Audacity PortAudio v19

Windows
PortAudio appears to be stable and relatively well behaved on Windows. Audacity has always supported MME (Multi Media Extensions) drivers and added support for Windows DirectSound devices from legacy Audacity Beta 1.3.7 onwards. Audacity is capable of ASIO support but this is not shipped in Audacity releases, as discussed on the ASIO Audio Interface page.

PortAudio doesn't support 24-bit recording on MME or Windows DirectSound, but from Audacity 2.0.4 onwards, current Audacity releases support 24-bit recording under Windows WASAPI and Windows WDM-KS (assuming 24-bit capable hardware).

Mac OS X
Only CoreAudio is supported. Some changes to PortAudio v19 appeared to be causing regressions for a time, and until recent updates v19 worked much less well that v18 with many USB audio devices. PortAudio v19 has always worked better than v18 with Firewire audio devices (which are quite popular on Mac it seems).

Audacity supports 24-bit recording under CoreAudio (assuming 24-bit capable hardware).

A shortage of Mac developers on Audacity sometimes means slow progress in testing and development.

Linux

 * ALSA is supported and works fine on development systems, although some distributions repeatedly report problems that don't show up anywhere else. Audacity supports 24-bit recording under ALSA (assuming 24-bit capable hardware).
 * JACK support has improved with the 2.0.x series of Audacity, with some known issues - see the JACK section of our Linux Issues page for more detail. Help, especially patches to fix issues would be much appreciated. Audacity supports 24-bit recording under JACK (assuming 24-bit capable hardware).
 * There is no PulseAudio back-end to PortAudio, so historically it was necessary to suspend PulseAudio or rely on PulseAudio providing some sort of emulation. However PortAudio support for PulseAudio has improved to the extent that Audacity can now recognize a working pulse device. However for best results it is recommended to install the PulseAudio Volume Control (pavucontrol).
 * OSS works from historical reports but is no longer actively tested. Using the OSS emulation over ALSA is not recommended because it has problems with cursor movement for some cards. Use the native ALSA interface instead.