PCAM_PROCESS_PACKET_ROUTINE_EX callback function (usbcamdi.h)

Article
02/22/2024

A camera minidriver's CamProcessUSBPacketEx callback function processes a USB packet.

Syntax

PCAM_PROCESS_PACKET_ROUTINE_EX PcamProcessPacketRoutineEx;

ULONG PcamProcessPacketRoutineEx(
  PDEVICE_OBJECT BusDeviceObject,
  PVOID DeviceContext,
  PVOID CurrentFrameContext,
  PUSBD_ISO_PACKET_DESCRIPTOR SyncPacket,
  PVOID SyncBuffer,
  PUSBD_ISO_PACKET_DESCRIPTOR DataPacket,
  PVOID DataBuffer,
  PBOOLEAN FrameComplete,
  PULONG PacketFlag,
  PULONG ValidDataOffset
)
{...}

Parameters

BusDeviceObject

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

DeviceContext

Pointer to the camera minidriver's device context.

CurrentFrameContext

Pointer to the camera minidriver's frame context.

SyncPacket

Pointer to a USBD_ISO_PACKET_DESCRIPTOR structure from the sync pipe. This value is NULL if the interface has only one pipe.

SyncBuffer

Pointer to the data for the SyncPacket.

DataPacket

Specifies the isochronous packet descriptor from data pipe.

DataBuffer

Pointer to DataPacket.

FrameComplete

Pointer to a BOOLEAN value that the camera minidriver sets to indicate whether this is the first data packet for a new video frame.

PacketFlag

Pointer to a value that the minidriver sets to indicate the contents of the current frame. It should be set to one of the following values:

Flag	Meaning
USBCAMD_PROCESSPACKETEX_DropFrame	The current frame is unsalvageable. The read IRP should be recycled.
USBCAMD_PROCESSPACKETEX_NextFrameIsStill	The frame is a still image.
USBCAMD_PROCESSPACKETEX_CurrentFrameIsStill	The current frame is for the still pin.

ValidDataOffset

Pointer to a ULONG value that indicates an offset from the beginning of the packet. USBCAMD should start the copy from this offset. This eliminates the extra buffer copy in the case of an in-band signal. If the camera is not using in-band signaling, ValidDataOffset should be set to zero.

Return value

This function returns the number of bytes that should be copied.

Remarks

The minidriver should complete its CamProcessUSBPacketEx function as quickly as possible. Image processing should be deferred to the CamProcessRawVideoFrameEx function.

This callback function is used with isochronous pipes only (video or still streaming).

The original USBCAMD does not call CamProcessUSBPacketEx.

This function is optional.

Requirements

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