[vdr] Epia tv-out methods (was: EPIA SP + budget hardware mpeg2/4 acceleration?)

Nicolas Huillard nhuillard at e-dition.fr
Thu Mar 10 11:21:03 CET 2005


Laurence Abbott a écrit :
> I now have an Epia MII-12000 and I'm in the process of setting it up.
> I'm assuming that others on here have tried these things so I thought
> I'd save a bit of time and share the answers with others who may be
> interested (and Google didn't really give me any straight answers!).
> 
> As I understand it, there are two methods of getting accelerated MPEG
> decoding with vdr:
> 
> 1. Using X (as described above) with a kernel DRM module and a
> (patched?) version of xfree86 or xorg. Use xine output plugin.
> 
> 2. DirectFB in conjunction with a kernel module. Use softdevice output
> plugin.
> 
> Is either of these preferable? I would have thought the second because
> there is no overhead of running X as well but the post above says that
> DirectFB wouldn't use hardware decoding. Is this still correct? Or is
> DirectFB still very flakey? From what I've seen, there are about 3
> different possible kernel modules, and the newest kernel patch I've
> found is for 2.6.8 (and I can't find a DVB kernel patch for that old a
> kernel!).
> 
> As I say, I have yet to try any of the above and was after some pointers
> before I delve into the realms of testing different options!

Your summary is good.

What I'd say (I still didn't switch back to softdevice, so I'm not 
up-to-date wrt the latest release) :
* use X / vdr-xine / XvMC when you have a regular PC (mouse, keyboard, 
etc.) : this is actually necessary to run Xine, VDR, X, etc. Xine needs 
200MB memory and X approx. 40MB (a lot is shared, and works with 256MB 
RAM). Add that to the 40MB for VDR...
* use softdevice / DirectFB / software decoding if you have a STB-like 
HTPC (no keyboard, no mouse, just the remote) : runvdr will handle 
running VDR *and* the display, restarting, etc. Software decoding is not 
a problem for your 1.2GHz processor (indeed, less a problem than running 
Xine separately)

Subscribe to the softdevice mailing-list (softdevice-devel at berlios.de). 
There are interesting developments and skilled developers there.

The subject of you post mentions "tv-out" : this is a great subject, and 
you should really consider the output quality in your planning.
The TV-encoder on the EPIA board (VT162x) is driven by data tables, 
present in the frame-buffer kernel module for the CLE266, and also 
present in the X driver for the CLE266. These tables contains many 
parameters for the video output (PAL, NTSC, anti-flicker, etc.), and 
come from VIA. The parameters are actually far less than optimal (in the 
  versions I have, dated a few months back) : the image has large black 
borders around (each 4 sides), is largely anti-flickered, thus blurred, etc.
This lead to a huge loss in resolution. 720x576 should be full PAL 
display, but is actually far less with these tables. Ville Syrjälä from 
the DirectFB ML sent me the doc for the VT162x encoders, but I don't 
have time to dig into better parameters. I can send it if anyone want to 
improve that.
The alternate TV-out method is to generate SCART RVB signal from the VGA 
output of the board, which should be good, if one can find the correct 
timing for the frame-buffer driver and/or X driver.

-- 
NH



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