[linux-dvb] Re: Generating progressive video

[Michael Hunold <hunold@convergence.de>]

On 02/17/04 21:05, Michael Plagge wrote:
> On Tue, 2004-02-17 at 20:53, Michael Hunold wrote:
> > On 02/17/04 15:33, Michael Plagge wrote:
> > > On Tue, 2004-02-17 at 14:35, Michael Hunold wrote:
> > > > On 02/16/04 23:38, Michael Plagge wrote:
> > > > Anyway, what solution (ie. which gfx adapter) do you have in mind to put 
> > > > the result to your beamer via DVI?
> > > Especially for this i have bought a matrox G450 with dvi-out since this
> > > is the card which seems to be supported best by DirectFB and other
> > > software using framebuffers (mplayer, xine, etc.). Therefore i want to
> > > use the matrox gfx driver.
> > Have you checked if the DVI output is actually supported?
>
> Yes, it works perfectly. I was able to use mplayer and fbtv and tvtime
> with DirectFB and/or framebuffer. I also can use a X-Server with this
> card. 
Good to hear. Does your setup work with a vertical refresh rate of 50Hz?

> To subsume this discussion, i have to do everything in software (with
> non CLE266 hardware) to get a 'high quality' solution. 
I think yes. But even on a low-end CPU (VIA C3 1Ghz, Athlon 800Mhz) you 
only need about of the 50% CPU power for pure audio + video decoding.

> I will think  a
> little bit more about my last point (using movement vectors). Could be a
> good starting point for working with mpeg2.
You would have to break up the decoding functions of libavcodec to get 
the required informations, unless you don't want to parse the whole mpeg 
stream twice. I don't say it's impossible, but you have a long way to 
go. 8-) You could write a standalone tool that simply takes a video pes 
stream, decodes and displays it -- without all the audio stuff and a/v 
sync code. This should let you concentrate on the important things.

> Do you think it would be
> interesting to add deinterlacing support to your softmpeg library, and
> is it possible to support your work on the library.
Sure. Currently, "deinterlacing" on the "local" side (ie. not on the tv 
out) is done in the sense of "stretching every field to the full frame 
size and blitting every 20ms".

I admit that this is currently more or less hardcoded for Matrox and 
cle266 and might not work for other adapters. (which aren't support by 
DirectFB anyway *sigh*)

We currently use triple buffering for video display and we don't buffer 
decoded frames. It depends on the deinterlacing algorithm if you need to 
access "older" frames, so you might need to implement decoded frame 
buffering. The current logic does "just in time" decoding, then 
memcpy()s the frame to the destination surface, then Flip()s it. This is 
efficient and work very well to achieve good av sync.

On the cle266, the tv-out is programmed to output interlaced. I can n 
confirm that it can output progressive, too, but we don't have means to 
implement and test this currently.

As you can see, "libsoftmpeg" is performing quite well, but is 
work-in-progress.

> best wishes 
> michael
CU
Michael.


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