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Digital Video Camcorder Support in Windows 8

RawAVCPkt is an array of eight bytes previously initialized to the required raw AV/C command string except for the track number to search for (bytes 4, 5, and 6).

After GetTransportBasicParameters returns, RawAVCPkt contains any data returned by successful execution of the command.

ulTrackNumToSearch contains the track number specified by the user in the DV Camcorder property page and adjusted for the average time per frame for the device.

LONG cntByte = 8;

BYTE RawAVCPkt[8] = {0x00, 0x20, 0x52, 0x20, 0xff, 0xff, 0xff, 0xff};  

RawAVCPkt[4] = (BYTE)  (ulTrackNumToSearch & 0x000000ff);

RawAVCPkt[5] = (BYTE) ((ulTrackNumToSearch & 0x0000ff00) >> 8);

RawAVCPkt[6] = (BYTE) ((ulTrackNumToSearch & 0x00ff0000) >> 16);

hr =

m_pDVcrExtTransport->GetTransportBasicParameters(

ED_RAW_EXT_DEV_CMD,

&cntByte,

(LPOLESTR *)RawAVCPkt

);

Figure 1 shows the sequence of steps in processing a raw AV/C command. Numbered boxes in the figure are keyed to the text that follows.

Figure 1.  Synchronous Processing of a Raw AV/C Command

During initialization, the COM interfaces acquire a kernel event called UserEvent, which is used to signal completion of a synchronous operation. Only one event is acquired, therefore only one synchronous command can be processed at a time. A DV camcorder driver must support this event for the COM interfaces to send raw AV/C commands to the device.

September 28, 2001

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