided for this device refers to the destination overlay size.

DDVPBCAPS_SOURCE

This device's capabilities are described in terms of the required source overlay size. Bandwidth information provided for this device refers to the source overlay size.

dwOverlay

Stretch factor or overlay source size at which an overlay is supported, multiplied by 1000. For example 1.3 = 1300, or .75 = 750.

dwColorkey

Stretch factor or overlay source size at which an overlay with color keying is supported, multiplied by 1000. For example 1.3 = 1300, or .75 = 750.

dwYInterpolate

Stretch factor or overlay source size at which an overlay with y-axis interpolation is supported, multiplied by 1000. For example 1.3 = 1300, or .75 = 750.

dwYInterpAndColorkey

Stretch factor or overlay source size at which an overlay with y-axis interpolation and color keying is supported, multiplied by 1000. For example 1.3 = 1300, or .75 = 750.

dwReserved1 and dwReserved2

Reserved; set to 0.

Remarks

When DDVPBCAPS_DESTINATION is specified, the stretch factors described in the other members describe the minimum stretch factor required to display an overlay with the dimensions given when calling the GetBandwidthInfo method. Stretch factor values of less than 1000 mean that the video port is capable of shrinking an overlay when displayed, and values of more than 1000 mean that the overlay must be stretched larger than their source to be displayed.

When DDVPBCAPS_SOURCE is specified, the stretch factors described in the other members describe how much you must shrink the overlay source for it to be displayed. In this case, the best possible value is 1000, meaning that no shrinking is required. Smaller values mean that the source rectangle that you specified when calling GetBandwidthInfo was too large. For example, if the stretch factor is 750 and you specified 320 pixels for the dwWidth parameter, you cannot display the overlay at that size. To display the overlay, you must use a source rectangle 240 pixels wide.

Requirements

  Windows NT/2000: Requires Windows 2000.
  Windows 95/98: Requires Windows 95 or later. Available as a redistributable for Windows 95.
  Header: Declared in dvp.h.