[mythtv-users] Backend for Multiple HD/Firewire streams

Pat Mac patslists at gmail.com
Wed Mar 9 12:51:26 UTC 2005

I'm planning to convert my current p3 1 Ghz standard definition
backend into a firewire/hd backend (ATSC) and I just want to make sure
my thinking is correct.  I don't want to convert this and then find
out I was off by a factor of 10 and my PCI bus is saturated.

1.  Firewire & OTA streams come in at a max bitrate of 19.3 Mb or ~2.4
MB per second
2.  Without gigabit ethernet, I can connect at max 4 frontends
3.  With multiple frontends I'm probably better off throwing a RAID in
the machine as well to maximize disk speed.
4.  Even with 4 streams coming in, 4 streams going out, and a hardware
RAID on the same PCI bus I'm not even close to maxing out the PCI bus
because I'm streaming in at ~10MB/sec, writing ~10 MB/sec to disk,
reading ~10MB/sec from disk, and writing ~10MB/sec to ethernet leaving
me with ~93 MB/sec still available on the bus and nothing to worry
5.  Because the ATSC streams arrive pre-compressed in MPEG2, my system
will have no problem handling 4 of them since there is very little
processing going on

Am I missing anything major here before I start?
Also, if anyone has Time Warner with a 3250, does the TW OSD show up
in the video from the firewire port?  Can you set the output format
(say, send every chanel at 480p)?

Thanks to everyone for the great system.
Long time listener, first time caller.

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