Recently something happened – when starting guest-os, I got error saying “No audio devices could be opened” :
and in log was such data:
00:00:05.542 Audio: Trying driver 'alsa'. 00:00:05.595 ALSA: Failed to apply audio parameters 00:00:05.595 HDAcodec: can't open in fmt(freq: 44100) 00:00:05.602 ALSA: Failed to apply audio parameters 00:00:05.608 ALSA: Failed to apply audio parameters 00:00:05.608 HDA: WARNING: Unable to open PCM IN! 00:00:05.608 HDA: WARNING: Unable to open PCM OUT! 00:00:05.608 Audio: Using NULL audio driver 00:00:05.608 VM: Raising runtime error 'HostAudioNotResponding' (fFlags=0x0) 00:00:05.608 Console: VM runtime error: fatal=false, errorID=HostAudioNotResponding message="No audio devices could be opened. Selecting the NULL audio backend with the consequence that no sound is audible"
It turns out, that there is conflict between how different software needs/wants to use some library. Although at first it seems, that problem is on gentoo’s and libsdl’s side, it is VirtualBox’es thing to fix.
Until it is not fixxed, one solution is not to use latest libsdl. Just add to /etc/portage/package.mask/monolithic following line:
and reemerge media-libs/libsdl package