GetVideoPortBandwidth (Windows CE 5.0)
This callback function informs drivers of bandwidth requirements for any specified format. This information can only be given after the video port object is created because the information in the DDVIDEOPORTDESC structure is required before accurate bandwidth information can be supplied. This callback function is required.
DWORD GetVideoPortBandwidth(LPDDHAL_GETVPORTBANDWIDTHDATApgvpbd);
Parameters
- pgvpbd
[in, out] Pointer to a DDHAL_GETVPORTBANDWIDTHDATA structure that contains the information required for the driver to get the bandwidth data.
Return Values
Returns one of the following values:
Remarks
The available bandwidth for some devices depends primarily on the amount of pre-scaling and on the amount that the overlay is zoomed. The available bandwidth for other devices depends primarily on the source size of the overlay. This function supports both types of devices.
If this function is called with the DDVPB_TYPE flag set in the DDHAL_GETVPORTBANDWIDTHDATA structure, the hardware abstraction layer (HAL) should indicate which type of device it is by setting the DDVPBCAPS_SOURCE or DDVPBCAPS_DESTINATION flags in the DDVIDEOPORTBANDWIDTH structure. The DDVPBCAPS_SOURCE size indicates that the bandwidth depends on the overlay source size, and the DDVPBCAPS_DESTINATION size indicates that the bandwidth depends on the overlay destination size.
When this function is called with the DDVPB_VIDEOPORT flag set, the dwWidth and dwHeight members in the DDHAL_GETVPORTBANDWIDTHDATA structure refer to the video port pre-scale parameters. The HAL should return the overlay stretch factors at which it is possible to perform the various levels of support, for example, 1X = 1000, 2X = 2000, and so on. This flag assumes that the device is best described using the DDVPBCAPS_DESTINATION flag. If this is not the case, the HAL should fail the call.
When this function is called with the DDVPB_OVERLAY flag set, the dwWidth and dwHeight members in the DDHAL_GETVPORTBANDWIDTHDATA structure refer to the overlay source size. The HAL should return the percentage of the original overlay size required to perform the various levels of support, for example, none = 1000, 3/4 = 750, and so on. This flag assumes that the device is best described using the DDVPBCAPS_SOURCE flag. If this is not the case, the HAL should fail the call.
Requirements
OS Versions: Windows CE 2.12 and later. Version 2.12 requires DXPAK 1.0 or later.
Header: Ddrawi.h.
Link Library: Developer implemented.
See Also
Video Port Extension Callback Functions | DDHAL_GETVPORTBANDWIDTHDATA | DDVIDEOPORTDESC | DDVIDEOPORTBANDWIDTH | DDHAL_DRIVER_HANDLED | DDHAL_DRIVER_NOTHANDLED
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