Building a Multi-Channel PVR System?

Dr.Ruud asks: "What would be good ways to build a multichannel VCR? Think of a cluster of 4 PCs, each having 4 TV-cards (with MPEG-hardware on each) and (if necessary) a separate harddisk per TV-card, and maybe a 5th PC that controls the others, holds a DVD-writer and any other necessary hardware. Could it be done in a simpler and cheaper way? See also linuxtv.org, linuxmedialabs.com and of course SouceForge-vcr-projects like Freevo." What would be the best way to go about cutting down the number of machines such a cluster would need? Could this be done by building an all-in-one-wonderbox without it getting really expensive?

Comments

hmm

[twiggy]

In theory, you'd also need an array of hard drives, because the thrashing of four or more things being recorded at once would be painful...

This would mean you'd have a maximum of 4 hard drives, unless you buy an IDE card that lets you support more, wouldn't it? (Each IDE chain can have only two devices, right? or is that outdated info now?)

An interesting idea for certain though...

Save data before it is decoded

[maddogsparky]

For the amount that you are talking about spending on hardware, you might be able to afford a high-bandwidth A2D converter configured to capture the raw signal (you may have to frequency shift it). Then you can decode it off-line and in slack time when you figure out what you want.

Same idea for for HDTV, except save the data stream.

5 PCs?!?

[nuxx]

I highly doubt you'd need five PCs. What you would need, though, is four MPEG2 hardware capture cards with built-on TV tuners. Remember, a MPEG2 isn't all that big... From rough estimates in my head, any modern DMA100 IDE disk should be able to handle the bandwidth of four MPEG2 streams. You also won't need that powerful of a CPU, either. I'd say that with a little bit of special capture software (that can address four different cards) that will do tuning and scheduling and a TV-out device (Composive, S-Video, and Component) with hardware MPEG2 decoding (or a fairly fast box), you'll have all you need. If they are combination capture / playback cards, you could technically have four outs, too. Might be nice for family time. Queue it up so capture takes priority on all cards but one, or...? The possibilities are endless.

But anyway, I personally would think that you would only need two or MAYBE 3 streams at once, but if you already have software to address more than one card, why stop with just two? As long as the hard drive and PCI bus can handle it, you're set.

Possible Hack

[nukey56]

I recall a conversation I had with the digital cable installer awhile back. He had never heard of PVRs before, and as I was talking about them, he suggested that since the data for all the channels is coming in on the same line at the same time, it could be possible to modify a cable receiver to capture multiple channels at once. This wouldn't solve the problem of how to record them all, though I'm guessing a 8/16/(insert number of channels here) SCSI hard drive setup would work nicely.

I have often thought that BeOS

[teamhasnoi]

would be perfect for such a multitasking box. It's exactly what Beos was designed to do. Multiple video streams would most likely be cake to a low end Beos box.

I talked to some developers over at BeBits about the idea; one said that he had no interest in updating any of his Beos apps and that he had entirely moved over to Windows. (ugh)

The other was intrigued, but had far too much stuff going on already.

Any ideas? Anyone thought this too? I would dive on in, but I am a musician and left programming behind with Apple II basic...

P.S. Trolls: Oh yes, Beos is dead, what am I thinking, I should learn to code, I smell like cats, blahblahblah.

Re:Why not...

[Ssolstice]

Why watch less tv? So he can just put useless posts on Slashdot like yours? The guys asked for technical advice, not for gripes.

Maybe he wants distributed capture

[t0qer]

I've read all the comments about the limitations on the PCI bus, basically there's no way around the lack of bandwidth.

What if he wanted to do distributed capture though?

Think about it, you have 4 machines capturing alternating frames. Machine 1 does frame 1,5,9 machine 2 does 2,6,10, machine 3 does 3,7,11 ect.

This thought occurred to me last night while doing some kazaa downloading. Maybe a better P2p capture system would involve each client downloading 1 frame per movie, and sharing that with the world. The clients could assemble the movie from a distributed network, much like a frame server does in premiere.

The real advantage to doing this would be movies that are stored in a lossless format.