How to resolve "Hardware In Use" issue (error code: 'hwiu')?

I have created an iPhone app with recording with AudioUnit, Conversion, Audio Editing and Merging parts. I done everything except Conversion. This app will work only in iOS 4 or higher.

I tried to convert .caf to .m4a file. But I am getting kAudioConverterErr_HardwareInUse error. Then I tried to convert .caf file to .wav file. Then .wav file to .m4a file. But I am getting the same issue.

I am not clear with this issue. In the Apple documentation, they mentioned like ;

"Returned from the AudioConverterFillComplexBuffer function if the underlying hardware codec has become unavailable, 开发者_如何学Pythonprobably due to an audio interruption.

On receiving this error, your application must stop calling AudioConverterFillComplexBuffer. You can check the value of the kAudioConverterPropertyCanResumeFromInterruption property to determine if the converter you are using can resume processing after an interruption. If so, then wait for an interruption-ended call from Audio Session Services, reactivate the audio session, and finally resume using the codec.

If the converter cannot resume processing after an interruption, then on interruption you must abandon the conversion, re-instantiate the converter, and perform the conversion again."

Please help me to resolve it.

I just resolved such a problem. In my case, I have MPMoviePlayerController, audio queue player, audio recorder in the application.

the movie player needs manually calling "stop" method when content ends. Otherwise the play state is lock at MPMoviePlaybackStatePlaying. Then I can no more play MP3 and get "hwiu" when I try it. But PCM still work.

Maybe it's because the compressed audio (MP3, AAC, ...) is handled by a unique hardware device. If you are using different techniques (MPMoviePlayerController and audio queue service) to playback compressed audio, you need to release the device once after you finish playing since they are all share the same device.