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September 8, 2004

Medusa PVR

A PC PVR with six tuners
Powered by SnapStream Beyond TV 3.5


We built Medusa here at SnapStream to show off the new multi-tuner capabilities of Beyond TV 3.5.  Yes, it's true: some TiVo's and other PVRs let you record two shows at the same time. But how about turning up the volume on that idea?  How about recording SIX of your favorite shows at the same time?  Well, that's what we set off to create using off-the-shelf computer parts and Beyond TV 3.5.

Table of Contents:




Chassis: Whitebox PC
CPU: 2.4ghz Pentium 4
RAM: 512mb (PC2700)
Hard Disk: 40gb Maxtor (5400rpm)
Capture Cards: Hauppauge PVR-250BTV (aka Hauppauge "Roslyn" board) (x 6)


OS: Windows XP Home
Beyond TV 3.5 (comes with the ability to use 2 tuners)
Beyond TV Tuner Add-on Pack (x 4)
Optional: Beyond TV Link

Hardware Installation:

Installing six tuner cards is no different that installing just one. For Medusa, we started by loading the PVR-250BTV Drivers according to the provided documentation, powering down the machine, and installing each card into its PCI Slot. After tightening all of the screws and plugging the power cord back in, we booted the machine back to Windows XP. Once logged in, we confirmed each of the 30 (yes thirty) driver installation prompts. Once we got through the prompts, all six cards were successfully up and running.





Beyond TV 3.5 Setup:

Beyond TV 3.5 is as easy as getting the hardware up and running. We started by running the Beyond TV 3.5 setup wizard just like normal. Then, we ran through the video source setup for each card. After each card was configured, we had 6 sources setup. For the uber-technical user, the WebUI could also be used to setup the devices.




TV Source:

For the purpose of this test, we wired each TV tuner card to our local Time Warner Cable feed (but we could have had each one connected to a different line-up -- ie one to antenna, one to digital cable, one to a DirecTV satellite, etc.)




Medusa In Use

Once we had the software configured, all that was left was to schedule enough programs to take advantage of all of the tuners. Turns out, it's not that easy to find 6 things on at once that you really want to record, although, there's nothing wrong with an episode of Saved By The Bell every now and then.

Beyond TV Link provides a good opportunity to use all of Medusa's recording power. With Beyond TV Link, while you record two shows at once, four people at different places in the house could be watching (and pausing, rewinding, etc) their own live TV stream. Pretty cool if you've got a lot of people that want to watch TV at the same time.

The best part of using Hardware Encoders (like the PVR-250BTV) is that they don't tax the host CPU. Here, the 6 recordings are taking a total cpu usage of 22%.



Technical considerations

Note: non-nerds can safely skip this section.

Hard Drives:

By this point, you might be wondering what special tricks it took us to turn this mild mannered White Box PC into a Lean Mean Recording Machine. The surpising answer is: It didn't. We used all of the defaults as configured by the setup wizard, including using the "Better" capture resolution. This machine utilizies a 5400rpm, ATA-100, 40gb hard drive. We decided on this drive to prove the point that it doesn't take an insane set of hardware to setup a great recording machine. Notably, this hard drive was getting near its limits for throughput, but it worked just fine given the settings we had chosen.

But what if you wanted to record each show at 12mbps or add more tuners? In that case, you could take a couple of different routes. The cheapest and easiest way would to invest in a larger 7200rpm SATA-150 drive. Barring that, you could also use a striped raid set to increase total disk throughput.

Tuner Cards:

Why did we choose to make Medusa a six tuner system and not add more? Simply put, we ran out of PCI Slots. In theory, we could have used external USB encoders as well, but it was nice to have such a clean installation of the PCI Cards.

Heat Considerations:

Given that each tuner card has an encode processor onboard, adding 6 to a system does slightly raise the internal temperature of the machine. We suggest making sure your machine has proper airflow before attempting this type of setup.

Signal Strength:

At SnapStream, we have a moderatly large signal amp and set of large splitters.
At your house, you may run into issues of signal strenght as you split past the 4th or 5th device. If you run into strength problems, you might consider adding a small signal amp. Radio Shack sell as small one for around $50.





So we agree that not everyone needs a PVR with six TV tuners -- not unless you have a big family and watch a lot of TV or if you live in a fraternity/sorority house -- but Medusa gives you an idea of the possibilities with SnapStream's Beyond TV 3.5. Beyond TV 3.5 delivers a big punch! Be sure and check it out (and if you're a programmer type, don't forget to come back and check out the new Beyond TV SDK when we publish it).

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