From 8710c3946256900f1873922873599a9594895508 Mon Sep 17 00:00:00 2001
From: borine <32966433+borine@users.noreply.github.com>
Date: Mon, 23 Dec 2024 11:20:59 +0000
Subject: [PATCH] Filter internal delay D-Bus signals

Only emit D-Bus delay signal for internal processing delays if the
change is >= 10ms
---
 src/ba-transport-pcm.c | 69 ++++++++++++++++++++++++++++--------------
 src/ba-transport-pcm.h |  3 ++
 2 files changed, 49 insertions(+), 23 deletions(-)

diff --git a/src/ba-transport-pcm.c b/src/ba-transport-pcm.c
index d9306aa14..18c36198d 100644
--- a/src/ba-transport-pcm.c
+++ b/src/ba-transport-pcm.c
@@ -750,35 +750,58 @@ int ba_transport_pcm_delay_get(const struct ba_transport_pcm *pcm) {
 int ba_transport_pcm_delay_sync(struct ba_transport_pcm *pcm, unsigned int update_mask) {
 
 	struct ba_transport *t = pcm->t;
-	int delay = 0;
-
-	delay += pcm->codec_delay_dms;
-	delay += pcm->processing_delay_dms;
-	delay += pcm->client_delay_dms;
 
 	/* In case of A2DP Sink, update the delay property of the BlueZ media
 	 * transport interface. BlueZ should forward this value to the remote
 	 * device, so it can adjust audio/video synchronization. */
-	if (t->profile == BA_TRANSPORT_PROFILE_A2DP_SINK &&
-			t->a2dp.delay_reporting &&
-			abs(delay - t->a2dp.delay) >= 100 /* 10ms */) {
-
-		GError *err = NULL;
-		t->a2dp.delay = delay;
-		g_dbus_set_property(config.dbus, t->bluez_dbus_owner, t->bluez_dbus_path,
-				BLUEZ_IFACE_MEDIA_TRANSPORT, "Delay", g_variant_new_uint16(delay), &err);
-
-		if (err != NULL) {
-			if (err->code == G_DBUS_ERROR_PROPERTY_READ_ONLY)
-				/* Even though BlueZ documentation says that the Delay property is
-				 * read-write, it might not be true. In case when the delay write
-				 * operation fails with "not writable" error, we should not try to
-				 * update the delay report value any more. */
-				t->a2dp.delay_reporting = false;
-			warn("Couldn't set A2DP transport delay: %s", err->message);
-			g_error_free(err);
+	if (t->profile == BA_TRANSPORT_PROFILE_A2DP_SINK) {
+
+		int delay = 0;
+		delay += pcm->codec_delay_dms;
+		delay += pcm->processing_delay_dms;
+		delay += pcm->client_delay_dms;
+
+		if (t->a2dp.delay_reporting &&
+					abs(delay - t->a2dp.delay) >= 100 /* 10ms */) {
+
+			GError *err = NULL;
+			t->a2dp.delay = delay;
+			g_dbus_set_property(config.dbus, t->bluez_dbus_owner,
+					t->bluez_dbus_path, BLUEZ_IFACE_MEDIA_TRANSPORT, "Delay", g_variant_new_uint16(delay), &err);
+
+			if (err != NULL) {
+				if (err->code == G_DBUS_ERROR_PROPERTY_READ_ONLY)
+					/* Even though BlueZ documentation says that the Delay
+					 * property is read-write, it might not be true. In case
+					 * when the delay write operation fails with "not writable"
+					 * error, we should not try to update the delay report
+					 * value any more. */
+					t->a2dp.delay_reporting = false;
+				warn("Couldn't set A2DP transport delay: %s", err->message);
+				g_error_free(err);
+			}
+
 		}
+	}
 
+	/* If the remote device does not provide delay update reports we can still
+	 * inform local D-Bus clients of our internal processing delay. */
+	if ((t->profile & BA_TRANSPORT_PROFILE_MASK_A2DP) == 0 ||
+				!t->a2dp.delay_reporting) {
+
+		if (update_mask == BA_DBUS_PCM_UPDATE_DELAY) {
+
+			/* To avoid creating a flood of dbus signals, we only notify clients
+			 * when the codec + processing value changes by more than 10ms */
+			unsigned int delay = pcm->codec_delay_dms + pcm->processing_delay_dms;
+			unsigned int diff = delay >= pcm->reported_codec_delay_dms ?
+					delay - pcm->reported_codec_delay_dms :
+					pcm->reported_codec_delay_dms - delay;
+			if (diff >= 100 /* 10ms */)
+				pcm->reported_codec_delay_dms = delay;
+			else
+				return 0;
+		}
 	}
 
 	/* Notify all connected D-Bus clients. */
diff --git a/src/ba-transport-pcm.h b/src/ba-transport-pcm.h
index acd1e9d85..7ff4f436c 100644
--- a/src/ba-transport-pcm.h
+++ b/src/ba-transport-pcm.h
@@ -129,6 +129,9 @@ struct ba_transport_pcm {
 	 * the host computational power. It is used to compensate for the time
 	 * required to encode or decode audio. */
 	unsigned int processing_delay_dms;
+	/* The last reported total codec + processing delay. It is used to limit
+	 * the rate at which changes are reported via D-Bus. */
+	unsigned int reported_codec_delay_dms;
 	/* Positive (or negative) delay reported by the client. */
 	int client_delay_dms;