ao_pipewire: Add PipeWire audio backend

Based-on-patch-by: Oschowa <oschowa@web.de>
Based-on-patch-by: Andreas Kempf <aakempf@gmail.com>

DOCS/man/ao.rst

@@ -144,6 +144,19 @@ Available audio output drivers are:
         Allow mpv to use PulseAudio even if the sink is suspended (default: no).
         Can be useful if PulseAudio is running as a bridge to jack and mpv has its sink-input set to the one jack is using.
 
+``pipewire``
+    PipeWire audio output driver
+
+    The following global options are supported by this audio output:
+
+    ``--pipewire-buffer-samples=<n>``
+        Set the audio buffer size in samples. A higher value buffers
+        more data, and has a lower probability of buffer underruns. A smaller
+        value makes the audio stream react faster, e.g. to playback speed
+        changes.
+        The effective size of the buffer depends on the amount of buffered
+        samples and the samplerate.
+
 ``sdl``
     SDL 1.2+ audio output driver. Should work on any platform supported by SDL
     1.2, but may require the ``SDL_AUDIODRIVER`` environment variable to be set

audio/out/ao.c

@@ -41,6 +41,7 @@ extern const struct ao_driver audio_out_audiounit;
 extern const struct ao_driver audio_out_coreaudio;
 extern const struct ao_driver audio_out_coreaudio_exclusive;
 extern const struct ao_driver audio_out_rsound;
+extern const struct ao_driver audio_out_pipewire;
 extern const struct ao_driver audio_out_pulse;
 extern const struct ao_driver audio_out_jack;
 extern const struct ao_driver audio_out_openal;
@@ -87,6 +88,9 @@ static const struct ao_driver * const audio_out_drivers[] = {
 #endif
 #if HAVE_SDL2_AUDIO
     &audio_out_sdl,
+#endif
+#if HAVE_PIPEWIRE
+    &audio_out_pipewire,
 #endif
     &audio_out_null,
 #if HAVE_COREAUDIO