I try to write a USB camera filter driver, and i can print debug stream comming from webcam info. but i can not access data buffer of this stream, following is my code:

I handle RP_MJ_DEVICE_CONTROL to trap stream comming from webcam

NTSTATUS DispatchAny(IN PDEVICE_OBJECT fido, IN PIRP Irp)
PDEVICE_EXTENSION pdx = (PDEVICE_EXTENSION) fido->DeviceExtension;
PIO_STACK_LOCATION stack = IoGetCurrentIrpStackLocation(Irp);
UCHAR type = stack->MajorFunction;
// Pass request down without additional processing
if(type == IRP_MJ_DEVICE_CONTROL)
{
NTSTATUS status = STATUS_SUCCESS;
IoCopyCurrentIrpStackLocationToNext(Irp);
IoSetCompletionRoutine(Irp, SFDDeviceIoCompletion, NULL, TRUE, TRUE, TRUE );
status=IoCallDriver(pdx->LowerDeviceObject,Irp);
return status;
}
else
{
NTSTATUS status;
status = IoAcquireRemoveLock(&pdx->RemoveLock, Irp);
if (!NT_SUCCESS(status))
return CompleteRequest(Irp, status, 0);
IoSkipCurrentIrpStackLocation(Irp);
status = IoCallDriver(pdx->LowerDeviceObject, Irp);
IoReleaseRemoveLock(&pdx->RemoveLock, Irp);
return status;
}
}

I implement a complete function to handle 2 main IRP : IOCTL_KS_READ_STREAM and IOCTL_KS_WRITE_STREAM when next low level driver has completed the requested operation

NTSTATUS SFDDeviceIoCompletion(PDEVICE_OBJECT fido, PIRP Irp, PVOID Context)
{

if(Irp->PendingReturned)
IoMarkIrpPending(Irp);

NTSTATUS status = STATUS_SUCCESS;
PIO_STACK_LOCATION stack = IoGetCurrentIrpStackLocation(Irp);

switch(IoControlCode)
{
case IOCTL_KS_READ_STREAM:

if(Irp->AssociatedIrp.SystemBuffer)
{
KSSTREAM_HEADER *_StreamHeader;
ULONG _BufferSize = 0;
_StreamHeader = (KSSTREAM_HEADER*)Irp->AssociatedIrp.SystemBuffer;
_BufferSize = _StreamHeader->DataUsed;
KdPrint(("device buffer size 2 %d\n", _BufferSize));

if(_BufferSize > 0)
{

PVOID sysBuf = ExAllocatePool(NonPagedPool, _BufferSize);
if(sysBuf)
{
if(_StreamHeader->Data)
{
KdPrint(("Start copy memory"));
RtlCopyMemory(sysBuf, _StreamHeader->Data, _BufferSize);
KdPrint(("Stop copy memory"));
}

ExFreePool(sysBuf);
}

}
}
else if(Irp->MdlAddress)
{
ULONG deviceBufferSize = 0;
deviceBufferSize = MmGetMdlByteCount(Irp->MdlAddress);
KdPrint(("device buffer size 1 %d\n", deviceBufferSize));
}
break;

case IOCTL_KS_WRITE_STREAM:
KdPrint((DRIVERNAME " - IOCTL_KS_WRITE_STREAM\n"));
break;

default:
break;

}
return status;
}

#1
_BufferSize = _StreamHeader->DataUsed;
KdPrint(("device buffer size 2 %d\n", _BufferSize));
I can see at debug view correct size stream, ex: 320 x 240 x 3 (RGB24) or: YUV12

#2
KdPrint(("Start copy memory"));
RtlCopyMemory(sysBuf, _StreamHeader->Data, _BufferSize);
KdPrint(("Stop copy memory"));

When run to this code system die cause by crash error:
*** ERROR: Module load completed but symbols could not be loaded for usbVM31b.sys
Probably caused by : usbcamerafilter.sys ( usbcamerafilter!SFDDeviceIoCompletion+10b

I do not know why i can not access this buffer, can anybody expert about USB Camera Filter Driver help me explain why?

My References: http://www.calsoftlabs.com/whitepape...driver.html#05

Thanks very much.

David.

"David" <thuong101277@yahoo.com> wrote:
You need to show us more of the !analyze -v. What was the blue screen
code? Are you absolutely sure the crash happens in RtlCopyMemory? Did you
print the Data address to make sure it made sense?
--
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

Thank you, i will try to print it.

"Tim Roberts" <timr@probo.com> wrote in message
news:6vvp34lcodoqklo5asctinvn0s2gdc1uu3@4ax.com...

"David" <thuong101277@yahoo.com> wrote:
This code is very different from the code you originally posted. This code
is copying the data directly from the output buffer of the IRP. That's not
how the IRP_KS_READ_STREAM ioctl works.

Which one are you actually running?
--
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

Thank you for reply

Sorry for that, as my originally posted then i can not access buffer webcam
from Irp->AssociatedIrp.SystemBuffer so i try to get form Irp->MdlAddress,
now it work ok.

Now i meet problem listener event open, close stream of webcam from filter
and how to get with, high, bitrate of buffer data, such as see from
reference: http://www.calsoftlabs.com/whitepape...driver.html#05, I need
implemented : IOCTL_KS_PROPERTY handle to trap above informations, it is
correct?

"Tim Roberts" <timr@probo.com> wrote in message
news:kj3344131gefgl844oa2u7voe8uqhekh9d@4ax.com...

"David" <thuong101277@yahoo.com> wrote:
Yes.
--
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

Thank you for reply

Have any articels guide to implement it, or any example how to implement it?
Can you help me?


"Tim Roberts" <timr@probo.com> wrote in message
news:jof944h7qgmr0pmoclketiunufetjst7l1@4ax.com...

"David" <thuong101277@yahoo.com> wrote:
No, but filter drivers are not hard to write, especially if you use KMDF.

What have you tried?
--
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.