## 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; // Size of the DDVIDEOPORTBANDWIDTH structure

DWORD dwCaps; // Caps flags

DWORD dwOverlay; // Zoom factor at which overlay is supported

DWORD dwColorkey; // Zoom factor at which overlay w/ colorkey is supported

DWORD dwYInterpolate; // Zoom factor at which overlay w/ Y interpolation is supported

DWORD dwYInterpAndColorkey; // Zoom factor at which overlay w/ Y interpolation and colorkeying is supported

DWORD dwReserved1; // Reserved for future use - set to zero

DWORD dwReserved2; // Reserved for future use - set to zero

} DDVIDEOPORTBANDWIDTH,*LPDDVIDEOPORTBANDWIDTH;

##### Members

dwSize
  Size of this structure, in bytes. This member must be initialized before use.
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 overlay’s minimum stretch factor. 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.
dwYInterpolateAndColorkey
  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 zero.

##### 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 under 1000 mean that the video port is capable of shrinking an overlay when displayed, and values over 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 in order for it to be displayed. In this case, the best possible value is 1000, meaning that no shrinking is required. Smaller values tell you that the source rectangle you specified when calling GetBandwidthInfo were too large and must be smaller. For example, if the stretch factor is 750 and you specified 320 pixels for the dwWidth parameter, then you will not be able to display the overlay at that size. To successfully display the overlay, you must use a source rectangle 240 pixels wide to successfully display the overlay.