ao_oss: add this audio output again

Changes:
- code refactored;
- mixer options removed;
- new mpv sound API used;
- add sound devices detect (mpv --audio-device=help will show all available devices);
- only OSSv4 supported now;

Tested on FreeBSD 12.2 amd64.

1 files changed, 4 insertions, 1 deletions

diff --git a/DOCS/man/ao.rst b/DOCS/man/ao.rst
index d70286647f..1c0b9e146b 100644
--- a/DOCS/man/ao.rst
+++ b/DOCS/man/ao.rst
@@ -14,7 +14,7 @@ in the list.
 
     See ``--ao=help`` for a list of compiled-in audio output drivers. The
     driver ``--ao=alsa`` is preferred. ``--ao=pulse`` is preferred on systems
-    where PulseAudio is used.
+    where PulseAudio is used. On BSD systems, ``--ao=oss`` is preferred.
 
 Available audio output drivers are:
 
@@ -35,6 +35,9 @@ Available audio output drivers are:
         with automatic upmixing with shared access, so playing stereo
         and multichannel audio at the same time will work as expected.
 
+``oss``
+    OSS audio output driver
+
 ``jack``
     JACK (Jack Audio Connection Kit) audio output driver.