[mythtv] Memory bandwith

[Calvin Harrigan]

On Fri, 2003-01-03 at 19:29, Monty Walls wrote:
> 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.
> 
> 
> 
> 
I tried both rtjpeg and mpeg4, both work well but I get better quality
with mpeg4.  I haven't had a problem with stuttering since I got my
hardrive running in udma mode.

Calvin...