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Building A Small Video-On-Demand System?
Ryan Mack asks: "My dorm is looking to build a small (4-8 user) Web-based video-on-demand system. Basically, we'd want to be able to schedule MPEG-1 or MPEG-2 streams to be decoded and sent over our building's unused cable TV distribution system. There are many PCI MPEG decoder cards, but few advertise Linux driver support, and none mention if multiple cards can be run in a single box. We've also looked at external MPEG decoding devices, but these require ATM, T1/E1, or high speed RS422 connections, which also raise Linux compatability concerns. Anybody done this before? Can anybody recommend a MPEG decoding card or a RS422 controller capable of 5 Mbps transfer?"
Having worked a TON on software MPEG playback, I know that MPEG-2 playback in software is ENTIRELY POSSIBLE with readily-available software at, say, 700 MHz. Think videolan.org, XMovie, and OMS (linuxvideo.org).
And I've heard from a reliable source (who shall not be named) that some people have gotten an Athlon 800 to play four (FOUR!) broadcast-quality MPEG2 streams at once.
I shit you not.
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I am by no means an expert on this subject, but why use a dedicated MPEG decoding piece of HW?
It would seem possible to use a low-end PC with a TV-out board, and SMPEG to output it out.
Maybe I am missing something?
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oh yeah, the name of the board is the 4-REELTIME RGB
Looks quite cool, only problem is they want to use CATV distribution; This provides for MPEG2 streaming and decoding, which means each room would still have to have a reasonably beefy PC to act as decoder.
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Most offboard MPEG1/2 decompressors require an ATM or RS422 host connection. ATM is expensive junk, and RS422 has a nominal guaranteed throughput of 5Mbps. Most host cards will not guarantee this, nor ever reach it, however.. (As for why; I assume they're going to rip their combined DVD collections to disc. Disk space is dirt cheap these days. Get a good bargain on unflashable 40G ATA66 drives and you're set..)
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Just hook up a DVD Player or VCR to it and broadcast the video.
I know it's not as sexy, but it's cheap.
On the other hand, get yourself a couple of TiVos (runs linux) and hook them up, hack the system so you can control it over the serial or use an infrared repeater of some kind, perhaps even web controlled using the ethernet hack.
For more information, look at Tivo-Underground at www.tivocommunity.com
If you're talking about sending out multiple MPEG streams, I would recommend using BeOS, as it can handle large, multiple media files without a hiccup. For a starting point, head over to the
"Audio & Video" section at www.betips.net.
True, it isn't free in the RMS sense, but when it comes to handling media with grace under fire, BeOS wins out.
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The LML33 would be great, but is also expensive. I don't know what you're aiming for though.
Disclaimer: I have NO connection with LML.
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Perhaps we can get the makers of "tvtool" to port it.. :-)
While a hardware decoder would be ideal, a software decoder would be a nice start, but first I need TV out.
Sounds like you want to build a mini "head end" for a CATV system and stick some PC's decoding MPEG streams on the end of it. You'll send commands to the video servers via Ethernet or some-such, and send the streams into RF modulators and onto the CATV lines.
I'm fuzzy on the RF modulator part (I've worked with using ONE RF modulator on a line-- but I know that there exist solutions that will allow you to pile multiple signals from several RF modulators onto the same wire)-- but that would really be the hardest part. We did a "closed circut" system in a school where I interned a few years ago-- but that was done over CAT 5 w/ some type of balun on each end and only one RF modulator in the mix.
I'd recommend foregoing hardware MPEG decoders and get some el-cheapo PC's that have enough horsepower to decode the streams you're looking to decode. Boot 'em diskless w/ a server hosting all the encoded files. Stick a video card w/ reasonable quality TV out on each PC, put 'em on an Ethernet switch w/ an uplink to your building LAN, plug 'em into the RF modulators, and you should be set to go.
I don't think you're going to find a cheap way to do this, unless you can come up w/ some cast-off RF modulators. You're talking about hardware that doesn't have a tremendous non-professional market (not many people run their own CATV system) so it's not cheap. Sounds like a fun project, though.
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this usually blows, but, I have to answer your Q with a couple. MPEG1 is best done at 2Mbps. MPEG2 is best done at 6Mbps. (these are best bang for the bit #'s) Why r u looking for 5Mbps? Software based decoding usually maxes the proc with an MPEG1 @ 2Mbps. I am unaware of a Soft based MPEG2 decoder. Try VisualCircuits. They have a card that is a 4 port output(composite Video/Stereo Audio) that will decode MPEG1/2. Oh yeah, you can load one box with up to four of these buggers. yeah yeah, it runs on NT the best, but Linux dvrs are coming...so they say. of course, being able to play back MPEG'd video precludes that fact that you need coded media to begin with. Are you being provided with the crushed video or or you encoding it yourselves?? With what hardware?
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From the home page: "broadcast video on the campus, and provide the students with a MPEG2 software decoder. It will support streams from a satellite, a DVD or an MPEG2 compression card."
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There's a lot of ways to pull this off. How much engineering experience do you have? You can hack this together as well. Tivo boxes are pretty cheap, you can stack multiple Tivo boxes, modify the code so you don't use thier service. Use a Linux server to activate the servers.. That's a hacked approach. To play 8 DVD movies at the same time would require some serious horespower, even with hardware dvd decoding. It might be easier to set up multiple On-Demand channels and have set movie times. I worked at a University as a Sysadmin, one dorm was planning on digital on demand. Movies were viewed on the users computer or a tv/monitor atached to the video out. Check the net, there is plent of open source for video on demand. Possibly you can aquire 8 Creative Labs DVD driver (They work with Linux)
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It seems strange what you are doing (uplink to select the video to be streamed via a web interface, downlink to a TV via coax - maybe it is a bandwidth issue?), but how about this:
For a simple MPEG stream (like say from a VCD), simply set up some cheap Pentium 133 boxes, one per each user, with each one having a means to output the video to a TV (like a video card with TV Out and a composite->RF converter). Network them to a faster fileserver with the big drives to store the video.
If you get the right motherboard (like a MediaGX motherboard, or similar), that has built in ethernet, video and TV-Out, you could mount the eight boards in a custom case, perhaps even net boot them.
This solution isn't the most elegant, but it would be cheap enough.
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