Neo1973 video (was Re: What would be a realistic but challenging level for Bryce announced trophy money for video playback on the Neo1973? Re: h.264 format is now open?)

[Harald Welte]

On Mon, Feb 05, 2007 at 02:36:04AM +0200, Siarhei Siamashka wrote:
> On Saturday 03 February 2007 15:47, you wrote:
> 
> > Also, the 770 has a landscape display.  We have a portrait display.  The
> > S3C2410 cannot rotate the image, so you would have to rotate every frame
> > in software, too!
> 
> That's a good point. Anyway, rotation can be combined with scaling or color
> format conversion and done in a single pass, so overhead should not be too
> big. One more solution is rotation at video transcode stage as Mikko
> suggested. 
> 
> > > Just for some experiment, I compiled mplayer for arm920t (not using
> > > armv5te instructions), and benchmarked it with sdl video output (software
> > > YUV->RGB conversion, generic nonoptimized scaling 320x240 => 640x480) and
> > > libmad mp3 audio decoder.
> >
> > Please note that the LCM we use in the Neo1973 can do hardware scaling,
> > e.g. theoretically you can software-reconfigure the LCM to behave as
> > QVGA 240x320, and then change the s3c2410_fb kernel driver timings
> > accordingly.
> 
> If I understand that correctly, it is not arbitrary scaling but support for
> 240x320 resolution? 

yes, you understand correctly.

> > This has not been tested or implemented by us, since we're mainly
> > interested in getting a high-res phone UI working right now :)
> 
> I clearly understand that :) I guess it is one of the reasons, why you
> announced early access to the device for open source developers. I hope 
> that some of them would try implementing some video support.

exactly. I just wanted to make sure that this is not on our agenda, at
least with any significant priority.

> As it seems to be not quite trivial to do, this part of work can wait a bit
> until some initial video benchmarks are available (centered nonscaled
> 320x240 video playback vs. software scaled to fullscreen). 

Yes, obviously those benchmarks would help.  Anyway, the "hardware
scaling" is also interesting for non-video applicaitions such as many
old video games (ScummVM and the like).

As for the benchmarks: Obviously you consume only a quarter of memory
bandwidth when you use 320x240 than 640x480.  So native 320x240 playback
should at least theoretically be faster than centered nonscaled 320x240
on VGA.

> I'm just interested in improving video support for ARM based devices, 
> that's why I posted to this openmoko mailing list . I'm currently trying to
> integrate a fast scaler for ARM into ffmpeg library (the engine used 
> by mplayer, vlc and the other video players for linux ):
> http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-January/051209.html

good luck!  I've done some ffmpeg hacking before, and it was ...
painful... ;)

-- 
- Harald Welte <laforge at openmoko.org>          	        http://openmoko.org/
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