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Building a Multi-Channel PVR System? 344

Posted by Cliff
from the it-doesn't-HAVE-to-be-a-single-box dept.
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?
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Building a Multi-Channel PVR System?

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  • Eh? (Score:4, Insightful)

    by Masami Eiri (617825) <brain.wav@gmailGINSBERG.com minus poet> on Wednesday January 22, 2003 @05:37PM (#5138835) Journal
    I'm just trying to figure out why you would need 16 programs taping at one time... I am the only one who finds that a bit off the wall?
    • Re:Eh? (Score:3, Interesting)

      by pythorlh (236755)
      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.
    • by minitrue (213792) on Wednesday January 22, 2003 @06:28PM (#5139273)
      This is perfect for public access television stations. They often have 5-10 people, all needing to encode their videotapes at the same time. A multichannel encoder would be heaven!

      I've been working with MNN [mnn.org], the public access station in New York, NY in building a cheap, open source video server out of an old TiVo [mit.edu]. The equipment necessary to program and run television broadcast/cablecast centers is often expensive and proprietary. And unless you do web playback like indymedia [indymedia.org] or freespeechtv [fstv.org], you have to buy the equipment to play the game.

      An open, Linux-based multi-encoder like this (accompanied by an open video server) would do wonders for the community media world!
    • Retro surfing!!! (Score:2, Insightful)

      by jerroldr (247140)
      You would want 16 channels recording at the same time so you could retro surf ....

      So as you surf around and you see something you like, you could rewind to the begining of the show.

      I have Tivo now, and often I will turn on the tv and realize that the show that is currently on, is one that I wish I had seen from the beginning. Since my Tivo was on that station, I can rewind a half hour back in to the buffer, but when I change the channel each channel doesn't have a buffer, so I'm for those I am out of luck. 16 tuners all being recorded would fix that problem ... at least for the stations that are being recorded.
    • by IcEMaN252 (579647) on Wednesday January 22, 2003 @06:48PM (#5139479) Homepage
      ... I work in public access television. I can see several uses for a cheap way to log multiple programs at once.

      • Non-Linear Editing
        If you want to edit video on a computer, you need to "digitize" or "capture" it to the computer. Hook up multiple VTRs and capture multiple tapes at once. There are systems that exist to do this, but they are high dollar. This might not be cheep, but I'm sure there would be some free clock cycles to use.
      • Record Multiple Live Programs
        Say you do a political talk show. You want to do all the research you can. The major networks all have good political shows on Sunday morning. With this you could record them all and watch them later. Yes you could just use VCRs, but that applys to ALL PVR applications.
      • Log Programming on Multiple Stations
        Many public access stations are actually multiple channels. PEG (Public, Educational, and Government) is the standard for Local Access pretty much. You could record the station live from the past so many days and stream it online to catch recent programming.
      • Archiving
        Say you have a large tape archive (the station I work at has beein archiving for under a month and has over 300 tapes) and want to store in a digital media. You could use the captured video either to make DVDs or store in low-res on a server for preview. With IDE RAIDs becoming less and less expensive, a terrabyte fileserver is now an option in the four figures.

      And thats just what I can think of off the top of my head...
    • Re:Eh? (Score:5, Informative)

      by dbrutus (71639) on Wednesday January 22, 2003 @06:49PM (#5139485) Homepage
      Perhaps you're monitoring to see whether your commercial actually airs on the 10-20 channels you bought for your ad campaign. Maybe you work for a non-profit media watchdog group that monitors bias. Maybe you just want to beat the smug smile off the face of your neighbors who claim techno superiority with their Tivo.

      There, three reasons, at least one of which will appeal to most people.
  • hmm (Score:4, Interesting)

    by twiggy (104320) on Wednesday January 22, 2003 @05:38PM (#5138841) Homepage
    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...
    • by maddogsparky (202296) on Wednesday January 22, 2003 @05:43PM (#5138880)
      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.

    • Re:hmm (Score:3, Interesting)

      by Wesley Felter (138342)
      I think you could record quite a few channels to a single disk if you use good enough scheduling. Let's conservatively assume that each stream is 8Mbps (1MB/s), the disk can write 20MB/s, and every seek costs 20ms. If you have a 1-second buffer for each channel, then writing that buffer takes 20+(1000*(1/20)) = 70ms. Thus you can write 14 streams to one disk.
    • by dbrutus (71639)
      Then again, if you were running Firewire, you can have 60+ devices on the chain. Splurge and spend the extra 30 bucks for an IEEE-1394 card.
  • 16-channels at once? (Score:3, Interesting)

    by Anonvmous Coward (589068) on Wednesday January 22, 2003 @05:39PM (#5138853)
    Well, I gotta admit, I'm baffled as to why one would want to record 16 channels at the same time. Why is that interesting to you? What's your goal here? Are you providing a service for somebody? Is this something you'd just like to do at home? Answer that for me and I might be of more assistance.

    Personally, I can't help but think that 4 cards capturing at ideal quality would saturate the PCI bus unless each card directly controlled a hard drive.
    • by goatasaur (604450) on Wednesday January 22, 2003 @05:48PM (#5138937) Journal
      An explanation:

      Basic digital cable provides different premium services... there are 6 HBO channels, 4 Cinemax channels, 4 Showtime channels, and a couple of 24-hour pr0n channels.

      Obviously, the poster's intent was to record more porn. This drive for increased pornography consumption has inspired such innovations as the light bulb (for reading porn), the telephone (for listening to porn), and of course the cotton gin (for making more tube socks).
    • by mlyle (148697)
      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.
      • "720 horizontal pixels * 480 vertical pixels * 32 bits per pixel * 29.97 frames per second = 331MBytes/second."

        Where do you get 32 bits from? Heh. Best I've ever seen is 24, but you could easily drop that to 16 and nobody'd ever know better.

        Other than that, you're right. Personally, though, I'm not a fan of MPEG2. Besides finding a player for it, it's not as efficient as say MPEG 4. I'd prefer to have the CPU do the compression in real time. One of these days I want to put together a dual-processor PVR just to do that. (The other processor is for viewing the footage on my TV without interrupting capture...)
      • You didn't carry your units through. If you multiply out your numbers you end up with 331 mbits/s, which is ~40 mbytes/sec. You also don't really lose anything by recording 480x480 given the crappy quality of most broadcast signals, which would move things down to ~26mbytes/s. (Also if you think my $30 ati tv wonder ve is doing compression I have a bridge for sale...)
        • Not to mention that he's grossly overestimating the colorspace. TVs don't include alpha channels, you can throw 8 bits/pixel out the window right there. Additionally, NTSC doesn't use the RGB color model - it uses YCrCv, which equates to something like RGB with 219 possible values per channel. It all works out to considerably less than 40MB/sec.
    • by mckwant (65143)
      I played with this idea briefly. Imagine a high end hotel offering "whatever" on demand for sum of cash $x. Networking to the rooms is a solved problem (see spectravision, etc.). Only question is how to get the content.

      Well, that, and selling and servicing it in a scalable fashion to hotels that aren't terribly interested in giving you much of a cut.

      Not a bad idea, but you run into trouble with the marketing and the amount of time you need to keep things vs. your affordable drive space. Not to mention the copyright issues the networks will come up with.
  • by mbourgon (186257) on Wednesday January 22, 2003 @05:42PM (#5138874) Homepage
    Version .8 will allow you to have several machines, each taping its own channel(s), controlled by any of the machines in the network. The goal is to allow you to have one gigantic server in the basement, and 1 fan-less machine in the living room.

    Far more interesting is what ramifications (if any) are there to having 2/3/4 tuner cards in one PC. After all, each tuner card probably needs its own sound card... what else is involved?
    • It's a lot easier just to get BT8x8 TV tuners with audio chips supported by the BTAUDIO module - makes a /dev/dspX for each one and you can go from there.
  • Why do you want it (Score:4, Interesting)

    by btempleton (149110) on Wednesday January 22, 2003 @05:43PM (#5138875) Homepage
    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.
    • by Lechter (205925) on Wednesday January 22, 2003 @06:09PM (#5139095)

      A couple thoughts off the top of my head:

      • you want multiple people to be able to use the same cable connection
      • everyone in your house wants a PVR but you don't want to duplicate it in every room
      • you need to record multiple shows on at a given time for analysis (Comm doctoral students do this all the time)
      • you own a TV store and want to stream programming to multiple show pieces
      • you just want to be that damn 1337

      Really folks, when someone asks a question they don't want to be told why they don't need to know the answer. So, come on, don't send off-topic replys about how pathetic or dumb a question is post a constructive answer!

      • by btempleton (149110)
        Everybody seemed to have the same question. If that's the case, you should explain the reason because it will help people come up with an answer.

        In this case, of course you are going to have to do custom work because so few people would seem to need it. I could I could imagine a campus dorm, but even then 16 tuners would be too many.

        (One reason for that is that so many of the shows you watch these days are repeated many times. Since with a PVR you don't care when you watch, many 'conflicts' aren't really conflicts, though the software could be better about this.
        In fact, only the major networks seem not to repeat a lot.)

        Now a more interesting project would be to build a receiver that could record all the closed captioning from all the channels. While you could do that with tons of tuner cards, it seems that there should be an easier way to do it since all you really want is that low bitrate VBR.

        I wonder if you could do something with GNU Radio to get those VBR data streams from multiple channels at once? With enough CPU you could use GNU Radio or other software radio to do the multiple channel recording too.
    • by Anonymous Coward
      I disagree with this. 16 is a bit high, but I understand the problem. When I got a PC PVR, I ran into problems. The problem is pretty simple. For like 18 hours of the day, I don't want to watch or record anything. Maybe a show or two, like Lexx at 2pm. Or something on Toonami.

      But certain days on primetime, there's like 7 shows I'd like to get a handle on to watch later, e.g. a slow weekend, the other hours of the day. Primetime plus ratings seasons equals a LOT of overlap of shows I'd to catch when *I* have the time.

      For example, I liked watching Monster Garage, Mon 8pm on Discovery. But there was, for a time, Lofts on HDTV from 8-8:30. And I think Courage was on a 8pm for a while there. If you were a Third Watch person, as I was for a bit, that was on at 8pm for a while there.

      Or Jag on CBS and Buffy on UPN, Tuesdays at 8.

      Yes, a lot of TV if you're going to sit there and watch it that week. But given how TV runs, there is a lot of crap time, starting first with the other 18 hours of the day, and rerun season is pretty boring. Maybe I want to watch TV when I want to, not when the networks want me to.

      I've only got extended cable. If you have HBO and some premium channels, there's potentially more.

      Yes, the vast majority of stuff on TV is crap. But there is stuff on that's enjoyable. I use a PVR to REDUCE the amount of time I spend in front of the TV channel surfing, waiting for the show to come on, keeping track of what show switched to what time slot (SciFi bastards) or cancelled (Fox bastards).
    • my need for archiving stuff to watch again later is so small as to be unimportant

      Some people feel some sense of accomplishment by owning huge archives of "stuff". For exmaple, we probably all know people that brag about having a 100GB of music files (MP3/Ogg). But when the majority of that collection is crap they don't even like, you've got wonder, what's the point?
      • The Tivo and similar boxes really change that. There is _always_ something decent on the box. I just find so little desire to re-watch something I have already seen if there is something decent and new on the hard disk.

        I know children are different so if I had those I could see having recordings for them, or more hard disk space on a networked box.
    • While I see the occasional need for 2 tuners, frankly sometimes even that sounds like overkill... 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.

      Well for a start if you had multiple tuners you'd fill up a lot more disk space. Don't forget that TV schedules are still very time-oriented so that similar programs are broadcast in "parallel". Currently you tend to pick and choose; with a multi-tuner setup you can have it all available on time-shift so you'll tend to eat up (even) more disk space.

      Also, some programs are not available on DVD/VHS but you do want to store them for longer than a PVR will. A lot of (for example) home improvement shows like This Old House are useful to archive long term - if you're into home rennovation - but aren't easily available on VHS or if they are would cost a fortune to buy. I'll take a DVD burner option on my TiVo please.

      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.

      I agree, but here's the rub. Having more than one tuner makes a PVR simpler to use not more complex. I want to be able to tell my PVR to record programs X, Y and Z regardless of when they are on. With only one tuner I have to manually resolve the conflicts when they overlap in time. Companies like TiVo (and I assume ReplayTV) have done a pretty good job of building UIs for this but its still the single most complex and confusing part of using a PVR - perhaps aside from initial setup.

      Sometimes more complexity of the technology leads to a simpler user experience.
    • "a lot of it is at the video store for rent."

      And a lot MORE of it, particularly the really GOOD stuff (as opposed to the stuff they WANT to rent you), isn't at the video store, and never will be.

      I can definitely see a use for at least a couple tuners. If you're going to go, go all out, I guess.

      I'm still stuck archiving to CDR, so what do I know...
  • PVR Advice... (Score:5, Informative)

    by NanoGator (522640) on Wednesday January 22, 2003 @05:43PM (#5138877) Homepage Journal
    A dual 500 machine is more valuable as a PVR than a single 1.6 gig machine. Ideally you'd want 1 processor for playback and one to handle the other stuff (compression, etc...)

    16 channels? Err. Okay. If you really want to capture that many at once, you'd likely be better off having one computer per card. You don't need expensive/new hardware to do that. If the card does the processing and funnels the compressed data down to the hard disk, then the processor is little more than a manager. Last I checked, a P3 500 would easily handle a PVR card with hardware compression.

    If you have space considerations, go with a dual I suppose. But I wouldn't do more than 2-channels per PC.
    • What world are you living in? Last I checked, a P3 500 was encroaching upon the realm of realtime software MPEG compression at fair quality. And you want to use one of these for each stream?

      Insanity.

      I'll hazard a guess that such a "low-end" machine would have no trouble managing 16 MPEG streams, if you can find some way to plug all the hardware in.

      I mean, this isn't rocket science: Video enters tuner card. Tuner card handles MPEG compression, and produces something less than a 10mbps bitstream. Multiply by 16, and we're up to - wow - something less than 20 megabytes per second.

      Even once one includes requisite disk-shuffling, 40 megabytes per second of IO on a machine dedicated to the task is not a very demanding situation.

      But it's not easy or cheap to squeeze more than 6 PCI cards into commodity hardware. So, we're probably limited to 6 tuners per box, which amounts to something less than 15 megabytes per second of IO.

      I've got a P133 here which has no trouble pushing a paltry 15 megabytes per second around on the PCI bus. And, though I haven't checked, I can't imagine it having much difficulty achieving those rates alongside the overhead of software RAID (which is probably quite desirous for this application).

      Therefore, I submit that nearly any PC hardware still available for purchase today will easily sustain the throughput required to service as many MPEG encoders as will physically fit inside the machine. I welcome corrections to my submission.

  • by Omega Hacker (6676) <omega@nospaM.omegacs.net> on Wednesday January 22, 2003 @05:43PM (#5138885)
    Doing any of this without hardware compression is, of course, not even remotely viable. Given that, you have some serious limitations imposed by common hardware.

    Many of the PVR cards use the KFIR encoder chip in conjunction with a Conexant bt8x8 video capture chip. The bt8x8 does the NTSC->PCM, and sends it to the KFIR encoder, which sends the MPEG data back to the bt8x8. The limitation comes from the fact that there is no hardware-assisted DMA for the data coming from the KFIR chip. That means the host process has to repeatedly poll the PCI memory address for the bt8x8 GPIO ports in order to capture the data.

    Putting more than one or may be two of these cards in a single machine would swamp the machine so badly it wouldn't be able to do much else at all, let alone sending the video to disk or a network-attached storage device.

    If you can find a PVR card (supported under Linux, good luck putting multiple *anything* in a Windows box) that doesn't blow the PCI bus to pieces when capturing, and you should be able to put quite a large number in a single machine, limited by PCI slots. The KFIR chip captures up to 12Mbps, which is 1.5MB/sec. PCI can peak at 132MB/sec, so as long as busmastering overhead across a dozen cards isn't fatal, you could put them all in a PCI expansion cage on a single machine.
    • I may be wrong, but last time I checked, I thought that video4linux cards didn't necessarily support the level of hardware compression available on some cards.

      There's a question in and of itself: Which TV output/recording cards work well and quickly? With the low cost of various cards, would it be advisable (possible?) to reserve one for recording and another for playback

    • yes and where are you going to dump 132MB/sec coming off the PCI bus ?
      no hard drive or raid array on a PC can do that and no network can support that without using the PCI bus.
      motion.sourceforge.net sounds like a better idea.
  • TV Listings? (Score:3, Interesting)

    by AssFace (118098) <stenz77.gmail@com> on Wednesday January 22, 2003 @05:44PM (#5138895) Homepage Journal
    I have a TiVo right now and it is great.

    I've seen the software to do it yourself and also machines that also do it (but aren't the TiVo service).

    TiVo calls up a number every night and gets the listing information, is there a way to get that for the free programs and/or other machines?

    I know that TV Guide has a web page with the listings - do they have an XML stream that you can grab and parse - or someone else?

    If so, I'm not exactly a power user of TiVo and that would be a nice thing to have - but I don't want it as just a VCR sort of thing where I have to manually tell it "record XYZ at 4pm every thursday" - I am spoiled by the listings intelligence that TiVo has.

    If there is something out there like that, esp avail over the net, that would be a lifesaver when I move to Bermuda since they don't have TiVo there and I would love to have that or something like that there.
    • Re:TV Listings? (Score:2, Insightful)

      by p7 (245321)
      http://www.titantv.com is an excellent online program guide and it has a convenient downloadable data file for shows. I don't know if they cover Bermuda, however. There is also http://www.digiguide.com, but I have not really used the service.
    • Re:TV Listings? (Score:3, Informative)

      by ChaosDiscord (4913)

      TV Listings are available for do it yourself PVRs.

      If you're willing to screenscrape, you can use XMLTV [membled.com] to get your listings. The only potential problem is that if lots of people start screenscraping the free web sources are likely to try and stop people from doing so.

      If you're willing to pay for the service, you can use TVNow [unihedron.com] and pay $30 per year [tv-now.com] (about $2.50 per month, a fraction of what Tivo charges).

  • 5 PCs?!? (Score:5, Interesting)

    by nuxx (10153) on Wednesday January 22, 2003 @05:44PM (#5138897) Homepage
    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 (Score:4, Interesting)

    by nukey56 (455639) on Wednesday January 22, 2003 @05:44PM (#5138901)
    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.
  • Why not... (Score:2, Insightful)

    by The Gline (173269)
    ...just watch less TV?

    Not that you'll have trouble cutting down with the amount of utter garbage out there.
  • by ALecs (118703)
    how do you plan to get 16 NTSC-composite video signals from your cable/sattelite/broadcast feed? Do you have 16 base-band converters? I'm curious.

    Or perhaps are you capturing CCTV for archival? You may want to investigate how people do that (casinos capture immense amounts of high quality digital video for security purposes). The hardware is, doubtless, expensive, but it may give you some insight on how it can be done "on the cheap".
  • A cluster? (Score:5, Funny)

    by spoonist (32012) on Wednesday January 22, 2003 @05:46PM (#5138917) Journal
    "Think of a cluster of 4 PCs..."

    A Beowulf Cluster of PVRs? Sweet!
  • by noahbagels (177540) on Wednesday January 22, 2003 @05:47PM (#5138925)
    I have no great authority here, except that I have ran several linux systems, coded simple linux apps, and ran ATI's all-in-wonder (piece of crap) PVR solution for two years.

    Every month or so, someone comes up with a newfangled linux PVR and posts it here and on sourceforge.

    Last I looked, there were at least 4 seperate projects on linux PVRs. There was also something major wrong with each project!

    One project has a cool interface but could not actually record!

    One project could record and playback, but not record and playback at the same time!

    Yet another project could record and playback, but even the author of the thing reported that the audio and video were badly out of sync.


    Now: I don't know if the Ask slashdot question was a troll, or someone hoping to startup a dumb dot bomb that re-sells TV signals, but even a single P-1Ghz with an ATI all in wonder could barely record at broadcast quality - read: It didn't ever fully approximate broadcast quality.


    I've got two coworkers who purchased PC PVR solutions, and guess what - all three of us now own: Tivo, Replay, and DishNetwork-PVR systems.


    BAH. This is really stupid. Until someone hacks together something that actually works, and doesn't require a PHd in driver hacking, and syncs the audio properly, and has a 1/10^6 chance of working on someone else's build of linux/hardware, then let's not waste time discussing the *neato* applications of linux PVR. It's still a fantasy for private/OSS projects...
    • by ChaosDiscord (4913) on Wednesday January 22, 2003 @06:09PM (#5139094) Homepage Journal
      BAH. This is really stupid. Until someone hacks together something that actually works, and doesn't require a PHd in driver hacking, and syncs the audio properly, and has a 1/10^6 chance of working on someone else's build of linux/hardware, then let's not waste time discussing the *neato* applications of linux PVR. It's still a fantasy for private/OSS projects...

      Chill. Relax. There is no need for longwinded rants with random bold words. No, the free software PVR projects are not ready for prime time yet. It shouldn't be suprisingly, they're all very new. Mozilla's few few years weren't terribly promising. Linux itself took many years before approaching general usability. For the software to reach a polished stage we need to start with the crappy first pass. There is lots of experimentation and playing around. Core components (like drivers to TV cards and MPEG encoders) are still early in the development stages themselves. Eventually things will settle down, all but a handful of projects will fold, and things will become ready for you. In the meantime, let other people do a little harmless cheerleading. We need early adopters and fans to help work out the bugs in the system, do development, and keep the developers inspired.

      (If you feel a burning need to emphasize something, the <em> tag will generally give you a more subtle, easy to read result. Bold text tends to leap out, dominating the paragraph. If you really want readers to just focus on those key points, consider a bulletted list using <ul> and <li>)

      • You'll have something which just about performs the same as a VCR does now, but still doesn't have consistent, reliable, international scheduling information which means no season passes, wishlists, channel highlights, suggestions.

        Yah, it all makes sense now.

  • by teamhasnoi (554944) <teamhasnoi AT yahoo DOT com> on Wednesday January 22, 2003 @05:49PM (#5138939) Homepage Journal
    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.

  • by orichter (60340) on Wednesday January 22, 2003 @05:52PM (#5138964)
    orichter writes: does anyone know how, with a with a few minor adjustments, you turn a regular gun into five guns?
  • Doesn't Ultimate TV already do this, the multi channel that is. Get 2 and I'm sure you're still cheaper then 4 computers, though if you need to tape more than 2 channels I think you should really watch less tv
  • by Tackhead (54550) on Wednesday January 22, 2003 @05:53PM (#5138976)
    Can we get the turnkey single-channel Linux PVR first? :-)

    Word to developers - what you've done so far is great, but if you want to unseat MSFT, you've gotta make it so that Grandma can install it.

    If we were talking about a new version of GCC or the latest kernel, with Visual Studio.NET and Windows Longhorn as the competition, it'd be fine to moderate this comment as (-1, Lazy n00b), but you're talking about a glorified VCR, and you're going up against TiVO.

    For this kind of product, User Interfaces matter. Saying "RTFSource", and "It's skinnable", won't cut it.

    Likewise, dependency trees can be a formidable barrier to adoption. Saying "Well, of course it compiles fine for me, I mean, who doesn't rebuild XFree86 from the CVS source tree on a weekly basis?" isn't gonna cut it either.

    PCs are cheap enough these days, especially since folks in the DIY segment might want to dedicate one as a PVR. Given the appliance-like nature of such a device, I'd say a (set of, for each supported motherboard-chipset/video-chipset combo) binaries ought to be a design goal, and I might even go so far as to say that distribution as an ISO wouldn't be out of the question.

    • Can we get the turnkey single-channel Linux PVR first? :-)

      Word to developers - what you've done so far is great, but if you want to unseat MSFT, you've gotta make it so that Grandma can install it.


      Am I not the only one who absolutely hates these patronizing comments? They are just so typical from users of free software that wish to contribute nothing yet do nothing but pester for features. I take it the above poster has posted many a time to developer lists or developer IRC channels the "HELP! IT DOESN'T WORK" posts without reading any of the docus or anything.

      Well, here's a bit of a news flash: OS developers do not give a rat's ass about unseating MSFT (why you have to use the stock symbol, I do not know). We like to code! That's it. For most of us, it's not any kind of religious thing. Sure, we want people to use the software and benefit from it, but we personally care less if Grandma (or you for that matter) can install it without doing any sort of due diligence.

      User Interfaces are a myth. The Windows interface is only intuitive because they give you no other choice than to learn it. OS developers give you an option not to use it, and you bitch because it doesn't behave exactly as MS's version does. If you really care, either 1) do it yourself or 2) send someone else money to do it if you don't have the skills.

      BTW: As far as I'm concerned, mocking script kiddie speak is just as bad as speaking it.
  • It would be cheaper to just live with a single PVR for day-to-day recording, and buy DVDs and/or VHS tapes of the content you want. You might not be able to catch all of your desired programs, and it might not be possible to order all of the content you miss on DVD or VHS, but it certaingly is more simplistic and cheaper then building a friggin cluster and hacking code in order to tape stuff off TV.
  • Err, this may be a silly question, but where are you going to get the CPU power from to encode 4 video streams?

    My 1Ghz Athlon is at 80% encoding HALF-frame video into MPEG4 and it drops seriously large numbers of frames if I try and encode at the native resolution (720x576 for UK PAL).

    I tried using MPEG2 but that uses up seriously massive amounts of hard disk space, just to get it up to VHS standard.

    Unless someone makes a hardware MPEG4 encoder, I can't see how you can easily encode 4 video streams at once unless they're done in a fairly low quality/resolution.

    Nick...
    • Re:CPU Power (Score:3, Informative)

      by geekoid (135745)
      go to SCSI 160, use at least 3/4 G Ram.
      Thats what I have in mine, and it record Native just fine.
      • I have no problem with disk speed or memory - my point was regarding CPU utilisation which adding faster disks and more RAM doesn't fix.

        You probably have a faster processor or you're happy to put up with lower video quality.

        Nick...
  • by geekoid (135745) <dadinportland AT yahoo DOT com> on Wednesday January 22, 2003 @05:59PM (#5139025) Homepage Journal
    Many people are posting things like "I can't see why you oould need 16 channel".
    why would you post just that? I show a starttaling lack of imagination for nerds.
    Just off the top, I can think of:
    Archiving different channels takes on global events.
    Perhape he is going to take 'orders' for recording, so instaed of settng your VCR, you just call this guy up and say "PLease record X for me"
    Maybe he just thinks its interesting.
    Perhaps he's going to hook it up to 16 continues camera feeds for security.
    I'm sure some people here can think of more, and better ways to utilize this.
  • I seem to remember reading about a guy who was recording the signal before it got to the tuner. Then he played it back into the tuner and selected the show he wanted to watch. He had recorded all the available channels at once.

    I read about this a long time ago. Probably back in the 1970s because I think it was when VCRs were coming out and the idea of recording a show was a new idea.

  • One reason I can think that you might need this many channels would be if you were streaming a feed to a corporate or dorm LAN. OK, so the poster didn't mention streaming they mentioned PVR, but lots of people are asking "why do you need that many?". Well, that's a reason.
    Now, can anyone point me towards a decent media streaming solution for Linux please? (I'm serious!)
    Thanks, Matt
  • ...is a Beowulf cluster of PVRs?

    sorry, but it had to be said.
  • by t0qer (230538) on Wednesday January 22, 2003 @06:07PM (#5139084) Homepage Journal
    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.
    • That is basically how Bit Torrent works. It send the entire file to a few main host files, who in tern share it with the next tier down, who share it with the next tier down, etc. Basically, as soon as you start downloading the file, it is being shared withthe next person in line. So you are simetaneously uploading/ downloading. It is actually an interesting method of transfering files. And has some potential to get files distributed quickly.

      Of course, that is deopendant of the number of users, downloading the file. And a few other things. But it is an intersting concept.

      Try doing a search on google for Bit Torrent, I THINK that comes up with the best results.

      - Ice_Hole
      • Funny,

        i'm downloading something from torrent right now. 1394.1 MB, it was slow at first, but now i'm steady at around 22kb.

        Thing thats cool about BT is it's very easy to become a seed node. I d/l the FBSD 5 iso's from a FTP source before finding the BT source. Since i'm such a nice guy I shared my ISO's simply by clicking the link on the FBSD BT page and saved it where my previously d/l iso's were. Whammo I was a BT seed for 24hrs.

  • sigh (Score:2, Insightful)

    by ilsie (227381)

    I've seen a lot of threads that say an application like this would be great for security cameras and the like.

    Assuming this is even implementable (which it is not), lets look at a cost breakdown:

    16 video capture cards - $100 x 16
    16 120 gig hard drives - $120 x 16
    4 cheap cases - $50 x 4
    4 mb/proc/mem combos - $240 x 4
    1 dvd burner - $200 x 1
    other odds and ends - $100
    which comes out to a grand total of approximately, oh, $5000

    Now lets look at my solution:
    16 VCR's purchased from circuit city- $50 x 16
    one guy to switch tapes every six hours- $6.50/hr

    $806.50.

  • by Ice_Hole (87701) on Wednesday January 22, 2003 @06:10PM (#5139100) Homepage
    Digital cable is basically just another way to modulate a given 6 mhz block that we call a channel. It makes this block able to carry multiple channles, dependant on the quality, and compression. A highly compressed channel can handle up to 40 channels (Of the cooking show variety), and a minimum of 4 (Die Hard quality).

    But this is what I propose. You would have to get a card that is modded to recognize these blocks of channels (They all recognize the channels, but they won't recognize the individual digital channels, unless they are digital cards). BUT, take these cards, and record the 6mhz bandwith, NOT the actualy individual channels.

    Lets put it this way, lets say HBO runs at the 550 mhz - 556 mhz range (Which is arrpox where it is for COX Cable Las Vegas) If we were to recorde this range, we would not just be getting the normal HBO that we want, but also all of the other channels on the same bandwith. On average thir are 8 high quality streams on any 6 mhx channel. So in this case, by recording one of these channels, we would be able to extract 8 channels, say HBO, HBO2, HBO Signature, HBO Latina, Cinemax, etc.

    In this case, it might be able to record between 8 and 40 channels per tuner card. With specially modified hardware, and software to do this level of decodeing.

    Also if you were to find a way to compress this data, you might be able to find an extremely efficient way to compress this data.

    - Ice_Hole
  • I told you on the last Tivo story, "Imagine a beowolf cluster of these."

    You all kicked my ass but see... He listened.

  • A waste... (Score:3, Funny)

    by ryanvm (247662) on Wednesday January 22, 2003 @06:19PM (#5139185)
    I'm sorry, but what is the point of 'Ask Slashdot' if the question is going to be absolutely silly? I've farted out more useful questions than this one.

    A PVR that can record 16 channels at once? Get real. Unless you're operating a TV station, you don't need that many channels. And if you do operate a TV station and you're asking Slashdot how to build video equipment - you're fucked.

    Here's a tip kid. Quit jerking off thinking about recording 16 TV shows at once and go outside.

    [And yes, I've got Karma to burn.]
  • MythTV (Score:3, Informative)

    by brent_linux (460882) on Wednesday January 22, 2003 @06:29PM (#5139296) Homepage
    Development is currently in the works for mythtv [mythtv.org] to do this. Hopefully 0.8 release will have this in it. Isaac and crew are working on it.
  • by digital photo (635872) on Wednesday January 22, 2003 @06:32PM (#5139332) Homepage Journal

    Given enough money, anything is possible.

    If you want to reduce the number of nodes, you need to increase the capacity of each individual unit. One way of doing that would be to use a PCI backplane with a motherboard "card". This would give you more than the 4 or 5 PCI slots on most motherboards.

    Go with a FireWire or USB2.0 capture device instead of a capture card. You can connect 4 capture devices to a 4-port FireWire or USB2.0 PCI card. So, if you only devote 3 PCI slots to your input sources, you still get between 6-12 concurrent input streams via FireWire or USB2.0. The problem is finding a TV tuner you can control via software through the FireWire and USB2.0 links. But that would solve your problem of recording alot of different shows at the same time with fewer CPU count.

    If you plan on having the storage local, you'll want to go Raid. Hardware Raid would be better than software Raid.

    If you use a seperate machine for storage, I'd go with NFS or netcat over GigaEthernet to a FileServer with striped volumes on mirrored or Raid-5'd disks. netcat would be better since it has lower overhead than NFS.

    So, with 2 Computers, you will be able to capture from 1-12(depending on how many cards and ports you use) individual channels/sources to a very fast file server which can then serve out the streams or burn them locally to DVD(s).

    ADC, Canopus, Sony, and a few others produces AVFireWire/USB2.0 adaptors, but they are for signal source and output and not for tuners/channels. Some resources listed below:

    Resources

    WinTV Products:

    http://www.hauppauge.com/html/usb_data.htm

    A USB TV Tuner

    http://www.snapstream.com/buy/buy-tunerusb.htm

    More USB TV Tuners...(wintv repackaged)

    ATI Wonder USB

    http://www.ati.com/products/pc/tvwonderusb/

    http://shopper.cnet.com/shopping/resellers/0-114 36-311-3850079-0.html

    ATI usb tuner card...

    Basically, they are USB tv tuners which captures to MPEG1 or MPEG2... if you're running under Linux anyways, you can re-pipe through Mjpegtools to resize and recompress to MPEG2 format for use with DVD playback on the fileserver.

    But yeah, it's doable. :)

    Good luck and have fun!

  • There are a few shows on TV that I think are almost worth watching. However, the thing I really hate about television is that I have absolutely no control over when I watch what. I am at the mercy of the networks for my scheduling. I think that it would be beneficial (particularly to us geeks, but I think, to the public in general) to make a transition our video consumption away from the broadcasted TV signals, the few to many distribution method, and move towards using what we have on the internet, the many to many distribution.

    One way, perhaps to speed this transition, which I would consider a form of activism, would be to set up such a grand TV ripping station and every week let's say, burn a few CDs/DVDs for different types of people. A disc of cartoons, some friends are mine are into sports so we'll burn one for them too, and of course the news, and C-SPAN and whatever else we feel like. Not to mention of course, all the movie channels.

    This would of course, be highly illegal and expensive and make no money, but I think it would be a grand gesture in the fight against intelectual property. Cheers, Joshua

  • YOu just need a really large bandwidth converter, then you could record the entire spectrum and when you play it back later, you can tune in different stations. Not remotely practical today, but in a few years, who knows?
  • by anewsome (58) <anewsome@an e w s o m e . com> on Wednesday January 22, 2003 @06:52PM (#5139511) Homepage
    Really if you need 16 channels at once, my first thought would be why? But assuming you have a sane answer to that I'll tell you a little about my setup. Which is able to record 2 channels at once direct to hard disk, while watching at least 4 seperate channels on other TVs around my house, all using a single satellite dish (dual LNB).


    Also, I am curious why you would want to use MPEG encoder cards to record your video. If you've ever tried this, you would quickly realize MPEG is a REALLY bad format to use if you plan on editing your video. I assume you will be editing your video right, I mean who and the hell would want to burn TV programs, commercials and all, straight to DVD with no editing. Anyway, editing MPEG video, no matter what you use is a bad proposition.


    My system, which is two low power PCs with various large (300GB+) multidrive RAID arrays, firewire cards, 1 Canopus ADVC-100 on each system and Sony Satellite receivers. The Sony are important since they have a 9 pin serial connector which connect directly to the PC for changing channels and controlling the satellite receiver.


    This system works flawless and I have recorded around 1,500 TV Shows since late 2001. My Linux based recording solution prior to this was moderately reliable but the quality was not good enough for DVD. With this setup the quality of the burned DVDs are almost indistinguishable from the broadcast source. In other words, very good. Oh by the way, my interface for scheduling is custom web interface using Mysql for storing data.


    Now I suppose if you were hell bent on it, you could put multiple cards in a few machines and run multiple capture processes to grab your insane 16 channels, but that would be one busy machine. I would recommend a more sensible soultion, one like mine would probably work nice.


    My setup includes 2 machines for grabbing video straight to disk in DV format (very high quality, does not degrade with editing like other lossy compression methods). Now these machines also double as mpeg encoders too, but don't do much else. They stay pretty busy with just those two tasks. I have another 3 machines that are dedicated MPEG encoders, using mjpegtools as the encoding software. My desktop machine is where I edit the video, using Kino. I also use my desktop to run dvdauthor, which masters the DVD-Video folders prior to burning them to disk. This machine sometimes encodes MPEG too. On some days I have as many as 6 or 7 MPEG encoder machines going. And I have yet another machines that actually burns the DVDs.


    So I guess you could do it with a few machines, but you'll be sorry once you've got a bunch of video to encode or master and only a few CPU to do it. Make your capture machines the cheap, slow CPU type and your encoder, editing, mastering machines of the fast type and you might be all right. I'd still love to know why you would want to record 16 channels. Also, I assume you are doing this with Cable TV, which sucks for quality and regular cable too, since digital cable requires a box for each individual channel you need to watch at the same time. I can't see anyone paying for rental on 16 cable boxes. Even worse I can't see anyone spending that much money on 16 satellite reveivers. I have 6 satellite recievers and I almost cried when I had to pay for them.


    Oh by the way, my system is 100% Linux end to end, so the poster who posted a comment above who says there is no Linux PVR solution that works, has no idea what he is talking about.


    -Aaron.

  • I'd get a Radeon(flavor of the month) All In Wonder, 2 TV wonder cards(Does it have hardware MPEG encoding support? if not, substitute both TV wonder cards and Radeon All in Wonder for 3 cards that do plus one really kickass video card), an IDE controller card(Go with a mobo with decent onboard SCSI or likewise an external SCSI adapter if you have gobs of money to throw around), 3 really fast and rather large hard disks(This is where the SCSI optional comes in.), 1 rather slow and small IDE hard disk, a high end 5.1 capable soundcard(I'd suggest Soundblaster Audigy but I hear it's XP/2k drivers are a dog...), a gob of RAM(1GB+), and 1 DVD-R. Load the entire thing onto your choice of Mobo/CPU combo, and go with it. And of course, the necessary wiring. Enough coax from the wall to the system, a 3 way splitter, and soforth.

    here's the only problem, how do you capture from three seperate sources at once? Maybe you could rig the ATi multimedia center to run several instances each pointed towards the different capture boards? Maybe ditch windows all together and find a linux solution?
  • Instead of ripping on this guy for watching too much TV, maybe you should think about what else this could be used for. I myself looked into setting up something similar for my frat. Basically we wanted a web-driven on-demand video system. The outputs would be RF modulated and spit over unused channels on the pre-existing coax cable. Basically a pirate CC TV station with 24 hour Simpsons, Futurama, and Family Guy.

    Unfortunatly it turned out to be cost prohibative at the time (2 years ago) and we just fell back to a bunch of samba shares and watching TV on computer :(
  • Which TV tuner card(s) with hardware MPEG2 encoder are actually supported under Linux? That is a big showstopper as far as I can see...

  • An array of PVR's? What in the world are you going to watch? There aren't enough good shows on on to keep a single PVR busy let alone an array of them.

    Me? I'm going to build an array of vacuum cleaners. My idea sucks too, but will cost less. ;)
  • I dunno about using TV tuner cards, which have been a real pain-in-the-butt when I had to deal with them, but I did find it easy to hook up my DV-camcorder to my PC through a Firewire (IEEE 1394) card & then essentially save the video stream from the camcorder directly onto my harddisk. The camcorder would also automatically send any analog video source I hooked up to its video inputs straight to the Firewire connection, real-time.

    The camcorder provides the video stream in MJPEG format (which would probably need to be reencoded to something a little more standard, but that could be done at leisure and perhaps other machines).

    If you've got a powerful-enough PC, it should be able to handle a couple of simultaneous Firewire streams. There's probably some way to do the video/audio->Firewire conversion w/o a camcorder too. There might also be video/audio->USB converters (as long as your USB connections have a high enough bandwidth to handle a decent quality stream).
  • Anti-TV Religion (Score:4, Interesting)

    by nathanh (1214) on Wednesday January 22, 2003 @09:33PM (#5140687) Homepage

    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.

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