Trying to understand AVAudioPlayer and audio level metering

avaudioplayer, ipad, iphone, objective-c, xcode

Solution

You're updating and then asking for the value of the meters almost immediately after the sound starts -- that `updateMeters` is probably running a few tens of milliseconds after you send `play`. So if there's any silence at the beginning of the clip, you could very well be getting the correct reading. You should trying delaying your inspection, and you may also need to send `updateMeters` inside the loop, right before you inspect the values.

You're also never actually getting the meter values for channels > 0, because you pass 0 no matter what the value of `i` is in the loop. I think you meant to do this:

for (int currChan = 0; currChan < channels; currChan++) {
    //Log the peak and average power
    NSLog(@"%d %0.2f %0.2f", currChan, [audioPlayer peakPowerForChannel:currChan], [audioPlayer averagePowerForChannel:currChan]);
}

Problem

I'm trying to understand AVAudioPlayer and audio level metering. What I have below is an object "AudioPlayer" that is playing a short audio sound. Now I want to output the power of this sound (decibels). Somehow I don't think I'm doing this right. ``` audioPlayer.meteringEnabled = YES; [audioPlayer play]; int channels = audioPlayer.numberOfChannels; [audioPlayer updateMeters]; for (int i=0; i<channels; i++) { //Log the peak and average power NSLog(@"%d %0.2f %0.2f", i, [audioPlayer peakPowerForChannel:0],[audioPlayer averagePowerForChannel:0]); ``` The NSLog output of this is 0 -160.00 -160.00 1 -160.00 -160.00 Now according to Apple "A return value of 0 dB indicates full scale, or maximum power; a return value of -160 dB indicates minimum power" So does this mean this sound is at minimum power? I don't think this is true because the audio snippet is a fairly loud sound. I think I'm missing something here, any clarification would be appreciated.

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