Avermedia 771 DVB-T performance? Also how does the Mythbox scan work?
Hi,
I finished my Mythbox last night and tried to use it.. The video performance was awful. The picture and sound of live TV was breaking up, freezing, the sound popping and squesking.
THE NIGHT BEFORE THE BOX PERFORMED FLAWLESSLY!
I normally use a Freeview DVB-T settop box connected to my LCD TV. This still worked fine, even when the Mythbox was failing last night.
I have not changed anything so I am at a loss to understand why the Mythbox has become so bad.
I noticed that on both the Freeview box and the Mythbox ( setup scan), showed a slightly lower Signal strength than usual, 90% instead of 95%.
It does NOT appear to be a bandwidth / latency problem in the Mythbox. Retuning cards in the Mythbox did not improve the performance.
I tried all the various tuning tips / settings for the Mythbox, I could only make the performance worse, not better.
My new question is... How do people find the Avermedia 771 for signal performance?
Is it intolerant of low signals?
Or is it the sig to noise ratio that is bad in my box? ( If the signal is OK but the noise is high from local generated noise, this will have the same effect in clobbering the signal).
What is the "normal" operating signal to noise ratio people see when using their Myth boxes?
REGARDING the DVB-t scan system.. Is there a mechanism to optimise the signal strength?
When the box is scanning I see the screen with the sig strength and noise bars, and the statement offset / 1 offset 2 Does this get set in the database?
If so, with TWO cards, what is the correct way to set up the scans so as to ensure that BOTH cards are tuned for maximum gain?
Is ther an easy wasy to look at the card tuning entries in the Myth mySQL database?
regards
Patrick
SOLVED---SOLVED ---SOLVED It was the b****y power supply
Hi,
After 6 hours of testing I found the problem
It is an important fix as it has and will affect other people!
I did a lot of testing > 6 hours worth!!!
1. Used tzap to look at DVB-T BER and UNC error rates.
2, Found that Tzap on its own would fail all the time high unc error rate.
3. Eventually found that by removing my Geforce Nvidia 6200 PCI card and running video off the internal M/B video chip, dvb-t cards ran well no errors at all!! Mythtv and xine ran OK
4. Did a long Google for 6200 and video probs. Found a lot of similar complaints. One poster claimed fixed by changing power supply problem was fixed.
5. Found an old HUGE ATX poweer supply, slung it on top of my SilentX 250W micro atx power supply. changed over all power supply connections. Replaced Geforce nvidia 600 pci card.
6. Rebooted, checked xorg.conf was using nvidia driver.
7. SUCCESS tzap, xine Mythtv run with NO ERRORS!!!!!!!
It appears that although my power supply was not "dead", it had a degraded output and would not give enough current (5V ?) to supply the video card AND the two DVB-t cards.
Now the question is what is the best and quietest power supply I can get in micro ATX format?
Cheers
Patrick
More power supply testing
Hi,
I went to my old PC parts junk boxes and found a few more power supplies to try.
Morex Mx-450 full ATX 300W Mythtv works fine
No-Name 340 W Cheapo ATX Mythtv works fine
Expensive Silenx MATX 285 W Mythtv Fails
EverPower CWT-200MDP12(PFC) 200W Matx Mythtv Fails
All these power supplies still WORK when running Geforce 6200 and two dvb-t cards, when running LINUX, X, AIGLX, 3d rotating cubes window decorations etc, and ANY app you care to name EXCEPT any app that takes data from the DVB-t cards !!!!
BUT wait now.
I tried an ITUNER 200-m 12v-pc board. This is a miniature board that plugs directly into the motherboard power connector. It is fed from 12V DC from a hefty wall wart. The 200-M has a Total power dissipation of 200W.
This boards worked FINE!
I measured the supply current to the M-200 from the 12v wall wart. IT measured around 6.5A at 12v dc. this is ONLY 80 Watts with the Mythtv running fine recording one prog and viewing another! (all peripherals connected and working.
Unfortunately I cannot find ANY detailed specification for the Geforce 6200 and the Avermedia 771 power consumptions, especially which rails are being used.
My CPU is a mobile Athlon XP, underclocked slightly, I measured the consumption of the M/b and CPU alone as 28W !!
There is a 3.5" hdd, an idle DVD R/W unit and a PCI Wifi card to add in as well.
Can anyone point to a good reference for the power consumption figures for these cards?
I don't think there is any point looking at the OVERALL power rating of a PSU, from what I can see on the labels of the PSU's the various O/P's ( +5V +12V -12V +3.3V +5Vsb ratings vary a lot from power supply to power supply. Unless you know which rail is overloaded or noisy, then its blind luck whether a particular supply works or fails!
Lastly Just in case someone says ah but its your nvidia 6200 thats bad, I "borrowed" another one, and it fails EXACTLY the same, with certain power supplies.
Is it power limitation or NOISE?
regards
cheers
Patrick