[client] audio: add audio playback latency interface and graph

client/audiodevs/PipeWire/pipewire.c

@@ -370,6 +370,16 @@ static void pipewire_playbackMute(bool mute)
   pw_thread_loop_unlock(pw.thread);
 }
 
+static uint64_t pipewire_playbackLatency(void)
+{
+  const int frames = ringbuffer_getCount(pw.playback.buffer);
+  if (frames == 0)
+    return 0;
+
+  // TODO: we should really include the hw latency here too
+  return (uint64_t)pw.playback.sampleRate * 1000ULL / frames;
+}
+
 static void pipewire_recordStopStream(void)
 {
   if (!pw.record.stream)
@@ -527,11 +537,12 @@ struct LG_AudioDevOps LGAD_PipeWire =
   .free   = pipewire_free,
   .playback =
   {
-    .start  = pipewire_playbackStart,
-    .play   = pipewire_playbackPlay,
-    .stop   = pipewire_playbackStop,
-    .volume = pipewire_playbackVolume,
-    .mute   = pipewire_playbackMute
+    .start   = pipewire_playbackStart,
+    .play    = pipewire_playbackPlay,
+    .stop    = pipewire_playbackStop,
+    .volume  = pipewire_playbackVolume,
+    .mute    = pipewire_playbackMute,
+    .latency = pipewire_playbackLatency
   },
   .record =
   {

client/include/interface/audiodev.h

@@ -59,6 +59,9 @@ struct LG_AudioDevOps
 
     /* [optional] called to set muting of the output */
     void (*mute)(bool mute);
+
+    /* return the current total playback latency in microseconds */
+    uint64_t (*latency)(void);
   }
   playback;
 

client/src/audio.c

@@ -18,6 +18,7 @@
  * Temple Place, Suite 330, Boston, MA 02111-1307 USA
  */
 
+#include "audio.h"
 #include "main.h"
 #include "common/array.h"
 #include "common/util.h"
@@ -36,6 +37,10 @@ typedef struct
     int      volumeChannels;
     uint16_t volume[8];
     bool     mute;
+
+    LG_Lock     lock;
+    RingBuffer  timings;
+    GraphHandle graph;
   }
   playback;
 
@@ -60,6 +65,7 @@ void audio_init(void)
     if (LG_AudioDevs[i]->init())
     {
       audio.audioDev = LG_AudioDevs[i];
+      LG_LOCK_INIT(audio.playback.lock);
       DEBUG_INFO("Using AudioDev: %s", audio.audioDev->name);
       return;
     }
@@ -77,6 +83,7 @@ void audio_free(void)
 
   audio.audioDev->free();
   audio.audioDev = NULL;
+  LG_LOCK_FREE(audio.playback.lock);
 }
 
 bool audio_supportsPlayback(void)
@@ -84,6 +91,16 @@ bool audio_supportsPlayback(void)
   return audio.audioDev && audio.audioDev->playback.start;
 }
 
+static const char * audioGraphFormatFn(const char * name,
+    float min, float max, float avg, float freq, float last)
+{
+  static char title[64];
+  snprintf(title, sizeof(title),
+      "%s: min:%4.2f max:%4.2f avg:%4.2f now:%4.2f",
+      name, min, max, avg, last);
+  return title;
+}
+
 void audio_playbackStart(int channels, int sampleRate, PSAudioFormat format,
   uint32_t time)
 {
@@ -101,6 +118,8 @@ void audio_playbackStart(int channels, int sampleRate, PSAudioFormat format,
       return;
   }
 
+  LG_LOCK(audio.playback.lock);
+
   lastChannels   = channels;
   lastSampleRate = sampleRate;
   audio.playback.started = true;
@@ -116,6 +135,16 @@ void audio_playbackStart(int channels, int sampleRate, PSAudioFormat format,
   // set the inital mute state
   if (audio.audioDev->playback.mute)
     audio.audioDev->playback.mute(audio.playback.mute);
+
+  // if the audio dev can report it's latency setup a timing graph
+  if (audio.audioDev->playback.latency)
+  {
+    audio.playback.timings = ringbuffer_new(2400, sizeof(float));
+    audio.playback.graph   = app_registerGraph("PLAYBACK",
+        audio.playback.timings, 0.0f, 100.0f, audioGraphFormatFn);
+  }
+
+  LG_UNLOCK(audio.playback.lock);
 }
 
 void audio_playbackStop(void)
@@ -123,8 +152,18 @@ void audio_playbackStop(void)
   if (!audio.audioDev || !audio.playback.started)
     return;
 
+  LG_LOCK(audio.playback.lock);
+
   audio.audioDev->playback.stop();
   audio.playback.started = false;
+
+  if (audio.playback.timings)
+  {
+    app_unregisterGraph(audio.playback.graph);
+    ringbuffer_free(&audio.playback.timings);
+  }
+
+  LG_UNLOCK(audio.playback.lock);
 }
 
 void audio_playbackVolume(int channels, const uint16_t volume[])
@@ -244,3 +283,19 @@ void audio_recordMute(bool mute)
 
   audio.audioDev->record.mute(mute);
 }
+
+void audio_tick(unsigned long long tickCount)
+{
+  LG_LOCK(audio.playback.lock);
+  if (!audio.playback.timings)
+  {
+    LG_UNLOCK(audio.playback.lock);
+    return;
+  }
+
+  const uint64_t latency  = audio.audioDev->playback.latency();
+  const float    flatency = latency > 0 ? (float)latency / 1000.0f : 0.0f;
+  ringbuffer_push(audio.playback.timings, &flatency);
+
+  LG_UNLOCK(audio.playback.lock);
+}

client/src/audio.h

@@ -18,6 +18,9 @@
  * Temple Place, Suite 330, Boston, MA 02111-1307 USA
  */
 
+#include <stdbool.h>
+#include <purespice.h>
+
 void audio_init(void);
 void audio_free(void);
 
@@ -34,3 +37,5 @@ void audio_recordStart(int channels, int sampleRate, PSAudioFormat format);
 void audio_recordStop(void);
 void audio_recordVolume(int channels, const uint16_t volume[]);
 void audio_recordMute(bool mute);
+
+void audio_tick(unsigned long long tickCount);

client/src/main.c

@@ -155,6 +155,8 @@ static bool tickTimerFn(void * unused)
   if (needsRender)
     app_invalidateWindow(false);
 
+  audio_tick(tickCount);
+
   ++tickCount;
   return true;
 }