AVCSTRM_OPEN

The AVCSTRM_OPEN function code opens a stream with a specific stream format.

I/O Status Block

If successful, avcstrm.sys sets Irp->IoStatus.Status to STATUS_SUCCESS.

If successful, a STATUS_SUCCESS is returned along with the stream context in AVCStreamContext member of the AVC_STREAM_REQUEST_BLOCK structure. This context is subsequently used for other avcstrm.sys requests.

Possible error return values include:

Error Status	Description
STATUS_DEVICE_REMOVED	The device corresponding to the AVCSTRM_READ operation no longer exists.
STATUS_CANCELLED	The request was unable to be completed.
STATUS_INVALID_PARAMETER	A parameter specified in the IRP is incorrect,
STATUS_INSUFFICIENT_RESOURCES	There were not sufficient system resources to complete the request.
STATUS_PENDING	The request has been received but requires further processing. The I/O completion routine will handle the final response.

AVC_STREAM_REQUEST_BLOCK Input

SizeOfThisBlock, Version and Function
Use the INIT_AVCSTRM_HEADER macro to initialize these members. Pass AVCSTRM_OPEN in the Request argument of the macro.

AVCStreamContext
Specifies the stream context (handle). This should be NULL on input, and if AVCSTRM_OPEN returns successfully, this member contains a valid stream context for subsequent avcstrm.sys operations.

OpenStruct
Specifies the description of the AV/C stream to be created.

The AVCSTRM_FORMAT enumeration provides the list of supported AV/C streaming formats (from the IEC 61883 specifications) that avcstrm.sys supports, such as SDDV (61883-2) and MPEG2TS (61883-4).

In order to make an isochronous connection, the CIP headers and subunit dependent parameters are required and are defined in the AVCSTRM_FORMAT_INFO structure.

The following is an example of the MPEG2TS format information for receiving data:

//
// MPEG2TS
//
    { 
        sizeof(AVCSTRM_FORMAT_INFO),
        AVCSTRM_FORMAT_MPEG2TS,
        {
            0,0,
            CIP_SPH_MPEG, 
            CIP_QPC_MPEG,
            CIP_FN_MPEG,
            IP_DBS_MPEG,
            0,0
        }, // CIP header[0]
        {
            0,0,0,
            CIP_TSF_OFF,
            CIP_FMT_MPEG,
            2,
        },  // CIP header[1]
        SRC_PACKETS_PER_MPEG2TS_FRAME,   // varies depending on number of source packets
        BUFFER_SIZE_MPEG2TS_NO_SPH,   // Remove source packet header
        NUM_OF_XMT_BUFFERS_MPEG2TS,   // Subunit defined
        0,
        FALSE, // not striping SPH is the default
        0,  
        BLOCK_PERIOD_MPEG2TS, // 192, / number of 1394 cycle offset to send one block
        0,0,0,0,
    },

A subunit driver must first allocate an IRP and an AVC_STREAM_REQUEST_BLOCK structure.

Next, it should use the INIT_AVCSTRM_HEADER macro to initialize the AVC_STREAM_REQUEST_BLOCK structure, passing AVCSTRM_OPEN as the Request argument to the macro.

Next, the subunit driver sets the AVCStreamContext member to NULL.

On successful operation, this member should contain a valid stream context (a handle) that is used in subsequent avcstrm.sys operations. This member should not be modified thereafter until the stream is closed through AVCSTRM_CLOSE.. Finally, the subunit driver sets the OpenStruct member of the CommandData union that describes the stream to be opened.

To send this request, a subunit submits an IRP_MJ_INTERNAL_DEVICE_CONTROL IRP with the IoControlCode member of the IRP set to IOCTL_AVCSTRM_CLASS and the Argument1 member of the IRP set to the AVC_STREAM_REQUEST_BLOCK structure that describes the open operation to take place.

A subunit driver can expect this command to complete synchronously. The result returns immediately without pending operation in avcstrm.sys.

This function code must be called at IRQL = PASSIVE_LEVEL.

Comments

This function uses the OpenStruct member of the CommandData union in the AVC_STREAM_REQUEST_BLOCK structure as shown below.

typedef struct _AVC_STREAM_REQUEST_BLOCK {
  ULONG  SizeOfThisBlock;
  ULONG  Version;
  AVCSTRM_FUNCTION  Function;
  .
  .
  PVOID AVCStreamContext;
  .
  .
  union _tagCommandData {
    .
    .
    AVCSTRM_OPEN_STRUCT  OpenStruct;
    .
    .
  } CommandData;
} AVC_STREAM_REQUEST_BLOCK, *PAVC_STREAM_REQUEST_BLOCK;

Requirements

Headers: Declared in avcstrm.h. Include avcstrm.h.

See Also

AVC_STREAM_REQUEST_BLOCK

INIT_AVCSTRM_HEADER

IRP_MJ_INTERNAL_DEVICE_CONTROL

IOCTL_AVCSTRM_CLASS

AVCSTRM_OPEN_STRUCT

AVCSTRM_FUNCTION

AVCSTRM_FORMAT

AVCSTRM_FORMAT_INFO