** HOW TO USE **

Within an Xcode project that uses this class, make sure that you have included CoreMedia.framework and AudioToolbox.framework.

Simply initialize this interface in an Objective-C++ class, and set a delegate that implements one or more of the Objective-C methods defined by the protocol "NLRemoteIOAudioPlayerDelegate" before calling any functions within.

NLRemoteIOAudioPlayer* audioPlayer = new NLRemoteIOAudioPlayer(); audioPlayer->_delegate = anInputController;

As with all Objective-C delegates, you need only add a simple definition to your Objective-C class's defined interface, for example;

@interface MyViewController : UIViewController

Feel free to define the following methods in your class delegate to implement the following functionality;

• (void) updateViewForRemoteIOAudioPlayerState;
• (void) updateViewForRemoteIOAudioPlayerDuration;
• (void) rioPlaybackDidEnd;
• (void) updateViewForRemoteIOAudioPlayerAlbumInfo;

All of these methods suggest an update to your UI, and the methods themselves will be called asynchronously on your app's main Grand Central Dispatch queue.

To play audio, you need only provide a reference to an audio file that you want to play back, like so;

NSURL *pathToFile = [ NSURL URLWithString: [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"music.mp4"]];

audioPlayer->startRioUnitWithInputURL( (CFURLRef) pathToFile );

Then it will automatically start streaming the audio, with a very tiny memory footprint.

While it's playing, you can control playback with the following functions;

audioPlayer->stopRioUnit(); // to pause audio audioPlayer->startRioUnit(); // to resume playback after pausing

You can also seek to a different playback position in the file, given an input of type "float" where "0.0" indicates the very beginning of the file, and the value provided by NLRemoteIOAudioPlayer's "getFileDurationInSeconds()" method indicates the end of the file.

audioPlayer->seekToPosition(0.0);

There is also a function that returns a boolean value to indicate the state of playback, which can be queried as follows;

audioPlayer->isPlaying();

More information on the last frame buffered by the file and the sample rate of the Audio Unit can be provided by the getFramesBuffered() method, within its "value" property, contained within a CMTime structure. You can also find out how many frames there are in the entire file with getFileDuration()'s "value" property, which is also contained in a CMTime structure.

For these CMTime structures, the "timescale" property from getFramesBuffered() is equivalent to the Audio Unit's sample rate, while getFileDuration() contains the file's sample rate. To convert these frame measurements to equivalent, user- friendly seconds, simply divide the value by its corresponding timescale.

This source code is offered under the MIT license, but portions are derived from Apple Inc.'s MixerHost sample code. Apple Inc.'s original license is attached within the source code wherever it is applicable.

The MIT License

Copyright (c) 2010 Thames Galley Software

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.