[client] audio: add transport provider interface

Route audio through a provider interface. Connected transports take
priority while SPICE remains the fallback.

Carry explicit sample formats, rates, channel layouts, and source clocks
through playback and recording. Add optional presentation clock feedback
for active synchronization.

client/audiodevs/PulseAudio/pulseaudio.c

@@ -42,8 +42,7 @@ struct PulseAudio
   bool                   sinkStarting;
   int                    sinkMaxPeriodFrames;
   int                    sinkStartFrames;
-  int                    sinkSampleRate;
-  int                    sinkChannels;
+  LG_AudioFormat         sinkFormat;
   int                    sinkStride;
   LG_AudioPullFn         sinkPullFn;
   _Atomic(int64_t)       sinkPresentationDeadline;
@@ -51,6 +50,68 @@ struct PulseAudio
 
 static struct PulseAudio pa = {0};
 
+static bool pulseaudio_audioFormatEqual(const LG_AudioFormat * a,
+    const LG_AudioFormat * b)
+{
+  return
+    a->sampleFormat == b->sampleFormat &&
+    a->sampleRate   == b->sampleRate &&
+    a->channelCount == b->channelCount &&
+    memcmp(a->channels, b->channels,
+        a->channelCount * sizeof(*a->channels)) == 0;
+}
+
+static pa_channel_position_t pulseaudio_channel(
+    LG_AudioChannel channel, uint8_t index)
+{
+  switch (channel)
+  {
+    case LG_AUDIO_CH_UNKNOWN:
+      return (pa_channel_position_t)(PA_CHANNEL_POSITION_AUX0 + index);
+
+    case LG_AUDIO_CH_MONO               :
+      return PA_CHANNEL_POSITION_MONO;
+    case LG_AUDIO_CH_FRONT_LEFT         :
+      return PA_CHANNEL_POSITION_FRONT_LEFT;
+    case LG_AUDIO_CH_FRONT_RIGHT        :
+      return PA_CHANNEL_POSITION_FRONT_RIGHT;
+    case LG_AUDIO_CH_FRONT_CENTER       :
+      return PA_CHANNEL_POSITION_FRONT_CENTER;
+    case LG_AUDIO_CH_LFE                :
+      return PA_CHANNEL_POSITION_LFE;
+    case LG_AUDIO_CH_REAR_LEFT          :
+      return PA_CHANNEL_POSITION_REAR_LEFT;
+    case LG_AUDIO_CH_REAR_RIGHT         :
+      return PA_CHANNEL_POSITION_REAR_RIGHT;
+    case LG_AUDIO_CH_FRONT_LEFT_CENTER  :
+      return PA_CHANNEL_POSITION_FRONT_LEFT_OF_CENTER;
+    case LG_AUDIO_CH_FRONT_RIGHT_CENTER :
+      return PA_CHANNEL_POSITION_FRONT_RIGHT_OF_CENTER;
+    case LG_AUDIO_CH_REAR_CENTER        :
+      return PA_CHANNEL_POSITION_REAR_CENTER;
+    case LG_AUDIO_CH_SIDE_LEFT          :
+      return PA_CHANNEL_POSITION_SIDE_LEFT;
+    case LG_AUDIO_CH_SIDE_RIGHT         :
+      return PA_CHANNEL_POSITION_SIDE_RIGHT;
+    case LG_AUDIO_CH_TOP_CENTER         :
+      return PA_CHANNEL_POSITION_TOP_CENTER;
+    case LG_AUDIO_CH_TOP_FRONT_LEFT     :
+      return PA_CHANNEL_POSITION_TOP_FRONT_LEFT;
+    case LG_AUDIO_CH_TOP_FRONT_CENTER   :
+      return PA_CHANNEL_POSITION_TOP_FRONT_CENTER;
+    case LG_AUDIO_CH_TOP_FRONT_RIGHT    :
+      return PA_CHANNEL_POSITION_TOP_FRONT_RIGHT;
+    case LG_AUDIO_CH_TOP_REAR_LEFT      :
+      return PA_CHANNEL_POSITION_TOP_REAR_LEFT;
+    case LG_AUDIO_CH_TOP_REAR_CENTER    :
+      return PA_CHANNEL_POSITION_TOP_REAR_CENTER;
+    case LG_AUDIO_CH_TOP_REAR_RIGHT     :
+      return PA_CHANNEL_POSITION_TOP_REAR_RIGHT;
+  }
+
+  return (pa_channel_position_t)(PA_CHANNEL_POSITION_AUX0 + index);
+}
+
 static void pulseaudio_unrefOperation(pa_operation * operation)
 {
   if (operation)
@@ -299,14 +360,17 @@ static void pulseaudio_overflow_cb(pa_stream * p, void * userdata)
   DEBUG_WARN("Overflow");
 }
 
-static bool pulseaudio_setup(int channels, int sampleRate,
+static bool pulseaudio_setup(const LG_AudioFormat * format,
     int requestedPeriodFrames, bool requestResampler,
     bool * resamplerEnabled, int * maxPeriodFrames, int * startFrames,
     LG_AudioPullFn pullFn)
 {
   *resamplerEnabled = false;
 
-  if (pa.sink && pa.sinkChannels == channels && pa.sinkSampleRate == sampleRate)
+  const int channels   = format->channelCount;
+  const int sampleRate = format->sampleRate;
+
+  if (pa.sink && pulseaudio_audioFormatEqual(&pa.sinkFormat, format))
   {
     *maxPeriodFrames = pa.sinkMaxPeriodFrames;
     *startFrames     = pa.sinkStartFrames;
@@ -318,6 +382,9 @@ static bool pulseaudio_setup(int channels, int sampleRate,
     .rate     = sampleRate,
     .channels = channels
   };
+  pa_channel_map channelMap = { .channels = channels };
+  for (uint8_t i = 0; i < format->channelCount; ++i)
+    channelMap.map[i] = pulseaudio_channel(format->channels[i], i);
 
   int stride = channels * sizeof(float);
   int bufferSize = requestedPeriodFrames * 2 * stride;
@@ -332,14 +399,14 @@ static bool pulseaudio_setup(int channels, int sampleRate,
   pa_threaded_mainloop_lock(pa.loop);
   pulseaudio_sink_close_nl();
 
-  pa.sinkChannels   = channels;
-  pa.sinkSampleRate = sampleRate;
-  pa.sinkStride     = stride;
-  pa.sinkPullFn     = pullFn;
-  pa.sinkCorked     = true;
-  pa.sinkStarting   = false;
+  pa.sinkFormat   = *format;
+  pa.sinkStride   = stride;
+  pa.sinkPullFn   = pullFn;
+  pa.sinkCorked   = true;
+  pa.sinkStarting = false;
 
-  pa.sink = pa_stream_new(pa.context, "Looking Glass", &spec, NULL);
+  pa.sink = pa_stream_new(
+      pa.context, "Looking Glass", &spec, &channelMap);
   if (!pa.sink)
   {
     DEBUG_ERROR("Failed to create PulseAudio stream: %s",