[mythtv] chunky viaslice

Ivor Hewitt ivor at ivor.org
Sun Feb 22 08:58:54 EST 2004


Recently I asked on myth-users whether anyone else was seeing chunky video 
output using videoout_viaslice:- 
http://www.gossamer-threads.com/archive/MythTV_C2/Users_F11/viaslice_quality_P110009/
and it seems that I'm not totally alone in this.

Basically I'm getting odd vertical banding effects using the viaslice output 
driver with a DVB signal, the bands don't appear when the same video is 
played through another machine or another output method.

I've sort of managed to take a picture of the effect:- 
http://www.ivor.it/mythtv/dsc00916.jpg 
(Here you can see the odd vertical striping on Mel Sykes face in the Head 
and Shoulders advert! - the bronze colour of her skin seems to show up the 
problem particularly well)

I've experimented with different video modes/scaling settings, aligning the 
image to 2/4/8 pixel boundaries and so on,  but nothing seems to make any 
difference at all. The only other weird thing I've noticed is that when I 
play a 16:9 ratio picture which has been vertically letterboxed by the 
broadcaster then mpeg artifacts are visible on the extreme left and right 
of the image as new images pan into the visible area. Perhaps related.

Does anyone have any ideas what might be causing this effect? Is anyone else 
using the viaslice driver seeing this? or not seeing it?

-- 
Ivor Hewitt.
http://www.ivor.it - tech | http://www.ivor.org - hedge


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