this is on linux. when I play certain films on the TV-OUT I get a sort of white flicker line that rolls down semi-fast. It definately is linked to HD access since when itaccesses it more then I get a lot of them and almost none when playing CD (swaps very very little then)

What could this be? Not enough power? Too much CPU taken? :confused:
Posted on 2003-03-11 05:09:28 by Hiroshimator
most likely too little power the CPU is no doubt running full tilt ( drawing the gratest power that it will draw) the hard drive pulls more power than any thing eles in a computer and peeks on head movement

or may be the system buss is too slow for the demand at that time

did you try it in single user mode ( may be the system buss and CPU cant keep up
with the display and hard drive ) litghten the load

may be a memory upgrade will fix this (single user mode will at least give an indacation of wether or not the problem is low ram)

what dose top or xload have to say about whats going on with memory and CPU useage may be you could renice what ever you are useing to view the move
Posted on 2003-03-11 10:50:31 by rob.rice

this is on linux. when I play certain films on the TV-OUT I get a sort of white flicker line that rolls down semi-fast. It definately is linked to HD access since when itaccesses it more then I get a lot of them and almost none when playing CD (swaps very very little then)

What could this be? Not enough power? Too much CPU taken? :confused:


What does

# hdparm /dev/hdX

tell you?
Posted on 2003-03-11 11:11:35 by bazik


multcount = 32 (on)
IO_support = 0 (default 16-bit)
unmaskirq = 0 (off)
using_dma = 1 (on)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 8 (on)
geometry = 1048/255/63, sectors = 16841664, start = 0


:|
Posted on 2003-03-11 12:07:49 by Hiroshimator
Do you have a Nvidia/ATI graphic card and if yes do you use the vendor drivers?
Posted on 2003-03-11 12:23:12 by bazik
yep, using nvidia drivers and also nvtv driver

works very well

the card itself is a TNT2
Posted on 2003-03-11 12:28:23 by Hiroshimator
Very strange :/

Did you ask in irc if someone has a similar problem?

How much is the CPU load when the flickering happens? Do you touch swap when it does?
Posted on 2003-03-11 12:32:00 by bazik
yes it seems to just touch swap then (max swap usage I've seen until now was about 50MB) . This really happens only when it uses the HD.

the system itself is a celeron 500 with 128MB RAM

maybe it's just insuffici?nt?
Posted on 2003-03-11 12:33:04 by Hiroshimator

yes it seems to just touch swap then (max swap usage I've seen until now was about 50MB) . This really happens only when it uses the HD.

the system itself is a celeron 500 with 128MB RAM

maybe it's just insuffici?nt?


Yep, maybe. Did you try to increase the RAM?
Posted on 2003-03-11 12:37:06 by bazik
don't have any ATM

I'll take some out of my main box later and try :/

but even then it's weird. Maybe it's the CPU being too slow.
Posted on 2003-03-11 12:46:49 by Hiroshimator
Do the HDD cables run anywhere near the card too?

It could be EMI from the cables affecting the signal to the TV...
Its unlikely though...

Mirno
Posted on 2003-03-11 13:01:54 by Mirno
that would cause a steady distortion no?

it's really when I hear it(the hd) ticking that the most stripes occur.
Posted on 2003-03-11 13:11:14 by Hiroshimator
My guess is its your Power Supply and your Hardrive (and probably everything else in your system that gobbles power).

Those white lines are from voltage distortions on supply rails (5v dc) which your video card uses. Eveytime your HD grunts, a more significant motor is drawing inrush of current (think of it like water-hammer in your plumming). There is a bit of a "kick" to the entire system when it suddendly start/stops. This makes the voltage "distort" a little on the supply rails (that are equally distributed throughout your CPU ~ just like bathroom pipes in an appartment building).

This distortion recovers very quickly, however, your TV signals are producing 350 pulse trains of info to make one 'screen', 50 times a second. (thats alot of pulses). So a fast distortion on the rails, will be noticeable in 2-5 pulses. The effect is they diminish in quality in contrast to the other pulses that have quality. This is why you can distinctly see lines on the screen.


So how to fix this, or even test my crazy theory. Lighten up the loading on you power supply if you can, and then give it a test. Unplug other CD roms, and fans (temporarily) and see if it helps. If so you need a more powerful powersupply.

I would also check the power consumption on your hard drive(s). Some of them can be real pigs with power. Another solution is to replace the HD with a more modern one.

Anywho, this is the problem as i see it. There are a few other things you can do, but they really require more knowledge of electronics.
:alright:
NaN
Posted on 2003-03-11 23:57:33 by NaN
To kill some miss-conceptions:

1) EMI is caused by a rappid change in voltage/current in a very short period of time. EMI radiation dissipates by 1/r^2. So a big factor in spreading EMI noise is the source voltage that is being switched. A 120V light dimmer 'chops' the sine wave at irregular phases. This creates ALOT of EMI when the choping is near 90 degrees (120V cos ( 85 ) ~ = 120v) . The thing about computers is it has 5 Volts, to run all digital devices. Digital implies alot of sharp voltage changes from 0-5volts. However, the amount of loading is soo insugnificant its not a problem.

If it were, your 900Mhz cordless phone would go on the fritz when you get near your 1Ghz CPU.

So EMI is not a very likely source of your problems.

If you were concerned, you can protect your wire by shielding it from EMI. This is done by wrapping the wire in a conduit (conductive), and grounding it at one end.


2) TV output is an analog signal and at a very low voltage ( under 3 V dc ). The gradiants between colors is represented by changes of approximately 0.01 V to the analog sinal. "pixels" are aligned with TIME (analog value at time 'x' in a pulse train). The analog values are created by a Digital -> Analog converter. And the digial info comes from your memory (most likely Direct Memory Access (DMA) ~ which bypasses the CPU). So your CPU 'loading' is not likely to be an issue either.

3) The only left over is Power. Which is explained above. However, thinking a bit harder, there is other ways the power 'noise' can make its way onto your screen. If your power supply is a piece-o-crap and has no filters, noise can make its way back to the 120v plug you power your CPU with. If your TV is on the same outlet, you can 'water hammer' the TV rather than your signal. This is a very unlikely scenario since Hard-drives dont consume THAT much power. However a good example of this is when someone turns on a BLENDER while your watching TV. (you get static all over the picture ~ since a blender is a moderately large 120V motor drawing a good load, and having its power chopped by the ROTOR as it turns (repeated 'water hammering' effect which also spews out EMI around the blender).

More fun facts...
:alright:
NaN
Posted on 2003-03-12 00:19:43 by NaN
it's an older HD, probably the cause of the problems :/

as far as plugging things out: that would be a CD-drive and a NIC I could plug out, there is nothing more in the box :)
(so I don't think that would help)
Posted on 2003-03-12 04:29:58 by Hiroshimator

it's an older HD, probably the cause of the problems :/


Whats the (theoretical) speed of the HD? (hdparm -tT /dev/hdX)
Posted on 2003-03-12 08:43:13 by bazik