[mythtv] MythTV does not appear to work with FB setups

Richard Jones mythtv-dev@snowman.net
31 Aug 2002 22:18:41 +1000

On Sat, 2002-08-31 at 18:07, Preston A. Elder wrote:
> Heh, I use the fbdev X driver (which uses the kernel vesafb driver).  I am 
> already in X, and quite nicely (1280x1024x16), but right now, my vid card is 
> not supported natively by X (its a Matrox Parhelia, and Matrox hasnt released 
> their native driver for it yet). This means I'm relegated to using either the 
> vesa, or the framebuffer driver.  The vesa driver screws up the console when 
> I return to it from X, so I went with the framebuffer device.  It works well, 
> however xvinfo tells me I dont have a vid card.

xvinfo is not telling you that there is no vid card, it is saying that
your video card does not have any Xv (Xvideo) extensions. Xvideo is an X
extension which provides a layer to deal with things commonly done when
working with video such as overlays, scaling, colour conversion etc.  To
do this the driver for your card must support these activities.  You do
not have a driver that supports these features. When matrox produces a
driver for your card you will *probably* have these features. Matrox
have produced open source drivers for previous cards, however they have
not provide source code (or specifications) for their TV-out chips. In
fact they have not supported TV-out even in binary form in any card
after the g400.  There are a few bits of code around to provide
solutions for TV-OUT on more recent matrox cards, but there are usually
tradeoffs with these solutions as they have been done by reverse
engineering the tv-out chip and lots of the registers involved are still
a mystery. ATI cards are in a similary situation, ATI will not realease
TV-OUT specifications and reverse engineering is a long and error prone
process.  NVidia appear to have decent binary only drivers for tv-out
but the quality of the output is said to be not up to what can be
achieved on the Matrox and ATI cards.

[ SNIP ]
> Aparently the framebuffer support tho, does not support the XVideo extension 
> (I'm not sure if the 'vesa' driver does tho, that might be enough to make me 
> say 'damn the console, I'll use the vesa driver' if it supports XV 
> extensions, does anyone know if it does?).

No it doesn't.  There are a few solutions to your problem. 
1) Get a better supported card is probably the easiest. Given that
you've purchased a Parhelia, I figure money probably isn't an object ;-)

2) Either write yourself or beg someone else to write fallback code for
MythTV which provides software replacement code for the Xv hardware
accelated features where Xv is not available. You'll need a faster CPU
to achieve the same quality results an Xv supported card would get if
you go this direction.

3) Wait for matrox to release drivers and hope that Xv (and Tv-OUT is

4) Write drivers for your Parhelia.  

In terms of 2) I'm considering adding DirectFB support to mythtv
(DirectFB has some tv-out stuff for the g400 (my card) that none of the
other g400 tv-out solutions have right now). DirectFB support would
allow mythtv to work with any card support by a framebuffer device
(including vesafb). I've just started thinking about this and I'm not
sure it will match in well with mythtv, but if it does don't expect
anything in the very near future on this.