[mythtv-users] Tuner Card w/ Svideo Inputs & PCI Sound Transfer

Ian Neubert ian at ianneubert.com
Fri Jan 23 14:24:40 EST 2004


Henk Poley wrote:
>IMHO, your setup won't work... Splitting it up into 2 backends (and
>preferably a seperate frontend) would do.

Joseph A. Caputo wrote:
>As to whether your machine would be able to handle 4 PVR-250s + 1 pcHDTV
all
>recording at once, you are right in that the limiting factor would be disk
>throughput.  I suspect you might hit a bottleneck there... that's an awful
>lot of data to be writing at once.  Also, you need to leave some room for
>playback read access; even if your frontend(s) is/are on another
machine(s),
>the stream still needs to be read from disk.  Time to do some disk
>access/throughput calculations!

Looks like I'll probably use multiple backends. I'll definetly have seperate
front ends, the plan was to drive 4 front-ends running live tv at the same
time, lol. That's a heck of a lot of bandwidth on the pci bus and the disks.

Let's say I was recording in MPEG4 @ 640x480, which is ~2 gigabyte/hour or
4.55 million bits/sec times 4 streams = 18.2 million bits/sec. According to
Seagate a Barracuda 7200.7 SATA can handle an Avg. Sustained Transfer Rate
of 32 - 58 million bytes/sec, or 256 - 464 million bits/sec. I was going to
do a RAID0 so it seems like it could handle it. That doesn't include the
loss of performance due to multiple streams being written, but I guess I'll
just have to give it a shot and see what happens.

The PCI bus will brobably get the workout. Thanks for the tips! They're been
very helpful.

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............ian...
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www.ianneubert.com



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