Video Disk Control Protocol

VDCP (Video Disk Control Protocol) is a communication protocol primarily used to control hard disk systems dedicated to the recording and playback of video and audio content in the broadcast industry. VDCP was originally developed by Louth Automation and used to be called Louth Protocol.

The video disk communications protocol uses a tightly coupled master-slave methodology. The controlling device takes the initiative in communications between the controlling device (automation) and the controlled device (video disk). The topology is point to point. The videodisk protocol conforms to the OSI (open system interconnection) reference model.

Layer 1, is the physical layer which consists of the electrical and mechanical specifications.

Layer 2, the data link level covers the synchronization and error control for the information transmitted over the physical link.

Layers 3 and 4 provide network functionality and are not applicable.

Layer 5, the session layer, provides the control structure for communications between applications: establishes, manages, and terminates connections (sessions) between cooperating applications.

Layer 6, the presentation layer, contains the control language (dialect).

The commands tables and command description provides this functionality. A time line command set has been included for systems that must use the protocol over a nondeterministic network environment.

Electrical and Mechanical Specifications

1. Communications Signal

a. Asynchronous bit serial, word serial

b. Conforms to EIA RS-422A

c. Full duplex communications channel

d. Transfer rate: 38.4 kb/s.

2. Bit Configuration

a. 1 start bit (space)

b. 8 data bits

c. 1 parity bit (odd)

d. 1 stop bit (mark)

e. Byte time = .286 msec.

3. Connection (9 Pin D-subminiature)

PIN - CONTROLLING DEVICE - CONTROLLED DEVICE

1 - Frame Ground - Frame Ground

2 - Receive A - Transmit A

3 - Transmit B - Receive B

4 - Transmit Common - Receive Common

5 - Spare - Spare

6 - Receive Common - Transmit Common

7 - Receive B - Transmit B

8 - Transmit A - Receive A

9 - Frame Ground - Frame Ground

Information source and detailed protocol document:

http://www.broadcast.harris.com/support/protocols.asp http://www.broadcast.harris.com/support/kb/supportdocs.asp?fid=1250 http://support.omneon.com/Updates/Omneon/Documentation/vdcp.pdf