VDCP - Video Disk Control Protocol

With the onset of file based systems I am surprised that I have not been asked before to implement this protocol. A few years ago we added the DD35 protocol to the SR-4 for FranceTelevision to control a EVS Video Server using . We have also implemented some Odetics support. The DD35 and  Odetics protocols  are both of these are extensions to the Sony P2  protocol as is our own xmc protocol used by CBServer. VDCP uses the same RS422 format and speed but has a completely different structure.

I have modified our Sony P2 test software to include the basic VDCP command set and we can now read the file names, select clips and control the transport, the next step will be Synchronisation and Insert Record.

There are still a few commands that I am having trouble with, but the basics are there. The first software will be for the the RM-6 synchroniser, I will then add the protocol to the UR controllers.

When will we implement Ethernet protocols? The problem is that no protocol stands out as a standard. Most are in house protocols which are not published, this makes them difficult if not impossible to implement.

No More Eproms!

The RomUpd card and program are now working very well, and all future SR-4's, RM-6's and dedicated systems  will have it fitted.  This week I was adding a user request to the software and used it for debugging the program. There is nothing like using a program to work out the wrinkles. The installation is also easy as only four connections are made to the processor board with NO track cuts. Just be careful not to lose the screws!

USB-422 Low Latency Driver for Mac

The USB-422 uses the FTDI chipset, this has been very reliable and has the advantage of well supported drivers for Windows, Mac and Linux.

The only drawback of the standard FTDI driver is that it is shipped with a standard latency of 16 mSec which is long for RS422 control, especially at 29.97fps where one frame is only 33 mSec.

The data sheet shipped with the USB-422 includes details of how to reduce the latency and change the com port number for Windows applications, I have just modified this to suggest a latency setting of 1 or 2 mSec and not 4 mSec as before.

Latency adjustment for the Mac is more complicated as the driver must be modified and re-installed. To make this modification easier I have updated the USB-422 web page with a low latency driver and installation instructions.

http://www.colinbroad.com/cbsoft/usb422/usb422.html
  

SR-4/RM-6 Field Programable Update

The SR-4 and RM-6 are both fully supported current products, at one point I was designing replacements but realised that then I would have to support both old and new. I decided to concentrate on supporting the current SR-4 and RM-6. For example they are both now supplied with bi-level and tri-level video sync inputs. The upgrade kit for this is available so that even the oldest of units can be modified.

The SR-4 and hence the RM-6 were designed in the days when EPROMS ruled, all my current products have field programable software and some even have field programable hardware! I finally worked out how add this feature to the SR-4 and RM-6. The new add on board plugs in in place of the EPROM and holds two versions of the software, the programming software (Available for both MAC and Windows)  to reprogram one at any time. The user can then select which version to use, in this way even if the new version is corrupted there is always a working version available.

We will be offering an upgrade kit  and all future units will be shipped with the modification.

Modification instructions will be available on the SR-4 and RM-6 web pages, CB Electronics and selected agents will offer an upgrade service.

Track Arming using Sony P2 Protocol

I am frequently asked "How many tracks is it possible to arm using Sony protocol?"

Using the Sony P2 protocol the maximum tracks that can be armed is 112 calculated as follows
Maximum number of data bytes = 15
One bute is used for analog audio, video and Insert or Assemble
14 bytes may be used for track arming 14*8 = 112

The track arm tally request command includes a byte with a byte specifying offset and length making it is possible to request more track arm tallies but this is not normally used.

Not all manufactures have implemented 112 tracks, within CB the RM-6 and SR-4 support 96 tracks, The UR-422 and UR-422usb support 64 tracks. CBServer currently supports 80 tracks which will soon be increased to 96 tracks. Until recently Pro-Tools supported a maximum of 48 Tracks.


When I originally designed the SR-4 8 or 16 record tracks per machine was standard (DA-88,DD-8...) I provided system track arming to cope with recording onto multiple machines by allowing each record key to be routed to any track on any machine.

With advances in computer hardware it is now common place to have a single record machine with 64 tracks and 96 or more are being discussed.

This question came up recently at Twickenham studios, the AMS-Neve DFC MCS supports a maximum of 48 tracks on each output port, paradoxically the DFC supports 96 track arms internally. To use all 96 tracks it is necessary to use two output ports.

To cope with the limited track arm capability of the DFC output ports CB have written software so that two  DFC-MCS ports are connected to two inputs on the X-4 software. An extra option has been added allowing  the track arming on une input to be offset by 48 tracks.

CBServer with Harrison Console I/F

The Harrison Console uses the same protocol as CBServer (XMC) until now we have only supported both Harrison and CBServer when using an X4 expansion hub. However there are some systems using just a SR-6. This does not allow for the simultaneous connection on the console and CBServer.

The latest software allows Port E and F to be used for CBServer and Harrison.

Note1: Port E must be configured as an input
Note2: The interface is controlled by Port F, if communication to port F is terminated then port E will also terminate!

Timecode Levels

For most of our products the timecode output is designed for the analog world. The level is fixed at 1.2v Peak to Peak with a 40uSec rise time and  rounded corners in order to minimize crosstalk  Recently we have noticed a number on computer based systems that require a higher level on the timecode output. Where I have fitted a gain resistor this is quite easy, just add a suitable resistor, where this is not possible the simplest solution is to double up the diodes as shown in the diagrams below .  

RM-6 Generator Ouput with two extra 1N4146 Didoes Added

TC-5 Timecode output with R10 = 10K for 6dB gain

You can find most circuits at the following url

http://www.colinbroad.com/cbsoft/circuits/circuits.html