AAC のハードウェアエンコーダーをサポートしているかどうかのチェック。

gistfile1.m

- (BOOL)isAACHardwareEncoderAvailable
{
    OSStatus status;
    UInt32   size;;
    UInt32   encoderSpecifier = kAudioFormatMPEG4AAC;
    status = AudioFormatGetPropertyInfo(kAudioFormatProperty_Encoders,
                                        sizeof(encoderSpecifier),
                                        &encoderSpecifier,
                                        &size);
    check_osstatus(status, @"AudioFormatGetPropertyInfo fail");
    if(status != noErr){
        return NO;
    }

    UInt32 numEncodres = size / sizeof(AudioClassDescription);
    AudioClassDescription encoderDescriptions[numEncodres];
    status = AudioFormatGetProperty(kAudioFormatProperty_Encoders,
                                    sizeof(encoderSpecifier),
                                    &encoderSpecifier,
                                    &size,
                                    encoderDescriptions);
    check_osstatus(status, @"AudioFormatGetProperty fail");
    if(status != noErr){
        return NO;
    }
    
    for(int i=0; i<numEncodres; ++i){
        AudioClassDescription desc = encoderDescriptions[i];
        if(desc.mSubType == kAudioFormatMPEG4AAC &&
           desc.mManufacturer == kAppleHardwareAudioCodecManufacturer){
            return YES;
        }
    }
    return NO;
}