[mythtv] Memory bandwith
Monty Walls
mythtv-dev@snowman.net
Sat Jan 4 00:29:44 EST 2003
On 03 Jan 2003 19:22:12 -0500
Calvin Harrigan <calvinharrigan@earthlink.net> wrote:
[snip]
> I wouldn't say that memory bandwidth doesn't make a difference, but I
> think the problem may lay else where, processing power perhaps?
>
> The PCI bandwith is theoretically 32bits(4bytes) x 33MHz or around
> 130MBs per/s. 640x480x16bits(yuv)x30fps = 18.MBs/s. PCI should be able
> to resonably handle the tv card even if it's only getting 75 percent of
> it's maximum yield. I currently use a XP1800 with 256 megs of PC133 on
> an MSI kT133 board and it works quite well, not stuttering or any of the
> sort. I can watch live TV, record and playback simultaneously (outside
> livetv) without a hiccup.
>
> I should note that you might try increasing the PCI latency in the bios,
> it helped me some in smoothing out my system. It was not so much a
> question of bandwidth, but more of bus contention, by increasing the
> latency devices can hold the bus a bit longer to transfer data, or
> somthing like that... Getting forgetful in my old age.
The KT133 chip set max's out at about 69mb/s without the latency patches,
some raid benchmarks last year tripped over VIA pci/dma bandwidth limitations.
Doing RTjpeg, I can reduce the quality and stop the stuttering. So for my
old board it looks like a pci/latency issue.
Try using RTjpeg to the increase data-rates over the bus, instead of
mpeg4. Mpeg4 gets your pci data rates low enough that it's not a problem.
You may find stuttering under RTjpeg. At least that was my experience.
--
-Monty Walls (mwalls@castor.oktax.state.ok.us)
- MIS, Oklahoma Tax Commission
-
- My opinions are my own, my employer knows nothing about it.
More information about the mythtv-dev
mailing list