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    <p>As Steve points out, in my answer <a href="https://stackoverflow.com/questions/5156872/how-to-apply-filters-to-avcapturevideopreviewlayer/5158856#5158856">here</a> I encourage people to look at OpenGL ES for the best performance when processing and rendering images to the screen from the iPhone's camera. The reason for this is that using Quartz to continually update a UIImage onto the screen is a fairly slow way to send raw pixel data to the display.</p> <p>If possible, I encourage you to look to OpenGL ES to do your actual processing, because of how well-tuned GPUs are for this kind of work. If you need to maintain OpenGL ES 1.1 compatibility, your processing options are much more limited than with 2.0's programmable shaders, but you can still do some basic image adjustment.</p> <p>Even if you're doing all of your image processing using the raw data on the CPU, you'll still be much better off by using an OpenGL ES texture for the image data, updating that with each frame. You'll see a jump in performance just by switching to that rendering route.</p> <p>(Update: 2/18/2012) As I describe in my update to the above-linked answer, I've made this process much easier with my new open source <a href="https://github.com/BradLarson/GPUImage" rel="nofollow noreferrer">GPUImage</a> framework. This handles all of the OpenGL ES interaction for you, so you can just focus on applying the filters and other effects that you'd like to on your incoming video. It's anywhere from 5-70X faster than doing this processing using CPU-bound routines and manual display updates.</p>
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    1. POHow can I do fast image processing from the iPhone camera?
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    1. POHow can I do fast image processing from the iPhone camera?
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    1. COi am ALSO asking if the way i am doing it - getting UIImage from SampleBuffer through CGImage (like the examples in avfoundation) and then calling performSelectorOnMainThread with setNeedsDisplay (then drawImageAtPoint) is CORRECT (?) - drawing takes about 30 ms and performSelector also 30 ms so i get <20 fps for no processing and minimal camera resolution - maybe i do something wrong - especially i am not sure about this performSelector code
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    2. CO@user641443 - Your process of updating your image view is correct, because you need to run updates like this for standard UI elements on the main thread (thus the `-performSelectorOnMainThread:`). What's taking the time is the Quartz drawing to the screen of your image. As I suggest, you can significantly speed up this display process by using OpenGL ES to render your image as a texture. You won't even need to call back to the main thread to update such a texture, leading to a more responsive interface. I highly recommend looking at this for your kind of video display.
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    3. COmuch tnx for answers - but listen to this: my measurings show that drawing (scalling included) takes about 30 ms - not so fast but maybe ok - and waiting on perform selector on main thread also takes about next 30 ms - is that correct value for such 'perform selecor'? a would optymise drawing but it is only half a time
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