PCAM_ALLOCATE_BW_ROUTINE_EX callback function (usbcamdi.h)

Article
02/22/2024

A camera minidriver's CamAllocateBandwidthEx callback function selects the appropriate alternate setting within the USB video streaming interface and prepares the device to stream.

Syntax

PCAM_ALLOCATE_BW_ROUTINE_EX PcamAllocateBwRoutineEx;

NTSTATUS PcamAllocateBwRoutineEx(
  PDEVICE_OBJECT BusDeviceObject,
  PVOID DeviceContext,
  PULONG RawFrameLength,
  PVOID Format,
  ULONG StreamNumber
)
{...}

Parameters

BusDeviceObject

Pointer to the camera minidriver's device object created by the USB hub.

DeviceContext

Pointer to the camera minidriver's device context.

RawFrameLength

Specifies the size, in bytes, of the raw frame data from the packet stream.

Format

Pointer to a KS_DATAFORMAT_VIDEOINFOHEADER structure associated with this stream.

StreamNumber

Specifies the stream number.

Return value

CamAllocateBandwidthEx returns STATUS_SUCCESS or an appropriate error code.

Remarks

USBCAMD calls the camera minidriver's CamAllocateBandwidthEx callback function immediately before the isochronous video capture stream is started. It is called in connection with a Run command.

Typically, this function calls the USBCAMD_SelectAlternateInterface service to select the correct alternate interface and prepare for streaming video.

The original USBCAMD does not call CamAllocateBandwidthEx.

This function is required.

Requirements

Requirement	Value
Target Platform	Desktop
Header	usbcamdi.h (include Usbcamdi.h)