From 0003d7a2d03e75c5a7400a170ba5cb3c27bcf6c5 Mon Sep 17 00:00:00 2001
From: Pauli Virtanen <pav@iki.fi>
Date: Tue, 6 Jan 2026 16:11:37 +0200
Subject: [PATCH] bluez5: iso-io: add debug option for forcing same data in all
 streams

When debugging desync issues, it's useful to force same data be sent on
all ISO streams. Add option for that.
---
 doc/dox/config/pipewire-props.7.md |  4 ++++
 spa/plugins/bluez5/iso-io.c        | 27 +++++++++++++++++++++++++++
 spa/plugins/bluez5/iso-io.h        |  2 ++
 spa/plugins/bluez5/media-sink.c    |  6 ++++++
 4 files changed, 39 insertions(+)

diff --git a/doc/dox/config/pipewire-props.7.md b/doc/dox/config/pipewire-props.7.md
index dd5df08ea..c16839b59 100644
--- a/doc/dox/config/pipewire-props.7.md
+++ b/doc/dox/config/pipewire-props.7.md
@@ -1382,6 +1382,10 @@ Latency adjustment to apply on the node. Larger values add a
 constant latency, but reduces timing jitter caused by Bluetooth
 transport.
 
+@PAR@ node-prop bluez5.debug.iso-mono = false  # boolean
+Debugging option for forcing ISO sinks send identical packets out for
+all streams.
+
 # PORT PROPERTIES  @IDX@ props
 
 Port properties are usually not directly configurable via PipeWire
diff --git a/spa/plugins/bluez5/iso-io.c b/spa/plugins/bluez5/iso-io.c
index 85c211492..f53da2f4d 100644
--- a/spa/plugins/bluez5/iso-io.c
+++ b/spa/plugins/bluez5/iso-io.c
@@ -257,6 +257,7 @@ static void group_on_timeout(struct spa_source *source)
 	struct stream *stream;
 	bool resync = false;
 	bool fail = false;
+	bool debug_mono = false;
 	uint64_t exp;
 	uint64_t now_realtime;
 	int res;
@@ -295,6 +296,8 @@ static void group_on_timeout(struct spa_source *source)
 
 		if (!group->started && !stream->idle && stream->this.size > 0)
 			group->started = true;
+
+		debug_mono = debug_mono || stream->this.debug_mono;
 	}
 
 	if (group_latency_check(group)) {
@@ -303,6 +306,30 @@ static void group_on_timeout(struct spa_source *source)
 		goto done;
 	}
 
+	/* Force same data in all streams */
+	if (debug_mono) {
+		struct stream *s0 = NULL;
+
+		spa_list_for_each(stream, &group->streams, link) {
+			if (!stream->sink)
+				continue;
+			if (stream->this.size) {
+				s0 = stream;
+				break;
+			}
+		}
+		if (s0) {
+			spa_list_for_each(stream, &group->streams, link) {
+				if (!stream->sink)
+					continue;
+				if (stream != s0) {
+					stream->this.size = s0->this.size;
+					memcpy(stream->this.buf, s0->this.buf, s0->this.size);
+				}
+			}
+		}
+	}
+
 	/* Produce output */
 	spa_list_for_each(stream, &group->streams, link) {
 		int res = 0;
diff --git a/spa/plugins/bluez5/iso-io.h b/spa/plugins/bluez5/iso-io.h
index a0082b420..eb3a94415 100644
--- a/spa/plugins/bluez5/iso-io.h
+++ b/spa/plugins/bluez5/iso-io.h
@@ -35,6 +35,8 @@ struct spa_bt_iso_io
 	struct spa_audio_info format;	/**< Audio format */
 	void *codec_data;		/**< Codec data */
 
+	bool debug_mono;	/**< Duplicate packets from first sink to other sinks */
+
 	void *user_data;
 };
 
diff --git a/spa/plugins/bluez5/media-sink.c b/spa/plugins/bluez5/media-sink.c
index 136ac6d82..290852f16 100644
--- a/spa/plugins/bluez5/media-sink.c
+++ b/spa/plugins/bluez5/media-sink.c
@@ -159,6 +159,7 @@ struct impl {
 
 	unsigned int is_duplex:1;
 	unsigned int is_internal:1;
+	unsigned int iso_debug_mono:1;
 
 	struct spa_source source;
 	int timerfd;
@@ -1566,6 +1567,8 @@ static int transport_start(struct impl *this)
 					this->codec->description);
 			return -EIO;
 		}
+
+		this->transport->iso_io->debug_mono = this->iso_debug_mono;
 	} else {
 		this->own_codec_data = false;
 		this->codec_data = this->transport->iso_io->codec_data;
@@ -2625,6 +2628,9 @@ impl_init(const struct spa_handle_factory *factory,
 	if (info && (str = spa_dict_lookup(info, "api.bluez5.internal")) != NULL)
 		this->is_internal = spa_atob(str);
 
+	if (info && (str = spa_dict_lookup(info, "bluez5.debug.iso-mono")) != NULL)
+		this->iso_debug_mono = spa_atob(str);
+
 	if (info && (str = spa_dict_lookup(info, SPA_KEY_API_BLUEZ5_TRANSPORT)))
 		sscanf(str, "pointer:%p", &this->transport);