[vdr] RGB/PAL over VGA at variable frame rate

Pasi Kärkkäinen pasik at iki.fi
Tue Jul 22 22:51:13 CEST 2008


On Tue, Jul 22, 2008 at 06:37:05PM +0200, Thomas Hilber wrote:
> Hi list,
> 
> the last few days I made some interesting experiences with VGA cards I
> now want to share with you.
> 
> goal
> ----
> 
> develop a budget card based VDR with PAL/RGB output and FF like output quality
> 
> problem
> -------
> 
> as we all know current VGA graphics output quality suffers from certain
> limitations. Graphics cards known so far operate at a fixed frame rate 
> not properly synchronized with the stream.
> Thus fields or even frames do often not appear the right time at the ouput. 
> Some are doubled others are lost. Finally leading to more or less jerky 
> playback.
> 

Hi and thanks for starting this project!

I'm a dxr3 user myself, but of course it would be nice to get good output
quality without "extra" hardware! :)

> 
> It appeared to be a privilege of so called full featured cards (expensive cards
> running proprietary firmware) to output true RGB PAL at variable framerate.
> Thus always providing full stream synchronicity.
> 

variable framerate.. I tend to watch interlaced PAL streams (50 hz), PAL
DVD's and NTSC DVD's.. It would be great to get perfect output for all of
these :) 

A bit off topic.. Does any of the video players for Linux switch to a
resolution/modeline with a different refresh rate when watching a movie to
get perfect synchronization and no tearing? 

An example.. your desktop might be at 70 hz refresh rate in normal use (ok,
maybe it's 60 hz nowadays with LCD displays), and when you start watching
PAL TV it would be better to have your display at 50 hz or 100 hz to get
perfect output.. and then, when you start seeing a 24 fps movie, it would be
best to have your display in 72 hz mode (3*24).. etc.

-- Pasi



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