webrtcdsp: Add delay-agnostic property

In this mode, we let WebRTC Audio Processing figure-out the delay. This
is useful when the latency reported by the stack cannot be trusted. Note
that in this mode, the leaking of echo during packet lost is much worst.
It is recommanded to use PLC (e.g. spanplc, or opus built-in plc).

In this mode, we don't do any synchronization. Instead, we simply process all
the available reverse stream data as it comes.

ext/webrtcdsp/gstwebrtcdsp.cpp

@@ -156,7 +156,8 @@ enum
   PROP_NOISE_SUPPRESSION_LEVEL,
   PROP_GAIN_CONTROL,
   PROP_EXPERIMENTAL_AGC,
-  PROP_EXTENDED_FILTER
+  PROP_EXTENDED_FILTER,
+  PROP_DELAY_AGNOSTIC
 };
 
 /**
@@ -189,6 +190,7 @@ struct _GstWebrtcDsp
   gboolean gain_control;
   gboolean experimental_agc;
   gboolean extended_filter;
+  gboolean delay_agnostic;
 };
 
 G_DEFINE_TYPE (GstWebrtcDsp, gst_webrtc_dsp, GST_TYPE_AUDIO_FILTER);
@@ -290,8 +292,11 @@ gst_webrtc_dsp_analyze_reverse_stream (GstWebrtcDsp * self,
 
   apm = self->apm;
 
-  delay = gst_webrtc_echo_probe_read (probe, rec_time, (gpointer) &frame);
+  if (self->delay_agnostic)
+    rec_time = GST_CLOCK_TIME_NONE;
 
+again:
+  delay = gst_webrtc_echo_probe_read (probe, rec_time, (gpointer) &frame);
   apm->set_stream_delay_ms (delay);
 
   if (delay < 0)
@@ -310,6 +315,9 @@ gst_webrtc_dsp_analyze_reverse_stream (GstWebrtcDsp * self,
     GST_WARNING_OBJECT (self, "Reverse stream analyses failed: %s.",
         webrtc_error_to_string (err));
 
+  if (self->delay_agnostic)
+      goto again;
+
 done:
   gst_object_unref (probe);
 
@@ -401,6 +409,8 @@ gst_webrtc_dsp_start (GstBaseTransform * btrans)
       (new webrtc::ExtendedFilter (self->extended_filter));
   config.Set < webrtc::ExperimentalAgc >
       (new webrtc::ExperimentalAgc (self->experimental_agc));
+  config.Set < webrtc::DelayAgnostic >
+      (new webrtc::DelayAgnostic (self->delay_agnostic));
 
   /* TODO Intelligibility enhancer, Beamforming, etc. */
 
@@ -590,6 +600,9 @@ gst_webrtc_dsp_set_property (GObject * object,
     case PROP_EXTENDED_FILTER:
       self->extended_filter = g_value_get_boolean (value);
       break;
+    case PROP_DELAY_AGNOSTIC:
+      self->delay_agnostic = g_value_get_boolean (value);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -632,6 +645,9 @@ gst_webrtc_dsp_get_property (GObject * object,
     case PROP_EXTENDED_FILTER:
       g_value_set_boolean (value, self->extended_filter);
       break;
+    case PROP_DELAY_AGNOSTIC:
+      g_value_set_boolean (value, self->delay_agnostic);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -761,6 +777,13 @@ gst_webrtc_dsp_class_init (GstWebrtcDspClass * klass)
           "Enable or disable the extended filter.",
           TRUE, (GParamFlags) (G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS |
               G_PARAM_CONSTRUCT)));
+
+  g_object_class_install_property (gobject_class,
+      PROP_DELAY_AGNOSTIC,
+      g_param_spec_boolean ("delay-agnostic", "Delay Agnostic",
+          "Enable or disable the delay agnostic mode.",
+          FALSE, (GParamFlags) (G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS |
+              G_PARAM_CONSTRUCT)));
 }
 
 static gboolean

ext/webrtcdsp/gstwebrtcechoprobe.cpp

@@ -280,6 +280,20 @@ gst_webrtc_echo_probe_read (GstWebrtcEchoProbe * self, GstClockTime rec_time,
   if (!GST_CLOCK_TIME_IS_VALID (self->latency))
     goto done;
 
+  /* In delay agnostic mode, just return 10ms of data */
+  if (!GST_CLOCK_TIME_IS_VALID (rec_time)) {
+    avail = gst_adapter_available (self->adapter);
+
+    if (avail < self->period_size)
+      goto done;
+
+    size = self->period_size;
+    skip = 0;
+    offset = 0;
+
+    goto copy;
+  }
+
   if (gst_adapter_available (self->adapter) == 0) {
     diff = G_MAXINT64;
   } else {
@@ -317,6 +331,7 @@ gst_webrtc_echo_probe_read (GstWebrtcEchoProbe * self, GstClockTime rec_time,
   if (size < self->period_size)
     memset (frame->data_, 0, self->period_size);
 
+copy:
   if (size) {
     gst_adapter_copy (self->adapter, (guint8 *) frame->data_ + skip,
         offset, size);