[MPlayer-dev-eng] DMA or not DMA

Arpi arpi at mplayerhq.hu
Wed Jan 5 23:04:08 CET 2005


any news on this? (implementing DMA support for mga_vid)
my sponsor is interested if we can do it soon (in 2-3 weeks)
or they have to find different solution...

if anybody interested implementing this, tell me.
also tell me (in public or private) how much money it costs...
so i can pass it to the sponsor.

> On Wed, 24 Nov 2004 15:37:17 -0300
> Daniel Serpell <daniel_serpell at yahoo.com> wrote:
> > > btw, is it possible at all to run multiple dma transfers (to
> > > different cards) in the same time? or bus-mastering is about it?
> > > (ie only one dma transfer over pci bus)
> You can set up multiple dma transferes w/o problem, as long as
> the dma controller has free channels. Of course, only one transfere
> at a time is possible unless you have multiple independent busses.
> I dunno how linux handles this, but i guess that linux keeps
> it's own buffer for pending dma transferes and processes one
> after each other (at least, that would be what i do)
> > There should be only one bus-master on the bus at any given time,
> > so there is bus-arbitration going on. Normally, each bus-master
> > transfer takes at least about 16 words (ie, 64 bytes in PCI-32)
> > and then the bus is released. The "latency-timers" on each PCI
> > card give the bus information about when a master should release
> > the bus.
> Latency is of no concern in this case as you want to show all
> frames at the same time. Additionaly it's actualy better to
> keep the transferese together to skip the setup phase
>  			Attila Kinali
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A'rpi / MPlayer, Astral & ESP-team

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