AKBP-II 1997: Group 5

Audio Multiplexing Devicedriver for Solaris 2.5

Unfortunately we have not yet prepared an elaborate English version of this page. If you don't know German, you will have to make do with this short description... (In fact, this English version was just created out of curiosity about how this multilingual-HTML-feature works).

In short, our device driver:

• offers replacement /dev/audio and /dev/audioctl to existing applications. These are streams-based ``clone-devices'' like /dev/ip etc. The effect is that several applications can access /dev/audio at the same time without blocking.
• converts incoming data to 44.1kHz, 16bit linear, stereo data format and
• forwards the data, mixed with the appropriate volume levels, to the ``original'' /dev/audio
• is accompanied by a graphical tool, ``audioctl'', which controls the mixing process (volume levels) and displays the names of the processes which have openened /dev/audio or /dev/audioctl. It is also used to control the ``original'' /dev/audioctl (to set the global volume level or balance). Cf. the screenshot following the text.

Missing in the current implementation is:

• support for recording (difficult; the best way would probably be to emulate the behaviour of /dev/audio, i.e. block conflicting requests until the resource becomes available)
• code for conversion of A-law and linear data at sampling rates other than 44.1kHz, 16bit, stereo (both of which could easily be added, should the need arise)
• optimization of the mixing process (might not be possible without sacrificing the elegant structure of the program) -- currently the driver seems to be useful only for workstations upwards of SUN SS20s.

Bernhard Rümenapp, bdruemen@cip.informatik.uni-erlangen.de
and Christoph Windpassinger, windpassinger@informatik.uni-erlangen.de