Livecode for Digital Signage

Nonsanity form at nonsanity.com
Wed May 18 10:32:40 EDT 2011


I see your problem then. In my sample stack, the text display area is 800
pixels wide. Going by the speed you set it to, that means the text is moving
1 pixel every 4 milliseconds. No WONDER you're getting jerky motion.

With the 300 speed setting change you made, I could make it smooth by
setting the send in time delay to 10-15 milliseconds. But with the script
(simple as it is) executing that often, it is VERY susceptible to upset from
any other task running on that computer. Any delay elsewhere inside the
computer results in a visible stutter as it misses a few updates.

Also at that speed, there's an increased chance of intersecting the screen
refresh rate, which results in a momentary sheering effect along the text.
The sheer and the stutter combine to keep the text from looking solid when
moving that fast.

Tickers as seen on TV are sync-locked to the video stream, I believe, which
makes them far more stable. They are also usually on dedicated hardware and
not a home desktop computer that's running who-knows-what in the background.

I don't think you're going to be able to get that fast a speed without
temporal artifacting in LiveCode. Can you slow it down?

But even at one third that speed, you will still see the occasional sheer
(far less frequently) and some stuttering (other tasks are still running,
after all) though that is less noticeable because less distance is being
skipped at that speed..

the only way I can think of to get a sure-fire smooth scroll at ANY speed
would be to offload the work to a graphics card. Then the updates would be
synced to the display's refresh rate (no sheer) and no other tasks are
running on the graphics card CPU (so no stutter). But you can't do that in
LiveCode currently. (OpenGL support on the roadmap, anyone?)

 ~ Chris Innanen
 ~ Nonsanity



On Wed, May 18, 2011 at 1:17 AM, Jim Schaubeck <jimschaubeck at yahoo.com>wrote:

> Chris,
> Thank you for sending your sample !!!
>
> I worked with your code a bit and changed this line:
> put dTime / 300 into pTime-- changed to 300
>
> This made the test move a similar speed (faster than your speed) to a stock
> ticker tape but I still have the jerkiness.
>
> I will save your project for future reference though, thanks again!
>
> jim schaubeck
> 714-321-4499
>
>
> -----Original Message-----
> From: use-livecode-bounces at lists.runrev.com
> [mailto:use-livecode-bounces at lists.runrev.com] On Behalf Of Nonsanity
> Sent: Tuesday, May 17, 2011 10:05 PM
> To: How to use LiveCode
> Subject: Re: Livecode for Digital Signage
>
> Using hscroll of a field and the send in time command, I got very smooth
> text scroll on my Macbook Pro. Here's the stack I tested with:
>
>
> https://dl.dropbox.com/s/l4gc4mp0401j6se/Smooth%20Scrolling%20Text.livecode?
> dl=1<https://dl.dropbox.com/s/l4gc4mp0401j6se/Smooth%20Scrolling%20Text.livecode?%0Adl=1>
>
> Let me know how it works for you.
>
>  ~ Chris Innanen
>  ~ Nonsanity
>
>
>
> On Tue, May 17, 2011 at 10:28 PM, Jim Schaubeck
> <jimschaubeck at yahoo.com>wrote:
>
> > I would like to develop an in-house digital signage app that uses
> > video, animation and smooth scrolling words (like a stock ticker).  I
> > can figure out the video and the animation but I'm having trouble with
> > smooth scrolling text.  Is this better suited for Animation Engine
> > (have not tried it) or is there a trick to getting text to flow
> > Right-to-Left smoothly.  The best that I can see is the move command
> > but it's still too jerky for displaying in a store.
> >
> >
> >
> > Thank you for any feedback
> >
> >
> >
> > jim schaubeck
> >
> > 714-321-4499
> >
> >
> >
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