[K12OSN] Pixelation with MPlayer

"Terrell Prudé Jr." microman at cmosnetworks.com
Mon Mar 5 18:35:53 UTC 2007

James P. Kinney III wrote:
> On Sun, 2007-03-04 at 22:41 -0500, "Terrell Prudé Jr." wrote:
>> Try upgrading your video card.  The problem that you're discussing has
>> nothing to do with CPU, but rather is a video card speed issue.  I
>> replaced an ancient S3 Trio64 with a Matrox Millenium G400, and my
>> issues with slow video playback went away.  The thin client is a
>> Pentium II-300MHz.  My server is a dual Athlon MP 1.2GHz with 2GB
>> DRAM.  Now, unless you're trying to run a LTSP *server* on a Pentium
>> II-300MHz  or something else ridiculous like that, CPU ain't your
>> problem, dude.
> Upgrading the video card is not an option since these are brand new HP
> T5125 thin clients and I deployed 2200 of them. The process of viewing
> video clips using thin clients requires that the server do the heavy
> lifting, not the client. For the same reason than 3D-accelerated
> graphics won't work in a thin -client setup, neither will using the
> graphics card to do the video decompression.

That sounds like a video driver issue, actually.  I have 3D accelerated
video working just fine on my thin clients.  But I've also got a video
chipset that is very well supported by X11.  This is a big factor; I
tried a modern nVidia card in that same thin client, and things got
D-A-W-G slow.  You're partly right; the client's CPU doesn't do any
heavy lifting.  But the client's *video board* does in certain cases.

> The servers - all 24 application/boot servers - are dual CPU/dual core
> Opteron 1.8GHz w/ 8 GB RAM and 6 Gb NICs with 4 bonded for data pipe to
> the thin clients are all connected with 1000BT networking down to the
> gig switch in each classroom. The clients are the only thing running
> slower.
> I have an average of 90 clients per server. In actuality, I have one
> with 123 clients and a couple with 110. 

My God...are all of these 90 clients/server streaming video simultaneously??

On my dual Athlon 1.2GHz, I show a 640x480 MPEG4 session taking up 21%
of one CPU (no frame drops).  So, I think I could reasonably get away
with 8--maybe 9, but that's pushing it--sessions at that resolution
using both of my CPU's.  Another MPEG4 clip at 320x240 used up 7% (the
HOSEF clip on K12LTSP from last year), so I could do a lot more--maybe
13 per CPU, or 26 total simultaneous--at that resolution.

Your network bandwidth does seem to be fine if your bonding four Gig-E
NICs;  at 45Mbps per session, you can get away with 88 simultaneous
streams of that size before the network becomes a bottleneck.  That
assumes that nothing else is crossing that pipe at the same time, of
course (thick clients using the K12LTSP server as a router, etc.).  So,
for streaming locally from the K12LTSP server, and assuming that there
are no errors (faulty cable, dirty connection, etc.), the LTSP LAN looks

If you're not streaming locally, i. e. you're doing it from the
Internet, then have you made sure that you have a sufficiently large
pipe to the Internet for however many sessions that you're streaming at
once?  We ran into that problem with United Streaming and had to install
"cache" servers.  Each of our "cache" servers goes and downloads the
videos from United Streaming at night, storing them on their (very
large) RAID 5 arrays.  Then, when our teachers want to play United
Streaming videos in class, they get redirected via policy routing to our
cache server bank, thus saving our Internet pipe.

>> Please stop the FUD and ask questions before you go spouting off
>> erroneous conclusions,
> Not to sound like I'm biting your head off for the FUD statement, but I
> have tested this and found that it simply isn't a workable process to
> use thin clients _reliably_ to watch video clips. The synch between
> sound and video gets off pretty quick depending on server load, the
> video is halting and pixilated. 
> I have not been replying much for the past 6 months on this list as I've
> been a bit busy installing those 220 clients and 24 servers here in
> Atlanta.

That is great that you're installing all those, and I wish that my own
district would be open-minded enough to try it.  We could use some
Atlanta common-sense in that way here where I live.

But I must re-interate:  I've gotten video to work just fine on LTSP
clients, and it wasn't that hard.  If you've got 90 clients/server
streaming video simultaneously, try breaking that up some among more
servers.  That's a heavy load, even with two dual-core Opterons per server.

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