[mythtv] Memory bandwith

[Monty Walls]

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.