Failed to setup audio file in apple sample code "AVCaptureToAudioUnit"

I am unfamiliar with Objective-C and audioUnit.

I want to make the iOS app which can save the audio signal from the microphone through some audioUnit effects that sound in the device. so now I am trying to study apple's sample code "AVCaptureToAudioUnit"

https://developer.apple.com/library/ios/samplecode/AVCaptureToAudioUnit/Introduction/Intro.html (build with Xcode 6.1 and simulator iphone5.)

but It exposed the error below

AudioStreamBasicDescription: 0 ch,0 Hz,'lpcm' (0x0000000E) 16-bit signed integer

2015-03-17 13:44:56.589 AVCaptureToAudioUnit[1462:151210] Failed to setup audio file! (29759)

these logs written in method of CaptureSessionController.mm below

- (void)startRecording
{
 if (!self.isRecording) {
    OSErr err = kAudioFileUnspecifiedError;
    @synchronized(self) {
        if (!extAudioFile) {
            /*
             Start recording by creating an ExtAudioFile and configuring it with the same sample rate and
             channel layout as those of the current sample buffer.
            */

            // recording format is the format of the audio file itself
            CAStreamBasicDescription recordingFormat(currentInputASBD.mSampleRate,
                                                     currentInputASBD.mChannelsPerFrame,
                                                     CAStreamBasicDescription::kPCMFormatInt16,
                                                     true);
            recordingFormat.mFormatFlags |= kAudioFormatFlagIsBigEndian;

            NSLog(@"Recording Audio Format:");
            recordingFormat.Print();

            err = ExtAudioFileCreateWithURL(_outputFile,
                                            kAudioFileAIFFType,
                                            &recordingFormat,
                                            currentRecordingChannelLayout,
                                            kAudioFileFlags_EraseFile,
                                            &extAudioFile);
            if (noErr == err)
                // client format is the output format from the delay unit
                err = ExtAudioFileSetProperty(extAudioFile,
                                              kExtAudioFileProperty_ClientDataFormat,
                                              sizeof(graphOutputASBD),
                                              &graphOutputASBD);

            if (noErr != err) {
                if (extAudioFile) ExtAudioFileDispose(extAudioFile);
                extAudioFile = NULL;
            }
        }
    } // @synchronized

    if (noErr == err) {
        self.recording = YES;
        NSLog(@"Recording Started");
    } else {
        NSLog(@"Failed to setup audio file! (%ld)", (long)err);
    }
}
}

it seems that the extraction of "currentInputASBD" don't work, but I couldn't find the solution for myself. If anyone knows how to fix this issue and share it , I highly appreciate.

best regards.

dubryu

AudioStreamBasicDescription: 0 ch,0 Hz,'lpcm' (0x0000000E) 16-bit signed integer

One problem is that you have not specified the number-of-channels (see 0 ch). So you need to specify it.

You should see something similar to:

AudioStreamBasicDescription: 1 ch, 44100 Hz, 'lpcm' (0x0000000E) 16-bit signed integer