| TSReader |
DTVWorks DVB-SPI Interface |
Introduction
The DTVWorks DVB-SPI Interface is a low-cost USB 2 connection between commercial MPEG-2 equipment and our TSReader MPEG-2 transport stream analyzer. DVB-SPI uses a 25-pin d-sub connector just like the connector for a parallel printer port, but unlike printer ports, DVB-SPI uses low-voltage differential signaling (LVDS) which allows data rates of up-to 108 Mbps on short twisted-pair cables.
We designed the interface to be as small as possible with the intent that its connected directly to the back of the SPI-compatible equipment. A USB cable can then easily be routed to get the transport stream into the PC.
The DVB-SPI interface sells for $399 US each, shipping included. Up to eight DVB-SPI interfaces can be connected to a single PC and all can be run simultaneously with TSReader Professional.
Why not DVB-ASI?
When we built a set of prototype boards and made them available to testers, the question we were asked most was "Why not a DVB-ASI interface?". There are really two answers to this question. First, cost: the extra components required to interface to DVB-ASI would have pushed the cost of the interface up much higher. Second, many pieces of commercial gear have both DVB-ASI and DVB-SPI. The ASI is often used to feed other equipment and the SPI port goes unused. With our design based around the 25-pin connector that DVB-SPI uses, you can plug the interface directly into the SPI port and then just run a USB cable to a nearby PC.
Why so inexpensive? What's the catch?
That was the second most asked question! There are many other fine DVB-SPI to USB 2 interfaces available, many of which are supported by TSReader, but almost all of them contain a large buffer to prevent high-rate MPEG-2 transport streams from overrunning the USB bus.
You probably already know that USB 2 operates at 480 Mbps, however, there is overhead in the protocol, so the most that can be achieved is probably closer to 180 Mbps on a single device. Additionally, the design of the USB bus means that the PC is constantly asking the DVB-SPI interface if there is data available to transfer.
Should the PC get slowed down by running CPU intensive applications where the CPU load gets to 100%, there's a possibility that the USB device won't get polled frequently enough and this will cause packet loss. So other manufacturers get around this by putting a large buffer (a FIFO - First-In, First-Out) into their designs which brings up cost and complexity considerably.
Our interface uses only a small FIFO inside the USB 2 interface chip. This buffer is plenty big enough provided the CPU load on the PC stays below 100%, but if the CPU is maxed-out, there is a good possibility of packet loss that wouldn't show up on other DVB-SPI interfaces. That said, we've had the DVB-SPI interface running with TSReader processing transport streams above 65 Mbps without any packet loss.
In other words, don't use this interface for conformance monitoring! But if you've got a rack of equipment with a bunch of empty DVB-SPI ports, connect up each of these interfaces, run the USB cables into a nearby PC, load a remote control client and with the right firewall settings you can see the transport from each device in the rack from anywhere in the world.
What's in the box?
Just the DVB-SPI interface! We don't provide a USB cable -- most people have them lying around and if not, they're very easy to obtain almost anywhere in the world. We feel that if we provided a cable, it would always be the wrong length! The DVB-SPI interface gets its power from the PC so there's no need for separate power supply.
You don't need a driver disc for the DVB-SPI interface either - the driver is already provided with TSReader in the TSReader/Drivers/DTVWorks folder. The source module is also supplied - launch TSReader with the Ctrl key down and choose the DTVWorks_SPI.dll source module from the list or setup a profile for the device in TSReader Professional.
Terms, Conditions, Warranty and Purchase
The interface comes with a 14 day, no questions asked, money back guarantee less shipping of course. If the interface doesn't work with your DVB-SPI gear, just send it back. If you have any doubts about the compatibility of our interface and your gear please tell us the equipment you're using before ordering in case we've already discovered an issue with the interface and that gear.
Should the interface fail within 90 days as a result of a defect in the interface, we'll replace/repair it at no cost excluding shipping.
Shipping and Handling is included in the price which covers UPS Ground to locations in the United States. If you're outside the USA we deliver via United States Postal Service Global Priority Mail. Both offer a delivery within six days. Currently, faster shipping options aren't available.
What about other parallel MPEG-2 interfaces?
Officially the board only supports LVDS signaling, but we've written a short page on our experiments with disabling the LVDS receiver chips and connecting the interface to the insides of some gear that doesn't have a DVB-SPI option, but has parallel TTL MPEG-2 internally. Obviously, adding wires and cutting traces voids the warranty!
What about capturing a stream in my own application?
We have a sample Win32 C++ application with source code available here. It shows how to communicate with the DVB-SPI interface and receive data using the Cypress USB Developer's uStudio - available free from their website. If you're not using Win32, we have documentation that explains how the USB interface's end-points operate. This document is available here.