bluez5: add PLC for MSBC using spandsp

Use spandsp as optional dependency for MSBC codec, for providing PLC.

meson_options.txt

@@ -153,6 +153,10 @@ option('bluez5-codec-g722',
         description: 'Enable G722 open source codec implementation',
         type: 'feature',
         value: 'auto')
+option('bluez5-plc-spandsp',
+        description: 'Enable SpanDSP for packet loss concealment',
+        type: 'feature',
+        value: 'auto')
 option('control',
        description: 'Enable control spa plugin integration',
        type: 'feature',

spa/meson.build

@@ -111,6 +111,9 @@ if get_option('spa-plugins').allowed()
     endif
     g722_codec_option = get_option('bluez5-codec-g722')
     summary({'G722': g722_codec_option.allowed()}, bool_yn: true, section: 'Bluetooth audio codecs')
+
+    spandsp_dep = dependency('spandsp', required : get_option('bluez5-plc-spandsp'))
+    cdata.set('HAVE_SPANDSP', spandsp_dep.found())
   endif
 
   have_vulkan = false

spa/plugins/bluez5/hfp-codec-msbc.c

@@ -3,6 +3,8 @@
 /* SPDX-FileCopyrightText: Copyright © 2025 Pauli Virtanen */
 /* SPDX-License-Identifier: MIT */
 
+#include "config.h"
+
 #include <unistd.h>
 #include <string.h>
 #include <stddef.h>
@@ -24,10 +26,12 @@
 
 #include "media-codecs.h"
 #include "hfp-h2.h"
+#include "plc.h"
+
 
 #define MSBC_BLOCK_SIZE		240
 
-static struct spa_log *log;
+static struct spa_log *log_;
 
 struct impl {
 	sbc_t msbc;
@@ -36,6 +40,8 @@ struct impl {
 
 	void *data;
 	size_t avail;
+
+	plc_state_t *plc;
 };
 
 static int codec_enum_config(const struct media_codec *codec, uint32_t flags,
@@ -104,6 +110,10 @@ static void *codec_init(const struct media_codec *codec, uint32_t flags,
 
 	h2_reader_init(&this->h2, true);
 
+	this->plc = plc_init(NULL);
+	if (!this->plc)
+		return NULL;
+
 	return spa_steal_ptr(this);
 }
 
@@ -112,6 +122,7 @@ static void codec_deinit(void *data)
 	struct impl *this = data;
 
 	sbc_finish(&this->msbc);
+	plc_free(this->plc);
 	free(this);
 }
 
@@ -198,13 +209,30 @@ static int codec_decode(void *data,
 		return consumed;
 	}
 
+	plc_rx(this->plc, dst, *dst_out / sizeof(int16_t));
+
 	return consumed;
 }
 
+static int codec_produce_plc(void *data, void *dst, size_t dst_size)
+{
+	struct impl *this = data;
+	int res;
+
+	if (dst_size < MSBC_BLOCK_SIZE)
+		return -EINVAL;
+
+	res = plc_fillin(this->plc, dst, MSBC_BLOCK_SIZE / sizeof(int16_t));
+	if (res < 0)
+		return res;
+
+	return MSBC_BLOCK_SIZE;
+}
+
 static void codec_set_log(struct spa_log *global_log)
 {
-	log = global_log;
+	log_ = global_log;
-	spa_log_topic_init(log, &codec_plugin_log_topic);
+	spa_log_topic_init(log_, &codec_plugin_log_topic);
 }
 
 const struct media_codec hfp_codec_msbc = {
@@ -221,6 +249,7 @@ const struct media_codec hfp_codec_msbc = {
 	.set_log = codec_set_log,
 	.start_decode = codec_start_decode,
 	.decode = codec_decode,
+	.produce_plc = codec_produce_plc,
 	.name = "msbc",
 	.description = "MSBC",
 	.stream_pkt = true,

spa/plugins/bluez5/meson.build

@@ -110,7 +110,7 @@ bluez_codec_hfp_msbc = shared_library('spa-codec-bluez5-hfp-msbc',
   [ 'hfp-codec-msbc.c', 'media-codecs.c' ],
   include_directories : [ configinc ],
   c_args : codec_args,
-  dependencies : [ spa_dep, sbc_dep ],
+  dependencies : [ spa_dep, sbc_dep, spandsp_dep ],
   install : true,
   install_dir : spa_plugindir / 'bluez5')
 

spa/plugins/bluez5/plc.h

@@ -0,0 +1,26 @@
+/* Spa PLC */
+/* SPDX-FileCopyrightText: Copyright © 2025 Pauli Virtanen */
+/* SPDX-License-Identifier: MIT */
+
+#ifndef SPA_BLUEZ5_PLC_H
+#define SPA_BLUEZ5_PLC_H
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#ifdef HAVE_SPANDSP
+#include <spandsp.h>
+#else
+typedef struct { char dummy; } plc_state_t;
+static inline int plc_rx(plc_state_t *s, int16_t *data, int len) { return -ENOTSUP; }
+static inline int plc_fillin(plc_state_t *s, int16_t *data, int len) { return -ENOTSUP; }
+static inline plc_state_t *plc_init(plc_state_t *s)
+{
+	static plc_state_t state;
+	return &state;
+}
+static inline int plc_free(plc_state_t *s) { return 0; }
+#endif
+
+#endif