[mythtv] [mythtv-commits] Ticket #5643: Match refreshrate with input framerate to reduce judder.

[Jean-Yves Avenard]

Hi

2009/7/5 John <reidjr at btconnect.com>:
> This is great. Perhaps your "ideally" answers my question. I was going to
> ask if there was anyway to frequency match when using S-Video output from an
> NVIDIA card.  My TV is happy to take 25 and 30 Frames interlaced over
> Svideo. but I can only achieve this by changing the svideo settings in Xorg
> from PAL to NTSC and restarting.

The current patch ignore the refresh rates marked as "Interlaced"
using the NV-EXTENSION and Dynamic Twinview. There are several reasons
as to why this decision was taken...
For a start, currently DisplayRes (the class handling the screens)
isn't interlaced aware; all it knows is the resolution of the screen,
the refresh rate and the aspect ratio; prior to this patch, the
refresh rate was completely independant of the rest of mythtv.
Because of this, for displayres, a 50Hz progressive screen appear just
the same as a 50Hz interlaced screen and there's no way to make choice
as to which one is best.
It will also give priority to progressive screen configuration because
that's the most common these days.

Currently, Myth will only ignore the screen resolution marked as
interlaced if you are using Dynamic Twinview. It's currently the only
mechanism reporting if something is interlaced or not, otherwise Myth
uses XrandR to know about what the screens are, and this doesn't tell
if a screen is interlaced or not (as far as I'm aware, I may be wrong)

But there are still ways to get what you want to achieve with this
current patch...
But not having enough information about your particular setup mean I
can't provide a direct answer.

In any case, Myth can only switch between the refresh rates it knows
about. If your video card only reports one rate at a time without
changing the X configuration, that's all myth can use.

When you run xrandr, what refresh rates does it report ?
With Dynamic TwinView active and inactive?

When you run nvidia-settings, what refresh rates does it report ?

If you download the source code of nvidia-settings
(http://cgit.freedesktop.org/~aplattner/nvidia-settings) , there is a
"sample" directory.
Compile the program nv-control-dpy with the option:
--print-used-modelines

This will show all the modelines currently usable by your videocard/screen.

This will allow to tell me weither mythtv with the patch will be able
to switch between the video mode properly...

If only one rate is reported, you will have to fiddle with xorg.conf
and add the require modelines so X is aware of the modes available.

At the end of the day, mythtv can only work with the information it has.

This conversation is probably better suited either directly to me, or
the mythtv user group rather than the development list ... I'm sure
none of the other developers are interested.

Jean-Yves