release-notes.txt
Sound multiplexing with ALSA
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Now, applications that use the ALSA api for playing sound will automatically use the dmix plugin by default on sound cards that do not support hardware mixing. Thus, such applications will always be able to play sound simultaneously.
Note that if an application uses the OSS emulation for playing sound with an ALSA driver, it'll get exclusive access to the sound card, thus excluding all other apps.
What's more, the dnsoop plugin is also set up, thus allowing several applications to record simultaneously from the same sound card
Last but not least, the softvol plugin is used for codecs without volume controls (eg: Azalia/intel HD audio) so that one can alter sound volume on cards that do not support it