I have a custom UISlider and use the currentPlaybackTime to change values of an MPMoviePlayerController object.
The problem is when i scrub at a fast rate using the slider, it doesn't respond as fast as i would like..
Is there any better way to have a fast interactive scrubber for ipad? targeting from OS 3.2
Well there are two issues, only one you can control directly.
Multimedia-content is commonly compressed using some kind of delta-compression, hence quick and exact seeking is not a trivial task to cope with. As that is common and since you can not directly change that, you will have to live with it.
the only way to increase responsiveness for seeking on the content-side (when encoding) is reducing the gop-size - that is, less p-frames between the i-frames.
when using a slider or a similar control, you could, instead of directly connecting the current playback position with it, handle any manual changes in an indirect fashion. You could run a timer based job that, whenever the slider/scrubber has been moved, tries to adjust the playback position towards that new value. Once the player is seeking, prevent the scrubber from getting feedback from the current playback location but allow it once the player is in playing state again. That way the user does not directly experience the clunky seek feedback.
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I am developing an aframe project on my MacBook pro, late 2013. When running the project, the fan of my computer always spins fast, regardless which browser I use (firefox, safari, chrome) and the project size (also happens with a project just containing a simple a-box).
aframe-stats show me that my project (1028244 vertices, 342748 faces) still runs with 20 fps.
Is it somehow possible to limit the frame rate to 10fps in order to keep my computer quite? Or any other way to limit the flop-consumption of the aframe project? I already tried a native approach with sudo cputhrottle plugin-container 10 but that did not just throttle the aframe-renderer but the whole firefox browser. Can I pull the break somewhere in the JavaScript or the Browser settings?
It's difficult to say without your project code. Large data sets will simply crank out even a high spec macbook pro. I have found it helpful to pause any rendering whenever possible to quiet the users' machines.
I personally removed automated next animation frame rendering in favor of waiting for controls and objects to change.
For example:
this.controls.addEventListener( 'change', function(e){ addToRenderStack(); });
A simple function addtorenderstack puts in a new value in a list for a render, with the expectation that the render will occur at some point in the future and not right away. the list can also be used to log who requested the render in the call stack, and narrow down performance hogs.
addtorenderstack places a render request in a list. In the requestanimationframe loop, if the list has any length, a render is called on the scene. The stack is immediately cleared rather than processed one by one. If controls or animations continue to make render requests, the list will have a length again and request animationframe will process them in the same way with another render.
In this way, the code only renders when absolutely required. This saved me much grinding on framerate and the fans only come on during intensive operations and then shutdown when its complete, much like a typical 3d game experience.
Your mileage may vary depending on what's happening in your app. I work in engineering so often the view of the 3d world is stopped as an engineer examines or shows a model.
I am making a drawing on NSView using a timer that is set to update every .02 seconds. On update some physical simulation makes a step, and then Canvas!.needsDisplay = true. It works when app is in foreground (usually), but when some lags happen, simulation progresses forward despite the fact that view hasn't reflected it yet. How do I pause the timer during these times to make simulation happen only when NSView can show it? I do not want to call step_over from inside drawRect, cause it seems like a bad idea, because then it would be harder to stop the simulation.
Generally this kind of update should be done the other way around, by letting the display ask you for frames as it can display them. This is done with a CADisplayLink CVDisplayLink (this is Mac; CADisplayLink is iOS). Configure it with a method you want to be called when a frame can be drawn.
Generally you do want your simulation to keep moving forward, even if it means dropping frames occasionally. For that, you check the timestamp and use that to work out what time to use for your new frame. But if you only want to move forward when the display can show it, then just update once per call.
Note that generating at 50fps is often going to mismatch the system that's trying to draw at 60fps, so you're going to wind up missing frames occasionally. That's one of several reasons not to try to push drawing with a timer.
See also Alternative of CADisplayLink for Mac OS X. Note that trying to draw at 50fps with Core Graphics usually isn't going to give good results in any case. The right tool here in OS X is Core Animation (or SpriteKit for games on 10.10, or OpenGL for more advanced high-speed rendering). You can do very basic animations with an NSTimer (and we did for years before Core Animation came along), but it's not really a tool for complex drawing.
I would like to make a a software setup that would let the user switch between two webcam feeds (or more but let's consider two). I would like a fade in/out effect while switching. My main problem is that I don't know how to start.
There seems to be some ffmpeg tool that could do the job (like libavfilter) but I don't get how I could setup it.
What should I consider to use if I want to access frame image to make the transition myself? Is there some simpler way?
I know that this question looks really poorly written, but I'm as lost as I look.
I have a scenario that I need some good solid advice on. The question is really about speed of WriteableBitmap vs. images in IsolatedStorage on the Windows Phone.
I have an app that displays a UserControl (#1) which is a little graphically heavy. When the user swipes it, it transitions in a push-left type of transition to bring in a new UserControl (#2) which is also a little graphically heavy. If the user swipes the other way, control #1 is brought in in the same type of push-transition, this time from the right.
What I do today is take a snapshot of #1, load #2 off screen and take a snapshot of it, put both side-by-side in a Canvas control and animate that control either left or right. One of the reasons I don't just use the controls and animate them is they may have animation that starts when they are loaded - my current technique allows me to capture a screen shot of pre-animation and post-animation, depending on which direction they go in.
What I'm wondering, however, if it would be better/faster to just do the above the first time and send the writeablebitmap to IsolatedStorage with Extenstions.SaveJPEG and just use that instead in subsequent tranistion animations.
Would load/render/WriteableBitmap each time generally be faster or load jpeg from IsolatedStorage be faster each time? I see that the Transitions control in the SDK doesn't really do either of these, so I'm open to suggestions that are different that also might improve performance.
I expect this to be very depended on the hardware and application. So it is pretty hard to give an answer based on this input. It doesn't look to hard to test (on actual hardware and with the actual application) so my advice is to build both and test.
The applications I have been working with use both approaches and to be honest I haven't noticed much difference.
Also you might try and enable bitmap caching on the controls. This will give you a writeable bitmap implementation that is very fast.
I'm writing a video annotation application with Qt4 in which users need to be able to seek to various points in a video, putting markers on various objects and then setting keypoints for those markers so that they stay on the objects in the video as they move around. QGraphicsItemAnimation seems like a great place to start for these markers, however they need to be able to appear and disappear at specific times, which I can't figure out how to do with the QGraphicsItemAnimation. I could set the scale at 0 to make the objects disappear, but that seems like a pretty hacky solution, and I'm guessing that the paint engine would still waste cpu cycles trying to draw those invisible objects. Does anyone have a better solution than this? I'm using Qt 4.5.3 right now, but I'm willing to upgrade to 4.6 if it makes things easier. Thanks!!
It seems like the functionality you want of showing/hiding QGraphicsItem objects is beyond the scope of the simple "tweening" that the animation class performs. It is only for one object at a time, and any appearance or disappearance you have to write yourself.
You still might get some mileage out of QGraphicsItemAnimation (although the fact that it uses its own timer instead of being locked to the frame clock of your video is a little dodgy).
Neglecting "seeking" for a moment, there is a QTimeLine::finished() signal. If you let the end of an annotation's active animation timeline represent the point where you want it to disappear, you can trigger QGraphicsItem::hide() at that point. When it comes time to turn it back on, you would construct a new QGraphicsItemAnimation (based on the next run of keyframe data for that object) and call QGraphicsItem::show().
Note that one of the headlining features of Qt 4.6 is the QtAnimation framework, which is more sophisticated but also rather complex. I've not used it yet, but looking over the examples it seems like you might be able to "animate" a visibility or opacity property.