Video Playback virtually impossible on Neo Freerunner? (Re: Video of Qt 4.4 on Neo1973: brings iPhone like graphics)

[Carsten Haitzler (The Rasterman)]

On Tue, 29 Apr 2008 00:12:32 +0200 wim.delvaux at adaptiveplanet.com babbled:

> On Monday 28 April 2008 17:40:38 Carsten Haitzler wrote:
> > On Mon, 28 Apr 2008 09:26:43 -0500 "Tim Shannon"
> > <shannon.timothy at gmail.com>
> >
> > babbled:
> > > But isn't it still limited by the bandwidth available from the micro SD
> > > card?  Maybe I misunderstood that.
> > >
> > > Basically what I'm curious about is if in the future someone does take
> > > the time to figure out and write the appropriate driver for the glamo
> > > chip, will we be able to watch movies on the free runner?
> >
> > please follow the thread. it *IS* possible. you just need to give up
> > something. resolution or framerate. simple as that. the glamo has limits
> > like any piece of hardware. they are just not very "extreme" limits. they
> > are rather narrow.
> 
> Euh, I thought that is it because the glamo and the SD are on the same 'bus' 
> or something that there is a bottleneck, not because of the glamo.
> 
> Or am I missing something ?

read back. there is a bus between the cpu/system memory and the glamo. this
busy is used to:

1. transfer graphics data to and from the video card (glamo)
2. transfer SD IO data to and from the micro-SD card

this bus has a limit of about 7.3m/s.

to give you an idea of graphics data, 1 RGB565 image @ fullscreen VGA is 600k.
you do the math. when you decode a video file it is decoded with the cpu in
system ram. the file is read from somewhere (SD card, network, internal flash)
which consumes IO bandwidth approximately according to the actual file size (1
minute video, if it is 60mb in size means you consume 1m/s of IO bandwidth,
ignoring caching - as cacheing for such large files will be mostly useless).

you then need to consume cpu cycles (and memory bandwidth) to decode that video
to its native colorspace of YUV (this is not RGB). YUV as used by most video
formats uses less space than RGB565 (25% less) so 1 fullscreen VGA frame of
video data is 450k. in order for this to be displayed it HAS to be transferred
to the video card - across the bus. every amount of time spent copying data
to/from the glamo is time that cannot be spent doing something else as the cpu
is waiting on the glamo bus.

> W
> 
> >
> > > On Mon, Apr 28, 2008 at 7:12 AM, Mikko Rauhala <mjrauhal at cc.helsinki.fi>
> > >
> > > wrote:
> > > > On ma, 2008-04-28 at 13:59 +0200, wim.delvaux at adaptiveplanet.com wrote:
> > > > > What if you could use one of those 'coming very soon' Laser
> > > > > projection device(s) connected to USB ?
> > > >
> > > > You'd be looking at 12 Mbit/s max for the USB1.1, not fun.
> > > >
> > > > Really peeps, face it, seems that the sane way to do non-crappy video
> > > > on the Freerunner is to get driver support for that Glamo mpeg-4
> > > > decoding (remember, the hardware is capable). Hopefully everyone's
> > > > grasping at straws makes OM bump up the priority a bit (though again,
> > > > for now there are certainly more important things to do).
> > > >
> > > > --
> > > > Mikko Rauhala   - mjr at iki.fi     - <URL:http://www.iki.fi/mjr/>
> > > > Transhumanist   - WTA member     - <URL:http://www.transhumanism.org/>
> > > > Singularitarian - SIAI supporter - <URL:http://www.singinst.org/>
> > > >
> > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > Openmoko community mailing list
> > > > community at lists.openmoko.org
> > > > http://lists.openmoko.org/mailman/listinfo/community
> 
> 
> 
> _______________________________________________
> Openmoko community mailing list
> community at lists.openmoko.org
> http://lists.openmoko.org/mailman/listinfo/community


-- 
Carsten Haitzler (The Rasterman) <raster at openmoko.org>