Appendix: Audio library and drivers history

Audio library and drivers history

QNX has evolved through a series of different audio driver architectures each with their own strengths and weaknesses. Originally, QNX 4 provided the "Audio" driver series. In the late 1990's, this driver set was based on the BSD audio driver suite available as open source. This simple API was able to meet many application needs but fell short when attempting to implement complex multimedia applications.

In early 1999, the decision was made provide customers the option of using a new more powerful suite of audio drivers well suited for the multithreaded, DLL enabled QNX Neutrino 2 operating system. The Photon Team selected the best open source alternative at the time, the Advance Linux Sound Architecture (ALSA), then at version 0.13. Eventually this baseline was migrated to ALSA version 0.2. This is why some people refer to the ALSA 1 and ALSA 2 audio driver baselines interchangeably. Although the driver was multithreaded, it was modified to also run under the QNX 4 operating system. The ALSA baseline is available under the GNU Public License and is available in source code format from www.qnx.com in /usr/free/qnx4/multimedia/ALSA2.

The ALSA 2 drivers had two significant functional limitations:

A driver could only support one connection at a time
There's limited MIDI and sequencer support.

For this reason, QNX decided to upgrade to the ALSA v0.5.2 baseline, for the Neutrino 2 operating system.