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How to control the framerate in KineticJS?

How can I control the rendering loop frame rate in KineticJS? The docs for Kinetic.Animation show a frame rate being passed to the render callback, and Kinetic.Tween seems to have no frame rate logic, but I don't see anyway to force, say, a 30fps when 60fps is possible.
Loads of context for the curious follows, but the question is that simple. If anyone reads on, other advice is welcome. If you already know the answer, don't waste your time reading on!
I'm developing a music app that combines some DOM-based GUI controls (current iteration using jQuery Mobile) and Canvas-based GUI controls (using KineticJS). The latter involve some animation. Because the animated elements are triggered by music playback, I'm using Kinetic.Tween to avoid the complexity of remembering how long a given note has been playing (which Kinetic.Animation would require doing).
This approach works great at 60fps in Chrome (on a fast machine) but is just slow enough on iOS 6.1 Safari (iPad 2) that manipulating controls while animations are happening gets a little janky. I'm not using WebGL (unless KineticJS or Chrome does this by default for canvas?), and that's not an option when I package for native UIWebView.
As I'm getting beyond prototype into wanting to make more committed tech decisions, I see the following options, in order of perceived goodness:
Figure out how to cap the frame rate. Because my animations heavily use alpha fades but do not involve motion, I believe I could get away with 20-30fps and look fine. Could also scale this up on faster devices.
Don't respond immediately to touch inputs, but add them to a queue which I poll at a constant interval and only use the freshest for things like touchmove. This has no impact on my non-interactive animated elements, but tackles the problem from the other direction, trying to reduce the load of user interaction. This would require making Kinetic controls static and manually tracking touch coordinates (not terrible effort if it actually helped).
Rewrite DOM-based GUI to canvas-based (KineticJS); rewrite WebAudio-based engine to HTML5 audio; leverage CocoonJS or Ejecta for GPU-acceleration. This means having to hand-code stuff like file choosers and nav menus and such (bad). Losing WebAudio is pretty serious as it eliminates features like DSP effects and very fine-grained, low-latency timing (which is working just fine on an iPad 2).
Rewrite the app to separate DOM based GUI and WebAudio from Canvas-based elements, leverage CocoonJS. I'm not sure if/how well this works out, but the fact that CocoonJS passes JavaScript code as strings between the 2 components makes me very skittish about how solid this idea is. It's probably doable, but best case I'm very tied to CocoonJS moving forwards. I don't like architecting this way, but maybe it's not as bad as it sounds?
Make animations less juicy. This is least good not because of its design impact but because, as it is, I'm only animating ~20 simple shapes at any time in my central view component, however they include transparency and span an area ~1000x300. Other components like sliders are similarly bare-bones. In other words, it's not very juicy right now.
Overcome severe allergy to Objective-C; forget about the browser, Android, and that other mobile OS. Have a fast app that performs natively and has shiny Apple-approved widgets. My biggest problem with this approach is not wanting to be stuck in Objective-C reality for years, skillset-wise. I just don't like it.
Buy an iPad 3 or later. Since I already am pretending Android doesn't exist (I don't have any devices to test), why not pretend no one still has iPad 2? I think this is passing the buck -- if I can get acceptable performance on iPad 2, I will feel confident about the app's performance as I add more features.
I may be overlooking options or otherwise naive about how to tackle this. Some would say what I'm trying to build is just silly. But it's working pretty well just not ready for prime time on the iPad 2.

Yes, you can control the Kinetic.Animation framerate
The Kinetic.Animation sends in a frame object which has a frame.time property.
That .time is a running timer that you can use to throttle your animation speed.
Here's an example that throttles the Kinetic.Animation: http://jsfiddle.net/m1erickson/Hn3cC/
var lastTime;
var frameDelay=1000;
var loop = new Kinetic.Animation(function(frame) {
var time = frame.time
if(!lastTime){lastTime=time;}
var elapsed = time-lastTime;
if(elapsed>=frameDelay){
// frameDelay has expired, so animate stuff now
// set lastTime for the next loop
lastTime=time;
}
}, layer);
loop.start();

Working from #markE's suggestions, I tried a few things and found a solution. It's ultimately not rocket science, but sharing what I figured out:
First, tried the hack of doubling Tween durations and targets, using a timer to stop them at 50%. This kinda sorta worked but was hard to get to look good and was pretty error prone in coding bogus targets like negative opacity or height or whatnot.
Second, having read the source to Tween and looked at docs again for Animation, decided I could locally use Animation instances instead of Tween instances, and allow the closure scope to hang onto the relevant note properties. Eventually got this working smoothly and finally realized a big Duh! which is that throttling the frame rate of several independently animating things does not in any way throttle the overall frame rate.
Lastly, decided to give my component a render() method that calls itself in a loop with requestAnimationFrame, exits immediately if called before my clamp time, and inside render() I update all objects in the Kinetic canvas and call layer.drawScene(). Because there is now only one animation, this drops frame rate to whatever I need and the app is fast on iPad 2 (looks exactly the same to my eyes too).
So Kinetic is still helping for its higher level canvas API, and so far my other control widgets are still easy code using Kinetic to handle user input and dragging, now performing much better as the big beast component is not eating up the CPU.
The short answer to my original question is that no, you can't lock the overall frame rate for very complex animations, but as Mark said, you can for anything that fits in a single Animation instance.
Note that I could have still used Animation without giving it a layer or explicitly calling any draw() methods, but since I'd still have to write all the logic to determine individual element's current visual state, there was no gain to doing this. What would be very useful would be if Tween could accept a parameter to not automatically render. This would simplify code like mine, as I could shorthand the animation on individual objects but still choose when to actually do the heavy lifting of rendering everything. Seeing how much this whole exercise gained in performance on the iPad 2, might be worth adding this option to the framework.

Are css animations still faster than javascript animations in ios 6+?

To animate an element, we can use css animations, or we can do it in javascript.
Reading up on this, it seems like css animations are expected to render more quickly than javascript animations, since the browser can execute css animations in native code. This info was gathered from posts dated from 2008 - 2011.
With ios 6, is this still the case? In the release notes, I found this item:
"WebKit no longer always creates hardware-accelerated layers
for elements with the -webkit-transform: preserve-3d option.
Authors should stop using this option as a way to get hardware
acceleration."
http://developer.apple.com/library/ios/#releasenotes/General/RN-iOSSDK-6_0/_index.html
Since I'm pretty new to animations in the web, I'm not sure what the current status is,
Thanks

CSS animations and transitions will always be faster than JavaScript ones, simply because there is just a single instruction to be handled, as opposed to having to follow all the JS instructions required for the same effect.

I'd interpret the release message as "It is no longer guaranteed that a value of preserve-3d enforces hardware acceleration" (and should not be used as a hack to assert HA). If the UA chooses not to use HA, it will have good reasons for that.
Regardless, native implemented CSS transitions are still faster than manual JS animations (in general, at least). Also, there is no cause for using JavaScript when you can achieve the same thing with short [basic] CSS.

Why is my requestAnimFrame still slow?

I have followed the best practices to draw a simple animation using requestAnimFrame :
http://jsfiddle.net/paul/XQpzU/2/light/
Unfortunately the animation has lags even on this example (on Chrome, Firefox and IE).
The explanation of the source code is there : http://paulirish.com/2011/requestanimationframe-for-smart-animating/
What is the solution do display a simple animation in html5 without any slow down?

Use double buffer technique for complex animations to avoid slow functions like save, restore and so on.
Good article
http://www.felinesoft.com/blog/index.php/2010/09/accelerated-game-programming-with-html5-and-canvas/
"requestAnimFrame" will not give you performance boost, because in this case browser decides whether to render your code in the certain time, not you. My experience shows that its better to set timer for the required FPS. I had bad experience when wrote the game using PhoneGap for Android. I tried various techniques and the best was to use two canvases, to reuse paths and avoid slow transformation functions.

Javascript Game: What should i know?

I am thinking as a challenge i should write a javascript based game. I want sound, images and input. A background to simulate a screen (like 640x480 with all my images in it) would be useful to separate the rest of the page from the 'game'. What should i look at?
Some things i would need
Framecontrol. A way to get the current time (or delta).
Image, displaying it and moving it. How do i display full image. Knowing pixel access may be cool.
Input A way to lock it in a box (like flash does) is cool.
Sound play simple sounds on demand (like when i get a hit). Several sounds at once would be great
Bottlenecks. What are things that will kill the CPU?
Restrictions. What cant i do? I hear i cant 'sleep' to wait. I must set a callback
Good or best pratice. What are good things i can do to either keep speed up or to lower glitch or compatibility problems.

I'm going to answer this looking at things from a mootools javascript perspective:
Framecontrol. A way to get the current time (or delta).
periodical()
Image, displaying it and moving it. How do i display full image.
setStyles()
Input A way to lock it in a box (like
flash does) is cool.
Plain old CSS
Sound play simple sounds on demand
(like when i get a hit).
Swiff, remote();
Bottlenecks. What are things that will
kill the CPU?
Internet Explorer.
Restrictions.
3D ... ?
What are good things i can do ... to
lower glitch or compatibility
problems.
Use a framework.

As a starting point, you may want to write it for Opera, as Opera provides a game canvas that will help you out.
For some examples of games in javascript:
http://dev.opera.com/articles/view/3d-games-with-canvas-and-raycasting-part/
http://my.opera.com/WebApplications/blog/show.dml/200788
This one is interesting, it is demos of games using the canvas element.
http://www.canvasdemos.com/tag/games/
The best way to see where the problems are is to start writing the game, and then you will see what may be a problem. By looking at demos you can get an idea what performance issues they encountered. For example, a full 3D Doom game will have problems, but, as the first article above explains, there are some ways to optimize for javascript.
Once you get it working with Opera, then you can look at Firefox 3.5+ and Safari, as well as Chrome, and see if you can make some changes to have it work on those. How many platforms it works on depends on how much work you want to do for it. For a proof-of-concept pick the easiest browser for your task.

The best place to start would be to get very familiar with the <canvas> tag (it allows you to draw anything on screen)
This may help a lot:
http://benfirshman.com/projects/jsnes/
its an online NES emulator that renders everything on screen - the source is also available
Hope that helps =)

What's the best way to apply a drop shadow?

What is the best method for applying drop shadows? I'm working on a site right now where we have a good deal of them, however, I've been fighting to find the best method to do it. The site is pretty animation heavy so shadows need to work well with this.
I tried a jQuery shadow pulgin. The shadows looked good and were easy to use but were slow and didn't work well with any animations (required lots of redrawing, very joggy).
I also tried creating my own jQuery extension that wraps my element in a couple gray divs and then offsets them a little bit to give a shadow effect. This worked well. It's quick and responsive to the animation. However, it makes DOM manipulation/traversal cumbersome since everything is wrapped in these shadow divs.
I know there has to be a better way but this isn't exactly my forte. Thoughts?

ShadedBorder is a good looking and easy to use Shadow-Library. check it out

You don't need to wrap those shadow-divs around the other content, just set them a little askew and place them on a lower z-index !-)

if your main problem is to navigate the DOM, just add a class and/or id to your element, and refer it with JQuery selectors. even better if you store the ref in a variable, so you don't need to select it too frequently

Although it is yet to have full cross-browser support, you might like to try using the CSS 3 text-shadow property.

It largely depends on how frequently your images will need to be changing, and the colored areas that they'll be covering. Because I'm guessing that you'll be needing to pay attention to IE6 compliance, most alpha-PNG solutions will cause such horrible jittery-ness that you'll spend more time in performance optimzation than you would have wanted to guess.
To solve this in the past, since our images are modified less than once a month, we call the images through a caching-PHP script which automatically applies the shadow using a pre-defined background color so we don't have to rely on any transparency. This results in faster downloads (fewer HTTP requests) and a faster-interface because there's less Javascript/CSS magic in the works.
I understand that this is a very old-school solution, and the above solutions would be entirely acceptable if your images were static, but being cross-browser compliant and animated will likely force you to do a solution of this style.