Jun 152010

Some folks on the Left Coast called a couple days back… They were in preproduction for a show which included a GrandMA lighting console and a V1X2 DDR from Doremi Labs.

The V1X2 is a super-sexy disc-based 2-channel HD Video Recorder which (fortunately!) can be controlled through an RS-422 serial bus. The command protocol is an extension of Sony’s 9-pin machine control language.

Their goal was to for the MA system to trigger transport control and random video clip access from the DDR.

Clear back when Sony wrote the protocol, there wasn’t any equipment which supported discrete track playback. Of course, the old tape machines could jam to SMPTE time code, shuttling back and forth as needed. However, ability to load random digital audio and video tracks didn’t exist.

Over time, several companies wrote extensions to the Sony protocol, which allowed digital files with arbitrary names to be cued, played and recorded.

A brief conversation with one of the friendly tech support guys at Doremi uncovered the magic document – a list of the supported serial command used for transport control and discrete track access.

A few hours later, we had working firmware written for the DecaBox protocol bridge. Their GrandMA can now effortlessly control the DDR system.

We ended up with a firmware build which requires six consecutive DMX channels.

The system’s start address can be set using pushbuttons and the LCD. Assuming a base address of 1,

CH 1 @ FF = Stop
CH 2 @ FF = Play
CH 3 @ FF = Record
CH 4 @ FF = FFD
CH 5 @ FF = Jog

CH6 @ 0 = None
CH6 @ [1-4] = Play clip 001
CH6 @ [5-9] = Play clip 002
CH6 @ [10-14] = Play clip 003
CH6 @ [15-19] = Play clip 004


Note that the DMX values will range from [0 255] over the range of 0% – 100%.  This gives access to about 25 discrete clips.

From the lead technician on the project:

I needed a specialty box to convert DMX commands to RS232 and these guys nailed it for me.

John Chapman was prompt, professional and did exactly what he promised to do. The design of the box is rugged and very well put together and was delivered on time.

I would highly recommend Engineering Solutions for any of your control related needs.

David Huseonica

Videocam, Inc.


Thanks, David, for taking a moment to call. We’re always thrilled to help.

 Posted by at 3:22 pm

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