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Editorial Team
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Asked: 2026-06-13T22:26:07+00:00

I have created an iOS 5/iOS 6 app with a display that responds to

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I have created an iOS 5/iOS 6 app with a display that responds to changes in the musical pitch performed by the user. It uses the record function in the sample SpeakHere code but does not actually save a file because it is designed to respond in real time.

I would now like to extend this app to respond simultaneously to the pitch itself and the duration that the same pitch is sustained (for example, changing the color when the same pitch is held steadily for a minimum period of time). I have been reading about NSTimer and NSDate functions, which seem straightforward, as well as AudioTimeStamp functions, which are apparently C based and which I find very confusing. Based on other posts, it seems like NSTimer and NSDate checks might cause the display’s real-time response to an actual musical performance to lag. How about dispatchAfter? Could I expect the block to execute at the scheduled time?

My question is, what approach is most likely to yield the desired result of allowing me to measure duration of a particular pitch in the AudioQueue and update my display continuously in real time? Do I need to be saving to a file for this to work?

I am self-taught and have only been programming for a few months, so no matter what I will have to do a lot of learning of APIs/C language features that are new to me. I’m hoping someone can point me in a fruitful direction. Thanks!

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1 Answer

  1. Editorial Team

    You’re definitely getting into pretty advanced stuff here. Here are a few thoughts:

    1. Your audio processing seems to be the most intensive operation. Because this processing needs to be continuous, you’re probably going to have to do this processing in another thread. By processing, I mean examining the audio to determine pitch.

    2. Once you’ve identified the pitch, you should store the time for which it began.

    3. Then, in the main thread, setup an NSTimer that repeats continuously and in the NSTimer’s fire method, subtract the pitch’s start date from the current date to get the elapsed time, as an NSTimeInterval.

    4. Send the NSTimeInterval to your display logic so that you can update the color on screen.

    Some things to check out:

    Beginner’s tutorial on multi-threading and Grand Central Dispatch on iOS
    NSTimer

    Using NSTimers

    Hope that helps you out!

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