RealTimeFileStreaming

Example of interfacing PortAudio real time audio with file I/O

This is example code for the paper:

Bencina, R. (2014) "Interfacing Real-Time Audio and File I/O," Proceedings of the 2014 Australasian Computer Music Conference, ACMC 2014. Melbourne, Australia. July 9-11 2014.

The paper and supporting materials are available at the following URL:

http://www.rossbencina.com/code/interfacing-real-time-audio-and-file-io

Status

The code works on OS X and Windows. It has been tested on Windows 7 with MSVC10 and OS X 10.7.5 with Xcode 4.6.1.

There's a little bit of work to do to get it working on Linux (replace Mach semaphore_t with sem_t). Maybe a bit more work to get it running on ARM (the interlocked exchange atomic primitive might need some work, not sure).

Source code overview

FileIoStreams.h/.cpp client stream objects for streaming data to or from a file. Lock-free and real-time safe.

FileIoRequest.h asynchronous message node object. Represents requests to, and replies from, the I/O server thread.

FileIoServer.h/.cpp file I/O server thread. Responds to FileIoRequests from client streams.

DataBlock.h buffer descriptor. Represents blocks of data read/written from/to a file. Pointers to DataBlocks are passed between server and client in FileIoRequest messages.

SharedBuffer.h/.cpp reference counted immutable shared buffer with lock-free cleanup. Used for storing file paths.

RecordAndPlayFileMain.cpp example real-time audio program that records and plays raw 16-bit stereo files.

How to build and run the example

At the moment there are project files for Windows MSVC10 and OS X (Xcode 4.6 or later). Help with Linux would be welcome.

1. Check out the sources and the dependencies:

git clone https://github.com/RossBencina/RealTimeFileStreaming.git
git clone -b C++03-legacy https://github.com/RossBencina/QueueWorld.git
git clone https://github.com/mintomic/mintomic.git
svn co https://subversion.assembla.com/svn/portaudio/portaudio/trunk/ portaudio

You should now have the following directories:

 RealTimeFileStreaming/
 QueueWorld/
 mintomic/
 portaudio/

[Note: this example code uses the C++03 version of QueueWorld. The C++11 version of QueueWorld is currently untested with this RealTimeFileStreaming example code.]

2. Open the project.

• On Windows, with MSVC2010 or later, navigate to RealTimeFileStreaming\build\msvs10\RealTimeFileStreaming and open the Visual Studio solution file RealTimeFileStreaming.sln
• On OS X, with Xcode 4.6 or later, navigate to RealTimeFileStreaming\build\xcode4.6\RealTimeFileStreaming and open the Xcode project RealTimeFileStreaming.xcodeproj

3. Set up audio file paths. The example program references two file paths: playbackFilePath for playing an existing file and recordTestFilePath for playing and recording a test file. These are both declared in main() in RecordAndPlayFileMain.cpp. You need to edit their values to refer to valid file paths on your system (don't forget to escape backslashes if you're on Windows). The example code only reads headerless 16-bit stereo files (44.1k for the default settings).

• For playbackFilePath you either need to create a file of the appropriate format, or you can grab this file: https://www.dropbox.com/s/ec923lzkr9udxww/171326__bradovic__piano-improvisation.dat [1].
• The recordTestFilePath file should be a valid path on your system, but the file should not exist. It will be created or overwritten every time you start recording from within the test program. Just make sure that the directory portion of the path exists.

4. Run the project. It should build and run, playing a sine wave. There are instructions on the screen for starting and stopping recording and playback. It will work for recording and playing a new test file (recordTestFilePath) even if you don't have the playbackFilePath file set up correctly.

[1] File credit: Bradovic at freesound.org https://www.freesound.org/people/Bradovic/sounds/171326/ (CC-Zero).