[vdr] vdr on PS3

Matthias Schniedermeyer ms at citd.de
Fri Jan 5 00:31:27 CET 2007


Pasi Juppo wrote:
> Matthias Schniedermeyer wrote:
> 
>>Clemens Kirchgatterer wrote:
>>
>>>Matthias Schniedermeyer <ms at citd.de> wrote:
>>>
>>>
>>>>I'd say the only downside of the Linux support kills it as a VDR
>>>>platform. Graphic is NOT accelerated.
>>>>
>>>>That's the only downside i'm aware of, and i can understand Sony a
>>>>little in this point. Otherwise all game developers could just skip
>>>>paying licensing royalties and just develop for Linux at PS3.
>>>
>>>but why should this matter for multimedia (video) applications? ok, we
>>>(most likely) don't have hardware accelerated xvmc, but 6 vector cores
>>>to do it in software.
>>
>>Video is inherently bandwith intensive.
>>At least (for PAL):
>>720x576x4x25 = about 40MB/s (*)
>>1920x1080x4x25 = about 200MB/s
>>
>>And that's taking aside ANY of the other processing. Decoding, IDCT,
>>YUV->RGB transformation and so on. Also taking aside the total bandwith
>>killer, when you have to scale the material.
>>
>>AFAICT the vector cores COULD(*2) help you with the first parts, but the
>>rest has to be done by the 3(,?)Ghz RISC PPC-CPU and shoveling that much
>>data back and forth may be a bit much, without any acceleration.
>>But on the other side the PS3 systems is supposed to have an impressing
>>memory-bandwith, which could rescue the day.
>>
>>So unless someone tries there is no way to be sure, but for the time
>>beeing i'm sceptical.
>>
>>IOW:
>>- SDTV maybe
>>- HDTV no way without acceleration
>>
>>*:
>>x4 isn't a typo. Most systems use 32 bit per color. 24 bit "packed"
>>format isn't used anymore AFAIK.
>>
>>*2:
>>If you have software that can use the SPUs, but unless someone writes a
>>Decoder-Library with SPU support you can only use the Main-CPU.
> 
> 
> I hardly believe that PS3 would suffer at all when doing HDTV without
> acceleration. There was a test several months ago of the cell processor.
> It handled 48 SDTV MPEG2 streams in real time and displayed, thus scaled
> down, them all at the same time on HDTV screen. I don't think hardware
> acceleration is needed for x264 HDTV decoding. Only problem is the DRM
> part and of course BR disc playing under Linux.

I just tried playing back a Mpeg4 AVC HDTV (1900x1080) video(*) with
xine -V xshm
That sould be pretty much unaccelerated.
My system (CORE 2 Duo E6700, or about the fastest "not extreme" CPU you
can currently buy, sided by 2GB DDR2-800 RAM and a Geforce 7600GT) does
that with about 90% CPU for the xine task and 9% for X. IOW it pretty
much sucks up all power from one of the two cores.

So i revise my guess.
The PS3 may still be able to play back a Full HDTV stream. Maybe even a
decoder just using Altivec optimizion provides enough raw horsepower to
do the job. (IIRC the PowerPC-CPU of the PS3 has Altivec.)
If not, offloading just enough of the processing to the SPUs to have
enough horsepowers left for the rest may be the way to go for a
"PS3-Media-Center".


*:
http://www.apple.com/quicktime/guide/hd
I used the
http://www.apple.com/quicktime/guide/hd/bbcmotiongalleryreel.html


Bis denn

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