Converting to HD-SDI

[samsc]

noone seems to have asked the fundamental questions with video input ....

so i need to ask them-

what camera source ntsc or PAL?

what refresh rate and frame rate are you running the screens at?

what frame rate is catalyst set to playback at?

I should be more clear.. sorry.. its not the delay.. I find it very acceptable for what we do. What I am experiencing is dropped frames resulting in jerkiness etc. It will happen for a few seconds out of every minute and then clear up. For instance.. If I am using 2 lfg cards, of the eight inputs at any one time there is likely one that will briefly have some frame loss... it will clear up and then reappear elsewhere within a short time. This happens with or without any other playback load on the machine. The GPU usage is minimal also... it seems to be a buffer issue similar to the problems with the later generation od Black Magic hd extreme cards if that helps describe it any.

[ajmaudio]

Thanks for the continued support Richard.
The cameras are all professional and are going through GV DAs.
The LED is Barco SLIGHT with LED PRO controllers running DVI from Cat to Led Pro

I'll try what you suggest as soon as I can. Could be a bit before I get to try this. Wish this was not the case. It seems like this would fix it. Any other thoughts on this subject?

[ajmaudio]

on a side note... if you wanted to take the time to explain precisely how that few seconds of jittery video happens I would love to hear it from you Richard. The concept is simple enough however I am curious as to what happens with the buffers or whatever it is at that precise time. Understanding is power

[samsc]

on a side note... if you wanted to take the time to explain precisely how that few seconds of jittery video happens I would love to hear it from you Richard. The concept is simple enough however I am curious as to what happens with the buffers or whatever it is at that precise time. Understanding is power

first of all we need to do some experiments by changing some settings-
there are many different possibilities - sometimes unexpected -

in this situation there isnt usually a technically correct answer -
we have to try to find the best visual solution by changing graphics card settings and catalyst playback rates-

I made these settings available because these situations arise a lot.
and we have to find the best solutions-

i have a lot of situations where the timecode is 25Hz- but the screens only run at 60Hz- for example with element labs controllers used in europe-

sometime the client has to sync to external source without timecode available and the external source runs a little fast or a little slow-

sometimes the frame rates - screen outputs and timecode are all mixed up and cannot be changed...

sometimes projectors really dont like working at 75Hz- only work at 60Hz - but show is at 25FPS... eurovision 2004

i had a show last year with martin lc panels- and they took really strange input rates- i cant remember exactly- but completely non-standard - and the show was run from a laptop- and laptops have refresh rates you cannot change....
and on and on...

----

a very quick technical metaphor is this-

you have 2 conveyor belts running side by side- they have fixed bucket positions- they are not continuous belts- one can transport 899 cabbages per minute- and the other runs slightly faster at 900 cabbages per minute-
how do you get the cabbages from one conveyor belt to the other?
what happens if you cannot exactly or precisely measure the positions of the cabbages?
what happens if the rate of the conveyors changes slightly all the time?
or the positon has some mechanical hysteresis in it?

[samsc]

on a side note... if you wanted to take the time to explain precisely how that few seconds of jittery video happens I would love to hear it from you Richard. The concept is simple enough however I am curious as to what happens with the buffers or whatever it is at that precise time. Understanding is power

another really really common thing-

is that people run multiple monitors out of a computer at different sizes and refresh rates-
sometimes they run a triple head and a single screen-

with this - the refresh rates are different to each monitor

vga/dvi have different refresh rates at different sizes-

for 60Hz its somewhere between 60.04 and 59.95

dvi and vga are not constant frame rates at different screen sizes.

then they do video input - at 25 or 29.97 -

an enormous number of possibilities - i try to do the best possible thing for these complex scenarios.

i found a vga frame rate calculator at :
http://www.tkk.fi/Misc/Electronics/f...2rgb/calc.html

[ajmaudio]

I get the metaphor.. I guess I was looking for more of a precise explanation of what happens in that jittery moment as far as the machine itself....why does it work fine, then jitter, then work fine again. its liek the cabbages line up for a bit then don't... or there is a buffer in there helping out that can only help sooo much or sumthin. Guess I am not explaining myself well. I get that they are different rates and all. I guess I figure if anything this would cause it not to work at all... not the work90 percent of the time.. then not.. then work again thing.

[samsc]

I get the metaphor.. I guess I was looking for more of a precise explanation of what happens in that jittery moment as far as the machine itself....why does it work fine, then jitter, then work fine again. its liek the cabbages line up for a bit then don't... or there is a buffer in there helping out that can only help sooo much or sumthin. Guess I am not explaining myself well. I get that they are different rates and all. I guess I figure if anything this would cause it not to work at all... not the work90 percent of the time.. then not.. then work again thing.

'jitter' isnt a sign of it not working -

its one of two things- 2 frames of video falling within a single screen refresh - or 2 screen refreshes within a single video input-

what happens with buffers - they add a delay- and then people complain about latency... but there are several buffers -

i give access to the buffer settings with frame rate settings- and you can make slight adjustments with these things to compensate for frame things-

you need to try different frame rate settings and see what happens.

[ajmaudio]

thank you for that explanation... makes sense. is it normal for this to occur for several seconds then clear up?