Calibrate prepared audio from silent callback timestamps

roadscore/prototype/mac_showcase.py

@@ -222,6 +222,7 @@ def audio_worker(a):
   done = False
   errors = []
   clock_errors = []
+  clock_observations = []
   bridge = None
   flags = 0
   max_drift = 0.
@@ -231,7 +232,11 @@ def audio_worker(a):
   def callback(out, n, ti, status):
     nonlocal position,rendered,done,flags,max_drift,first_frame,callback_revision
     out.fill(0)
-    if anchor is None or bridge is None or done:return
+    if bridge is None:
+      if len(clock_observations)<24:
+        clock_observations.append((float(time.monotonic()),float(ti.currentTime),float(ti.outputBufferDacTime)))
+      return
+    if anchor is None or done:return
     now=time.monotonic()
     active_anchor=anchor
     expected=None;dac=None;start=position
@@ -266,7 +271,14 @@ def audio_worker(a):
       server = control_server(a.project_root,a.out,shared,a.port,forwarder,follow_peer=forwarder is not None)
       write_json(a.out/'controls.json',{'url':f'http://127.0.0.1:{server.server_port}/'})
     with sd.OutputStream(device=a.audio_device,samplerate=rate,channels=2,blocksize=960,dtype='float32',callback=callback) as stream:
-      bridge=StreamClockBridge.measure(lambda:stream.time)
+      calibration_deadline=time.monotonic()+2.
+      while len(clock_observations)<20:
+        if not stream.active:raise RuntimeError('Output stream stopped during silent clock calibration')
+        if time.monotonic()>=calibration_deadline:raise TimeoutError('Output clock did not provide 20 silent callbacks')
+        time.sleep(.01)
+      observations=list(clock_observations[:20])
+      write_json(a.out/'stream_clock_calibration.json',dict(silent_callback_samples=observations))
+      bridge=StreamClockBridge.from_callbacks(observations)
       (a.out/'prepared_ready').write_text('ready')
       while not done:
         sm.update(50);now=time.monotonic();controls.poll()

roadscore/prototype/test_replay_sync.py

@@ -120,9 +120,21 @@ class ReplaySyncTests(unittest.TestCase):
                  playback_clock=PreparedClock(),audio=np.zeros((480000,2),np.float32),
                  processor=SimpleNamespace(process=lambda chunk,*args:(chunk,{})),state={},
                  controls=SimpleNamespace(selection=('recorded','recorded')),a=SimpleNamespace(muted=True),
-                 errors=[],clock_errors=[])
+                 errors=[],clock_errors=[],clock_observations=[])
     exec(compile(ast.Module(body=[callback],type_ignores=[]),str(path),'exec'),context)
     out=np.ones((960,2),np.float32)
+    # Startup gathers only a bounded set of silent observations. No stream.time
+    # getter, model anchor, source-frame processing or output is required.
+    saved_bridge=context['bridge'];context['bridge']=None
+    for i in range(30):
+      context['time'].monotonic=lambda i=i:99.+i*.02
+      context['callback'](out,960,SimpleNamespace(currentTime=499.+i*.02,outputBufferDacTime=499.04+i*.02),False)
+      self.assertFalse(out.any())
+    self.assertEqual(len(context['clock_observations']),24)
+    self.assertIsNone(context['position'])
+    calibrated=StreamClockBridge.from_callbacks(context['clock_observations'][:20])
+    self.assertAlmostEqual(calibrated.offset,-400.)
+    context['bridge']=saved_bridge;context['time'].monotonic=lambda:100.08
     context['callback'](out,960,SimpleNamespace(currentTime=500.,outputBufferDacTime=500.056),False)
     context['time'].monotonic=lambda:100.04
     context['callback'](out,960,SimpleNamespace(currentTime=500.02,outputBufferDacTime=500.076),False)