[FFmpeg-devel] PS3 Cell BE Optimizations

Reimar Döffinger Reimar.Doeffinger
Fri Oct 19 21:58:34 CEST 2007

On Fri, Oct 19, 2007 at 02:25:56PM -0500, Timothy Baldridge wrote:
> > 1. First a general playback problem, AFAIK the video driver is still
> > unaccelerated so drawing that much video at that rate is not possible.
> > This is something that will come with a driver for the Nvidia card in
> > the PS3 and it would offload CPU spent doing it in software
> I beg to differ here. 1080p @ 30fps only requires 190MB/sec of

How did you get that number? I get 237 MB/s, having hardware yuv
support would reduce that to 89 MB/s

> transfer. According to the specs on the PS3 the bandwidth to the video
> adaptor is 24GB/sec.

That certainly is an absolute maximum value (and an incredibly stupid
one combined with a claimed VRAM speed of 22.4GB/s). But even with AGP
useless extra memcpy and transfers blocking the CPU if not using DMA is
a bigger problem than bus bandwidth.

> So the only things holding you back here are 1)
> processor speed (i.e. DMA's not being used, etc.)

This seems like one critical point to me: _can_ DMA actually be used? If
not all the bandwidth won't help if the CPU can't copy the data as fast.

Reimar D?ffinger

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