Mailing List Archive

Dual Card CPU experience
I've been using Mythtv since December and its really showing its promise.
Most of this time I've been using it on a dual P2-450 with 512Meg and 3
hard drives (2 - 80MB/sec scsi and 1 ide) that I had laying around.
The machine is setup almost perfectly, 2 Hauppauge 401 cards both using
btaudio, irman remote, NTP, DSL internet, etc.
It really showed its value while watching the war coverage.
The only small gottcha is I have to keep the encoding settings rather low
because of the low power CPUs. My settings are
640x240 using RTJpeg @ 200 / 0 / 0. Audio sampling @ 32000, no sound
compression. And the P2 can't do the deinterlacing playback either. File
sizes are 2-3+ GB/hr (effects of stereo uncompressed sound).

With these settings, it can *usually* record 2 shows and play a third with
only few/modest skips. Viewing quality is still surprisingly ok
despite the low resolution, even on a 43" HDTV.
Both CPUs are pretty much maxed out, running
80-100% ea. Don't kid yourself tho, TV content *does* matter; not all TV is
the same. Try watching a Boston Celtics BB game on the home court and you
will see what I mean :)

So now as I start designing a new dedicated myth machine, I was hoping to
get some more experience from other dual encoder card owners on their
experience. My ideal goal would be recording 2 and playing a 3rd show
at 640x480 using better quality mpeg4. I'd especially be interested in
experiences with faster Athlons (2400+) or fast P4/Xeons. Can people
crunch all this on 1 cpu, or am I kidding myself and should stay dual. I've
seen where the author claims to *almost* do 2 x 480x480 encodings and play
a third on a 1800. And lots of people claim 50% or less usage on faster
Athlons with 1 card, but from my experience 2 cards imposes a lot more timing
issues that buffering just can't completely overcome. Its hard to beat that
2nd cpu.

One more comment, I'm very encouraged about the PVR 250/350 progress,
but to be on safe side, I'm assuming software encoding for right now and
will apply that factor in later. Truely far-fetched, I'd also like this
machine to someday handle a HDTV timeshifting also, but that's a ways
away for lack of ATSC cards in Linux.

I'd appreciate any experience people may have.

Thanks,
Brian
Re: Dual Card CPU experience [ In reply to ]
<snip>
> experiences with faster Athlons (2400+) or fast P4/Xeons. Can people
> crunch all this on 1 cpu, or am I kidding myself and should stay dual.
> I've seen where the author claims to *almost* do 2 x 480x480 encodings and
> play a third on a 1800. And lots of people claim 50% or less usage on
> faster Athlons with 1 card, but from my experience 2 cards imposes a lot
> more timing issues that buffering just can't completely overcome. Its hard
> to beat that 2nd cpu.
<snip>

I'm using two Hauppage 401s on an Athlon 2100 with a single WD 200GB drive.
It can simultaneously encode two 480x480 RTJPEG at quality 170 streams and
play another nearly flawlessly. Dunno about cpu usage, though.

The only problems I've noticed are:
1. When the second stream starts encoding after the first stream has been
encoding for a while, it will cause the the first stream to run in slow
motion (missing a bunch of frames) for about 1-2 seconds. Audio is fine
during this glitch. Once the second stream gets going, everything runs great
with no glitches.
2. I have a purge script that runs via cron every half hour. It checks
whether the hard drive is nearing full capacity. If it is, it automatically
deletes the oldest file. This can cause the same effect mentioned above for
1-2 seconds.

Mike
Re: Dual Card CPU experience [ In reply to ]
I wouldn't recommend anything less then a 2400+. I o/c'ed my 2400+ to
2.13Ghz which pushed me just over the edge to record two programs at
512x384 mpeg4 @ 3000bit rate, Max: 1 Min: 5 Diff: 3, and MP3 41200Hz
encoding at 7 quality and watch one recording at the same time.

The only time I notice frame drops is when another recording is just
starting, but it doesn't happen all the time. I think if I bumped my ram
up to 512 (from 256) it would help solve this issue.

On Wed, 2003-04-23 at 21:20, Brian Foddy wrote:
> So now as I start designing a new dedicated myth machine, I was hoping to
> get some more experience from other dual encoder card owners on their
> experience. My ideal goal would be recording 2 and playing a 3rd show
> at 640x480 using better quality mpeg4. I'd especially be interested in
> experiences with faster Athlons (2400+) or fast P4/Xeons. Can people
> crunch all this on 1 cpu, or am I kidding myself and should stay dual. I've
> seen where the author claims to *almost* do 2 x 480x480 encodings and play
> a third on a 1800. And lots of people claim 50% or less usage on faster
> Athlons with 1 card, but from my experience 2 cards imposes a lot more timing
> issues that buffering just can't completely overcome. Its hard to beat that
> 2nd cpu.
>
> One more comment, I'm very encouraged about the PVR 250/350 progress,
> but to be on safe side, I'm assuming software encoding for right now and
> will apply that factor in later. Truely far-fetched, I'd also like this
> machine to someday handle a HDTV timeshifting also, but that's a ways
> away for lack of ATSC cards in Linux.
>
> I'd appreciate any experience people may have.
>
> Thanks,
> Brian
>
>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users@snowman.net
> http://lists.snowman.net/cgi-bin/mailman/listinfo/mythtv-users
--
Mike Benoit <ipso@snappymail.ca>
Re: Dual Card CPU experience [ In reply to ]
On Thursday 24 April 2003 08:40 pm, Michael D. Cencula wrote:
>
> I'm using two Hauppage 401s on an Athlon 2100 with a single WD 200GB drive.
> It can simultaneously encode two 480x480 RTJPEG at quality 170 streams and
> play another nearly flawlessly. Dunno about cpu usage, though.
>

It would be great if you could watch a top session for a few minutes while
doing this.

> The only problems I've noticed are:
> 1. When the second stream starts encoding after the first stream has been
> encoding for a while, it will cause the the first stream to run in slow
> motion (missing a bunch of frames) for about 1-2 seconds. Audio is fine
> during this glitch. Once the second stream gets going, everything runs
> great with no glitches.
> 2. I have a purge script that runs via cron every half hour. It checks
> whether the hard drive is nearing full capacity. If it is, it
> automatically deletes the oldest file. This can cause the same effect
> mentioned above for 1-2 seconds.

Sounds like you are perhaps running out of IO capacity, and any cache
disruption puts the machine over the edge. As a small suggestion, you
might nice down your cron job, it might slow down the surge just enough.

Thanks for you feedback, and if you get some cpu numbers please post them.

Brian
Re: Dual Card CPU experience [ In reply to ]
On Thursday 24 April 2003 11:41 pm, you wrote:
> I wouldn't recommend anything less then a 2400+. I o/c'ed my 2400+ to
> 2.13Ghz which pushed me just over the edge to record two programs at
> 512x384 mpeg4 @ 3000bit rate, Max: 1 Min: 5 Diff: 3, and MP3 41200Hz
> encoding at 7 quality and watch one recording at the same time.
>
> The only time I notice frame drops is when another recording is just
> starting, but it doesn't happen all the time. I think if I bumped my ram
> up to 512 (from 256) it would help solve this issue.
>

Thank you for your feedback. Is your Athlon a 266 or 333 FSB version?
Sounds like your machine is striking distance of what I want.
As for ram, I have 512 in my dual 450. Where it really helps is when
one of the playback streams gets within about 2 minutes of the capture
stream, then I can see all the disk io reads stop, just like clockwork. If
its more than 1-2 minutes, then the cache isn't big enough so it has to
re-read the stream from disk. With my SCSI disks, its not the end of the
world, but my machine needs every advantage it can get; disk speed
is one of its better ones.

Again, thanks for your feedback.
Brian