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| Poor scaling performance http://forum.linhes.org/viewtopic.php?f=15&t=10297 |
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| Author: | nigelpearson [ Thu Jun 01, 2006 6:06 am ] |
| Post subject: | Poor scaling performance |
Today, I finally decided to spend the time to improve my picture quality, and I thought others might be able to learn from my mistakes. * Watching SD content in Australia. 720x576, 50 interlaced frames/sec, from either DVB-T or DVD, between 5 and 11Mbit/sec. Most of it is 16:9. * My "early 2005" setup was motherboard internal VIA chipset (KM400) driving a 1024x768 projector. This is a good match for 576line material, becase only horizontal scaling is needed (1024 / 16:9 = 576). * I eventually upgraded to a 720p widescreen projector. Sadly, it wouldn't scale XGA to the full panel size, so I had to change the XF86Config. And, because the KM400 won't do 1280x720 with the current X drivers, I had to compromise at 1280x768, which the projector scaled down to about 1200x700. This resulted in a very soft image in both the MythTV UI and Xv scaled material. * Today, I installed a cheap NVidia card: Code: $ cat /proc/driver/nvidia/cards/0 KnoppMyth autodetected it and loaded the kernel module, and after some tweaking of the config, I had perfect 1:1 mapping between X and MythTV, and the projector.
Model: RIVA TNT2 Model 64/Model 64 Pro IRQ: 21 Video BIOS: 02.05.17.03.00 Card Type: AGP Now, this gives me a perfectly sharp MythTV UI, but the problem is the Xv-scaled material. Both DVB-T material in MythTV, and DVDs viewed in Xine, have a scaling artifact. It is most noticeable on the OSD text, where the white text has some grey lines in it. It is like there is some hard "ringing" in the scaling. So, I have gone from a soft scaled picture to some hard noise. Has anyone else noticed anything like this? I am hoping that a better card (I will try an FX5200 tomorrow) may help. |
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| Author: | nigelpearson [ Thu Jun 01, 2006 9:48 pm ] |
| Post subject: | |
As expected, a better video card removed the scaling artifact, and decreased CPU load (I assume because it went from AGP4X to 8X). Still not perfect, though. At 75Hz refresh rate, there is occasionally some tearing, and after about an hour of watching HD TV, the sync started misbehaving on the card. Taking the top back off the PC helped a bit, so I suspect I need more cooling aroung the FX5200's non-fan-cooled heatsink. But, at least I have 1:1 mapping, and a sharp image in both the Myth UI and in watched material. |
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