50hz

[Sven]

My Projectors (put simply) do not seem to like 75Hz very much, which I am told is a known bug. The content is all 25fps. At the risk of exposing my ingnorance, I am interested to find out why I cannot run a display at 50Hz in Catalyst?

Thanks.

Sven

[samsc]

i cannot switch my displays in the 'Displays' preferences to run at 50hz.

can you?

[Sven]

No.The question is, why can't I?
As it turns out the Barcos I am using prefer multiples of 30Hz, so I am barking up the wrong tree anyway by wanting to change the frequency to 50Hz. Never mind.

[samsc]

monitors tell the computer which resolutions they support.

sometimes.
most of the time, they should.

And then there are the graphics drivers.

Somewhere in the OS some piece of software is deciding that the monitor output cannot be run at 50Hz, this is beyond my control.

--
50Hz refresh on a CRT would flicker terribly.
But on an LCD it might just be acceptable.
--
You can run the TV ( svideo ) output at 50Hz.
But this isnt any good for you as I think you are using a high resolution output 1280x1024?

[samsc]

No.The question is, why can't I?
As it turns out the Barcos I am using prefer multiples of 30Hz, so I am barking up the wrong tree anyway by wanting to change the frequency to 50Hz. Never mind.

Projectors have their own native refresh rate --- which complicates the entire thing.

Sometimes monitors will convert what they receive to a common rate which works with the DLP chips.

Are you using a DLP projector?

(DL1's also dont like working at 75hz - when you strobe them fast (black/white ) - you will notice banding in the image - but for most content this is OK )

[samsc]

If you change to 60Hz/30fps, please note there is a bug in the OS which requires the installation of the ATI displays software, and the manual setting of a 'performance setting'

Please see:

http://chaldee1.gotadsl.co.uk/~richardb/upload/showthread.php?t=448

[samsc]

you cant really switch to 60hz can you?
all your content would speed up?

and you are using hidef stuff, so the performance probably wouldnt be enough?

[tharding]

Which Barco projector are you using?

Another solution is to put a scan converter inline like a Sony 1024 or Extron USP405. with these you should be able to output at whatever frequency you like.

Cheers

Toby

[Mr_P]

Think this 75Hz issue is a BIG problem...

especially as a number of reputable hire companies with lots of DLP's end up having to use them at 75Hz because there's no other option with catalyst...

(unless we all use NTSC footage and switch to 30Hz and multiples therof...)

So whats the solution?

[samsc]

But isnt the issue that the DLP projectors dont like 25 or 50 or 75?

That they work better at 60hz???


----

you dont have to use 'ntsc' footage in catalyst
switching to 30hz, just speeds up the playback.

you dont have to make a single change to the content.
pal content will playback at 30fps thats all that will happen.

[tharding]

I use Barco DLP projectors - G5, G8, G10, R12 on a regular basis all running at 75Hz with no issues. And I live in a world of PAL.

I have however once had an issue with A Folsom Screen Pro not liking 75Hz.

Cheers

Toby

[samsc]

I know they had problems on eurovision last year.
Cant remember what is was or how they solved it.

I have seen problems with the DL1 running at 75Hz.
It seems to have an internal buffer that works better at 60Hz. if you strobe it at 75hz you get frame glitching. this isnt noticeable with normal footage.

[Sven]

I am using Barco ELM R18s. I have a fairly constant flicker on a few lines at 1280x1024 75Hz. However, while it is noticable on the line-up grid, it is not noticable on the content I have at the momemnt. The content may change to be more graphic with more fine lines and that may show the flicker.
I do not have a lot of head room on the processing side, since I have to run sxga using photo jpeg at 60 sq. Thus I want to avoid running at 60Hz.
I have re-configured the grapics card to overide os settings, but seen no noticable change to the 60hz output.

Sven

[samsc]

I am using Barco ELM R18s. I have a fairly constant flicker on a few lines at 1280x1024 75Hz. However, while it is noticable on the line-up grid, it is not noticable on the content I have at the momemnt. The content may change to be more graphic with more fine lines and that may show the flicker.Sven

could be some kindof active temporal deinterlacing in the barco processing?

They might have a deinterlacing algorithm which works with successive frames?

I havent seen the options available in the barco menus recently.

[samsc]

So I'd just have to find out what playback speed gives 25fps (for correct spped for the footage) when 30Hz playback is selected.

- Fairly simple to establish that level on the playback channel and change the default on the hog profile.

Good workaround - but not really a fix for the DLP's....

You might see a slight visual stutter - just as you get when you slow down any footage-
But there is a lot of this stuttering on TV - with not so good conversions between PAL and NTSC on older TV shows.

Most audiences wont notice.

[tharding]

Is this problem only an issue with the larger panels i.e. 1280 x 1024 in the R series projectors or has it been reported in the G series also?

My experience has predominantly with G series projectors and I have only done a couple of brief demos with some new R12s.

But as I have a month of multiple shows with R12s ahead you have me worried!

Cheers

Toby

[samsc]

sven.

There is a small control panel which claims to be able to switch monitors to 50HZ.

SwitchRes X
http://www.madrau.com/html/SRX/About.html

I installed the demo once, and it did some really wierd things, and i couldnt find a way to uninstall it - so dont do this on a real system.

I also might have to make some slight software changes to run at 50Hz.

[samsc]

There also seems to be something called

DisplayConfigX which does the same thing.

I really havent tried or installed this....

http://voodoofx.all.de/displayconfigx/

this looks quite geeky and scary - but seems to give a lot of control....

[Sven]

Ok. Thanks. I will play around with it when I get a moment.
Very useful to find out all those things which have been disovered in this thread.

Sven

[samsc]

Ok. Thanks. I will play around with it when I get a moment.
Very useful to find out all those things which have been disovered in this thread.

Sven

dont play on a live machine, it might break something....

[samsc]

sven.

if you can make your monitor work at 50hz, i can make a change to the software to help support this.

[samsc]

update to display config:

http://www.macupdate.com/info.php/id/13375

[RichieS]

maybe not an option, but a decent scan-convertor should fix this...

saw a similar problem with the guys on riverdance - running single output 1024x768 75Hz w/Extron scan-convertor to two Barco R18s.

they use black/white strobe for one of the cues. The effect is exactly as Richard describes previously with the DL1s - A very clear banding three-quarters of the way down the image.

I tried every acheivable combination of resolution/refresh-rate. Even tried making the black a very dark blue in case the projector was seeing these frames as a lack of signal???

only way to make it go was to use a Folsom ImagePRO scan-convertor which will happily sit at 200Hz. (As far as I remember, the banding dissapeared at 100Hz)

not sure of your setup there - sounds like you're going 1280x1024 direct into the projectors?

If you're using a scan-convertor, I'd try tweaking there before you make any changes on the G5 - I think your input frequency to the R18s wants to go up instead of down!

Could even be projector problems? If there's a grounding or phasing issue between the signal source and the R18s, it's possible you'll see exactly the same flicker on every projector.

I'm sure you've tried this already, but if it's isolated to individual projectors be sure to try cross-plugging all your inputs in case its something like a convergence problem on the projector, or all your sources to eliminate any scan-convertor issues

Anyway, hope you get to the bottom of it.

Have you had any more problems with the G5s?


Rich Stembridge

[Martin]

I had some issues with performance on a system that was solved switching to refresh rate. The projector boys told me their input had to be 60Hz. Changed it to 75H and using 1024 x 768. This was on a Barco R18.
Worked great.

A buddy of mine works for Barco, i'll let him chime in to tell us how they look at this.


M

[samsc]

saw a similar problem with the guys on riverdance - running single output 1024x768 75Hz w/Extron scan-convertor to two Barco R18s.

they use black/white strobe for one of the cues. The effect is exactly as Richard describes previously with the DL1s - A very clear banding three-quarters of the way down the image.
Rich Stembridge

This means they have their own internal refresh rate - nothing at all can be done about this.
its the way the projector works.

[samsc]

I had some issues with performance on a system that was solved switching to refresh rate. The projector boys told me their input had to be 60Hz. Changed it to 75H and using 1024 x 768. This was on a Barco R18.M

Performance issues are something else.

There is a bug in opengl after about osx 10.3.5 which requires the installation of the ATI displays control panel and software.
otherwise 60hz doesnt work well, but 75 works fine.

Did you check this?

[tharding]

I have been using R12s lately always at 75hz and no issues.

Cheers

Toby

[samsc]

I have been using R12s lately always at 75hz and no issues.

Cheers

Toby

try doing a very fast strobe- one frame on one frame off.

This is NOT a problem with normal usage at all.


just doesnt work well with projectors that do internal processing in a certain way.