I'm working on creating a simple metronome on the iPhone. What the app does right now is to run a timer, entering the timer's function every 1/1000th of second. Then it checks the current time vs time of starting the app (I'm using CACurrentMediaTime() function).
CFTimeInterval currentTime = CACurrentMediaTime();
if (self.beatingStartTime == 0) {
self.beatingStartTime = currentTime;
}
if ( (currentTime - self.beatingStartTime) >= self.timeIntevalBetweenTicks * self.internalTimerCounter ) {
self.internalTimerCounter ++;
// ...
}
If there is a good moment to play audio, the code using OpenAL to play it gets fired.
Basicly that's it. I checked the sounds played when running both in simulator as well as on 2 devices (iPad and jailbroken iPhone 3GS) and there is a problem - when I recorded the sound and reviewed the waveform in Reaper software, some sounds play a bit too late, and some of them - bit too early (even I could understand the "too late" part, I don't really get how it can play earlier then it should - since the app checks the number of seconds every time, it basicly can't be ealier then specified time - yet it is, according to my recods).
At the same time there are some metronome apps that are known for being "rock-solid" when it comes to timing, so I guess there is a way. I just wonder what I'm missing...
edit: Changing timer call from 1/1000th second to, for example 1/100th doesn't help.
edit 2: When I switched from timer to threads (and I put the thread to sleep for specified time) I still get a strange behavior. The tempo moves around and while I could understand a little lag and playing some sounds too late, the problem is some of them do play too early - it means time distance between 2 beats is less then the time that should pass.
The diffrence is about 3%, which translates to about 10-15 miliseconds, which is quite a lot for me. Anyone got an idea why the sound can play earlier? I tried it both on iPhone simulator and on iPad actual device, and my only guess is there's something wrong with the timer - CACurrentMediaTime() returning more seconds that it should. Is it even possible?
Try using an NSSound, and load it up as an instance variable and don't release it unless your metronome isn't running. Delays can be caused by loading the file into memory on the loop. The other thing to consider is that a metronome probably doesn't need to poll every 1/1000th of a second. If you do it less often, you're less likely to saturate the CPU and you might get more consistent results.
Lastly, check out how Apple's demo works: http://developer.apple.com/library/ios/#samplecode/Metronome/Introduction/Intro.html
Might give you a better idea how to accomplish what you're trying to do :)
What you want is COCOS DENSHION which is a simple reliable easy to use sound library, that we have found solves all problems.
I (just personally) don't like "Cocos2D" but you can just take and use CocosDenshion.
Secondly -- 1000th of a second is ridiculous for a timer. Just totally forget it.
Thirdly -- AVAudioPlayer is worthless as you found.
Note - "ObjectAL" is a new, perhaps better, alternative
to CocosDenshion. Check it out.
Related
My app provides voice to AVPlayer and gives a little term using Timer in the middle of playback so that users can read along.
It works well on simulators and real devices.
However, when you pair the air pot, the timer starts about 0.2 seconds late.
Why does this happen and how can I fix it?
I used 'Timer.scheduler' and 'Dispatchqueue.Main.asyncAfter', but both had the same symptoms.
I gather that you are starting playback and simultaneously starting a timer, but when you do this with Bluetooth earphones, that they don’t seem in sync. If that’s the case, I might suggest not using your own timer, but rather let the AVPlayer tell you where it is.
For example, you might use addPeriodicTimeObserver(forInterval:queue:using:). The AVPlayer tell you when it got to a particular point in the playback.
I've done a simple audio playback GUI implemented using AVAudioPlayer.
When playing my sound, I use a UISlider to provide playback feedback...
Here's where it gets weird.
I have a problem that happens very (very) sporadically - and mostly it doesn't happen, making it really hard to debug.
The problem is that sometime, once the sound ends, and I play it again, it's as if it starts looping (as if I set numberOfLoops to -1), without ever calling audioPlayerDidFinishPlaying.
Now, no where is my code do I "touch" numberOfLoops - it defaults to 0, and I leave it that way.
To make the problem weirder, then once this problem happens, I don't "hear" the audio - though it does appear to play (i have a timer function that provides the visual feedback, and it checks the sound is playing...)
Any ideas? Directions?
I faced the same issue once and I got around the issue by increasing the updating timer interval to .25 seconds,which was earlier .1 seconds. Also I tried to avoid files with very small duration. Hope this helps you to some extend. Please try it and let me know if it worked for you.
I need to play sounds (~5 seconds each) throughout my iphone application. When they're triggered, they need to play immediately.
For the moment I'm using AudioServices and (as you probably know) the first time you play a sound it lags, then every time there after it's perfect. Is there some code available that's clever enough to preload an AudioServices sound (by playing it silently maybe?). I've read adjusting the system volume programmatically will get your app rejected, so that's not an option. Seems AudioServices isn't made for volume correction from what I can see.
I've looked into OpenAL and while feasible seems a little over kill. AVAudioPlayer seems like a little bit of a better option, I'm using that for background music at present. Extending my music player to handle a 'sound board' might be my last resort.
On the topic of OpenAL, does anyone know of a place with a decent (app store friendly) OpenAL wrapper for the iPhone?
Thanks in advance
Finch could be perfect for you. It’s a tiny wrapper around OpenAL with very low latency and simple API. See also all SO questions tagged ‘Finch’.
If you use an AVAudioPlayer, you can call prepareToPlay when you initialize the object to reduce the delay between calling play and having the audio start.
Finch uses OpenAL. However, when I have an instance of Sound, and say -play, the sound plays. When I call -play multiple times one after another in a fast paced way, every -play makes the current sound playback of that sound stop and restart it.
That's not what I want. Would I have to create multiple sources or buffers to get that working? Or would I just instantiate multiple Sounds with the same file?
There’s a RevolverSound class exactly for this use case. It’s very simple, it allocates a number of Sound instances beforehand and then plays them in rotation:
- (void) play
{
[[sounds objectAtIndex:current] play];
current = (current + 1) % [sounds count];
}
This means that there is a hard limit of the sounds that can play simultaneously and the memory usage goes up with that limit. I didn’t find that to be a big problem in practice, because when there are five or more sounds playing at once, there’s already such a sonic chaos that you generally won’t notice that the first one did not play to the very end before starting again.
I have used:
[UIApplication sharedApplication].idleTimerDisabled = YES;
in a number of Apps developed and running under iPhone OS 2.x and never had any problems with it. They were clock apps so needed to run constantly and ignore the iPhone's idle Timer setting.
However, trying to achieve the same with a new App running OS 3.0 (and which needs to be deployed under 3.0 as it uses some 3.0 APIs) I've found the idle Timer to be either ignored or inconsistent.
My App plays music from the iPod library and when the music is playing it auto-locks regardless of the above setting. But once you unlock it, it then doesn't auto-lock again unless you play music again, in which case it locks again after the iPhone auto-lock time setting.
I'm amazed no-one else has come across this as I imagine it would affect a large number of Apps.
Just to clarify:
1. The above code is in ApplicationDidFinishLaunching
2. I know that the phone won't auto-lock when testing from xCode regardless of settings
If anyone has any thoughts I'd be very grateful...
Our app uses the MPMediaPLayer. We also had the idleTimerDisabled=YES code in the ApplicationFinishedLaunching, which works EXCEPT if untethered, and there is already a current nowPlayingItem which is left playing (or unpaused, if paused at app startup). Obviously this is all with the Settings -> General -> Autolock set to some timed value.
By adding idleTimerDisabled=NO, immedately followed by idleTimerDisabled=YES in one of the other bits of code AFTER we had figured out what bit of music we would get playing seemed to solve the problem. Just setting it to YES was insufficient.. and subsequent queries had always indicated the correct value (YES).. so it appears the Apple code ignores the setting of the value IF there is a current piece of music and that is not changed by your code.. but does notice a change of value.
This is all under iOS 3.0.
Even in 2015, using iOS 8.2, this bug is still alive and kicking.
Here's my solution, using XCode 6.2.
iPhone - phone goes to sleep even if idleTimerDisabled is YES
Basically, even now, in 2015, the only way to safely make sure that the device doesn't go to sleep is to repeatedly call a piece of code to keep the device awake.
-(void)callEveryTwentySeconds
{
// DON'T let the device go to sleep during our sync
[[UIApplication sharedApplication] setIdleTimerDisabled:NO];
[[UIApplication sharedApplication] setIdleTimerDisabled:YES];
}
Sounds like a bug, file with Radar - I am not too surprised this has not been seen much as there are probably not a lot of apps that try to lock the screen open and play music.
Having same issue. It does work when the device is plugged in. You can press lock button on top, and my NSTimer fires later and causes a vibrate. However if the device is not plugged in pressing the lock button puts the device to sleep. Any solution would be greatly appreciated.
iCodeblog posted about the idletimer, I said it didn't work, and the person who develops 'cute clock' was nice enough to reply. You have to do a hack, play a 1 second or longer silent sound every 10 or so seconds with NSTimer. This keeps the device awake even if the user hits the lock button.
I develop Seconds - Interval Timer for iPhone and iPod touch and I've had no end of trouble with this. The idea of my app is that people create timers based on a number of intervals where each interval can have it's own playlist or track played.
In iOS3 I had the problem that I couldn't disable the idle timer by just setting idleTimerDisabled = YES. In the end I came up with the same solution as Neil whereby I would periodically set it to NO, then immediately to YES again. This seemed to work.
I'm now updating the app to iOS4 (I know, iOS5 is just around the corner...) and now I have the opposite problem. If the MPMediaPlayer changes track before the idle timer reaches it's limit it gets reset. I've just tested this by creating an interval in my app that was 55 seconds, my auto-lock was set to a minute. At 50 seconds the screen dimmed as it prepared to lock, but at 55 seconds when the music changed it went back to full brightness and then didn't lock as it should.
Overall, the implementation of this seems flakey at best.