[linux-dvb] Re: HDTV & DVB / VDR (dscaler ..)

[Mike Pieper <mike@pieper-family.de>]

On Thursday 10 January 2002 16:17, mocm@convergence.de wrote:
> Maybe you may want to check out DirectFB, the developers were working
> on synching the v4l output to the output of the graphics card. They
> had it working for Matrox cards, but I don't know if they have other
> cards working and if it is included in the latest version.
>
> Marcus

I had a look at DirectFB and it looks really good. Right now I need only TV 
output and so I looked at the TV output quality at first. My G200 (with 
TVO-B) is not very good supported. I found some problems and was able to get 
a real good picture from this card. To process the DVB signals 
I need the extra features of this card (BES; back-end-scaler). As far as I 
understood it, I need to feed this with YUV data. Unfortunately the DVB-s 
card can deliver data only in one YUV mode due to a hardware bug in the 
SAA7146. Just this mode is not supported by the G200 card.

Yesterday I got a G400 and with this card the TV-out quality is the same as 
the G200 (Compared to the DVB-s output, it is nearly the same, but the colors 
are not so bright, but perhaps with some fine-tuning this can be made better).

I've also seen that the G400 has (from the matrox web-site) de-interlace 
support in weave and bob mode (whatever this is). On my monitor I've seen 
that there really happens some deinterlacing, as the running text on a stock 
news channel get not distorted (but was jumping from time to time). DirectFB 
is using the overlay mode to bring the picture from the DVB-s to the graphics 
card. I'm stunned that this does not produce the tearing (two pictures can be 
seen at the same time).

What I've not tested is the scaler of the matrox card. I've heard it should 
be of good quality. Anyway, when the DVB-s would be used in grab mode it is 
possible to use a software deinterlacer/scaler before sending the data to the 
graphics card. If you take a look at the dscaler software, you can see that 
they use plugins for the various deinterlace methods. These plugins often 
make usage of assembler code, but it should be possible to port these to 
Linux on the x86 architecture.

I think with all this hardware what I have now (DVB-s, Matrox G400, Sound 
Blaster 5.1) it should be possible to build a good multimedia solution or 
HTPC.

I've already written a software to display VDR's OSD on the graphics card. 
This has the same look like good old VDR (I let VDR create the image and send 
it to my directfb application instead of the DVB-card).

Now I try to integrate all the things what I've tested, to create my 
multimedia solution. I will use a master application which loads plug-ins at 
startup. 
VDR will be packed into such a plug-in. The VDR code is nearly untouched (I 
use the keyboard mode for commands; the dvbosd is patched to support a 
dfbosd).

Sorry for being so long, but it's an interesting hobby.

Mike


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