[mythtv-users] PVR Hardware
gavin at nodecaf.net
Thu May 5 22:13:19 UTC 2005
Maybe I'm sort of missing the point here, but why so stressed about the delay from live TV? Honestly, my wife and kids use my Myth box and the only time they even notice the delay (that they've mentioned) is when changing channels. This causes a 3 second delay or thereabouts while live TV is cached before the channel "changes". Of course, I know the channel has already changed... but that's a detail you live with on any PVR, be it Myth, TIVO or any of the "pretenders to the throne". My wife and kids seem quite happy to deal with the slight delay for the sake of pausing and rewinding live TV.
My setup is a satellite box attached to my Mythbox through an S-Video connection for video input to a PVR-250 card. Channel changing is done through a serial cable to the back of the satellite box. I use the guide built into Myth now instead of the one on the satellite box... in fact everything's done through Myth now so I find the delay is such a non-issue.
Catpure Cards: BTTV *might* result in slightly less delay on live TV if you recode Myth to override the 3 second built-in delay. May or may not be worth it as in the event your machine gets pegged on the CPU or you have a glitch on your disk subsystem, you're more likely to get a glitch in your TV viewing. Not perfect. Also, BTTV just sends raw frames down the PCI bus... which dependent upon other cards in your system may actually saturate the PCI bus during high traffic loads. The advantage of capture cards like the Hauppauge is that they send only MPEG2 data (pre-compressed) down the PCI bus, therefore saving data bandwidth. My first ever Myth-type box used a BTTV card... it sucked because (as I later ascertained) I had a badly behaved bus-mastering gigabit Ethernet NIC in another slot that was causing latency to other cards on the bus. Now I use a PVR-250 and have been very happy with the results. I do have some apparent traffic problems, but I attribute them more to my disk subsystem which is rather slow than I do the card. 3 BTTV cards on the same bus might be a problem... I'd get onto doing some mathematics on raw frame speeds down the PCI bus.
Basically, as far as the frontend, you can get your technical requirements (fanless, quiet, flash hard disk), but not for less than $200! Even fanless and quiet with a hard drive is going to cost you more than that realistically. Be realistic about your requirements. Myself, my frontend is also my backend... but when I get around to doing a dedicated frontend I'm going to spend a few more bucks and get quality and quiet hardware.
Hmm... for a frontend you perhaps might want to consider a modified XBox (chintzy solution IMO), or a fanless machine using PXE boot to your backend. Works great, but boy, if you lose your network connection...
From: mythtv-users-bounces at mythtv.org on behalf of James Rose
Sent: Thu 5/5/2005 3:35 PM
To: mythtv-users at mythtv.org
Subject: [mythtv-users] PVR Hardware
This may have been answered many times already, but searching the lists
(and google) didn't seem to help too much.
I'm wanting to build a distributed myth setup (ie one mythbackend and two
mythfrontends), and I'm wondering:
1) What is the best recording card to use? I've got lots of experience
with Hauppauge PVR-350s (I built a 4 channel recorder..w/o myth), but I
find the delay completely unacceptable for live tv. I haven't played with
IVTV since version 1.9, so maybe this is fixed (seems to be a hardware
issue though). Acceptable delay to me is <1 second. I'm willing to trade
quality for speed here since I'm recording analog cable to begin with. My
only other requirement is that it does hardware recording, since this box
is also my web/mail server (machine is a 2.8GHZ AMD with 1GB RAM, and
400GB IDE with RAID6/LVM on Debian Sarge). In addition, I plan on having 3
recording cards in the box. Are the BTTV devices in general faster than
IVTV? Can all this even be accomplished at this point in time?
2) What's the best compromise for mythfronend systems. I've read a lot of
mixed reviews on using xboxes/ps2s. I'm wanting something really cheap
(around $200/box), and extremely quiet. I'd like fanless, and may skip
the hard drive and go with flash memory.
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