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POAVAudioRecorder averagePowerForChannel always returns -120.0
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  1. POAVAudioRecorder averagePowerForChannel always returns -120.0
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    copied!<p>I'm trying to use AVAudioRecorder's averagePowerForChannel method to monitor input levels on the microphone for an iPad/iPhone app. I have a callback which polls the average level in a loop — on the iPhone it works fine and returns sensible levels, but for some reason on the iPad it always returns -120.0. </p> <p>Here's some of my setup code:</p> <pre><code>- (void) setupMic { if (micInput) { [micInput release]; micInput = nil; } NSURL *newURL = [[NSURL alloc] initFileURLWithPath:@"/dev/null"]; NSMutableDictionary *recordSettings = [[NSMutableDictionary alloc] init]; [recordSettings setObject:[NSNumber numberWithInt:kAudioFormatAppleLossless] forKey: AVFormatIDKey]; [recordSettings setObject:[NSNumber numberWithFloat:22050.0] forKey: AVSampleRateKey]; // [recordSettings setObject:[NSNumber numberWithInt:2] forKey:AVNumberOfChannelsKey]; [recordSettings setObject:[NSNumber numberWithInt:12800] forKey:AVEncoderBitRateKey]; [recordSettings setObject:[NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey]; [recordSettings setObject:[NSNumber numberWithInt: AVAudioQualityLow] forKey: AVEncoderAudioQualityKey]; micInput = [[AVAudioRecorder alloc] initWithURL:newURL settings:recordSettings error:nil]; // [micInput setMeteringEnabled:YES]; [newURL release]; [recordSettings removeAllObjects]; [recordSettings release]; } </code></pre> <p>As well as my start recording method:</p> <pre><code>- (void) startRecording { NSLog(@"startRecording!"); [micInput pause]; [micInput prepareToRecord]; micInput.meteringEnabled = YES; [micInput record]; [micInput updateMeters]; levelTimer = [[NSTimer alloc] initWithFireDate:[NSDate dateWithTimeIntervalSinceNow:0.0] interval:0.03 target:self selector:@selector(levelTimerCallback:) userInfo:nil repeats:YES]; [[NSRunLoop currentRunLoop] addTimer:levelTimer forMode:NSDefaultRunLoopMode]; } </code></pre> <p>and a bit of the levelTimer callback:</p> <pre><code>- (void)levelTimerCallback:(NSTimer *)timer { [micInput updateMeters]; double avgPowerForChannel = pow(10, (0.05 * [micInput averagePowerForChannel:0])); [micSprite receiveInput:avgPowerForChannel]; NSLog(@"Avg. Power: %f", [micInput averagePowerForChannel:0]); ... } </code></pre> <p>Where on the iPhone, the NSLog statement will return sensible values, and the iPad will always return -120.0. </p> <p>Note: I'm using this inside of a cocos2d application. For some reason, if I restart the current scene on the iPad, the mic levels will return correct values.</p> <p>Anyone have any suggestions? I'm seriously at a loss here. Thanks!</p>
 

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