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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?
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 or is that outdated info now?)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...
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I could maybe understand for archive purposes. As for me, I don't think I've ever had more than 3 things on at any one time that I wanted to watch, and even very seldom more than 1. But a single machine of this hypothetical cluster would do it for me, quite happily.
Do not confuse duty with what other people expect of you; they are utterly different.Duty is a debt you owe to yourself.
While I see the occasional need for 2 tuners, frankly sometimes even that sounds like overkill. I find when there are two shows on at once it's a subtle message from the TV gods that I shouldn't watch so much TV.
I've also never figured out why you need the DVD burner. With so much disk in my Tivo, there is always stuff to watch, and my need for archiving stuff to watch again later is so small as to be unimportant. If I _really_ need it, a lot of it is at the video store for rent.
Is the 16 tuners so you could have a box shared by a whole LAN of people? I guess if you have the bandwidth that would make sense.
Right now the public thinks PVRs are too complex, so the big vendors will probably be working to make them simpler rather than more complex.
What we really need is a component architecture, with lots of little pieces, all with 100mbit ethernet (firewire and USB 2.0 are too "smart" for their own good. ether is the
way to go.)
Then just add what you need. Tuner boxes (OTA, digital or satellite as needed.) Decoders, mounted right on the inputs of the TV that plug in ethernet and spit out component video or NTSC. The ethernet of course leads you to drives running NFS or SMB, and an always on processor to control it all that's simple.
That way you can start simple, with just a tuner, a decoder and a controller (these 3 might be in the same box) and a networked drive or a drive-in-a-box, and add what you want.
Has it been over a year since you last donated to the Electronic Frontier Foundation
Same idea for for HDTV, except save the data stream.
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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.
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 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.
720 horizontal pixels * 480 vertical pixels * 32 bits per pixel * 29.97 frames per second = 331MBytes/second.
32bit, 33MHz PCI is 105MBytes/second. Most PCs have this, which is not capable of even supporting one uncompressed card. Of course, for this reason, TV cards do compression.
DVD quality video is 9 Mbit/sec. Assuming the encoder on the card is not as good, you can get plenty good video at 10-12mbit/sec. And you can fit pretty much as many of those onto a PCI bus as you have slots, I'd think, if the software is decently efficient and supports it. Likewise, this is pretty slow compared to typical disk I/O rates, assuming you do some buffering to allow decent-sized writes to occur and aren't seeking all the time.
Why watch less tv? So he can just put useless posts on Slashdot like yours? The guys asked for technical advice, not for gripes.
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.
What is it with this anti-TV religion that some people seem to have joined? It's not just that they don't watch TV, they insist that nobody else should watch TV either. If you watch TV you're an inferior person! They interrupt conversations to make sure that everybody knows they don't watch TV. They are insanely PROUD of the fact that they have never seen an episode of Farscape, or didn't watch the 6-o-clock news last night.
At what point did "not watching TV" become such a huge achievement for these people? Is there a similar group of anti-readers? Imagine some nutjob interrupting a conversation about an Asimov novel to make it clear that he never reads novels and in fact doesn't even own any novels! You'd rightfully think a person like that was mentally deranged, yet this bizarre behaviour is proudly proclaimed when the medium is television.
To all you idiots repeating the tired mantras of "I never watch TV!" and "You TV watchers should get lives!", I say that you are the people without lives if you think not watching TV is some sort of achievement.