From 48a0cd1377d2216f79468322c2b7c956d216674c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9l=C3=A8ne=20Corbineau?= <selene.corbineau@ens.fr>
Date: Thu, 16 Jan 2025 23:35:35 +0100
Subject: [PATCH] Basic whitenoise generator

---
 pw_plugin/Makefile |  2 +-
 pw_plugin/main.c   | 12 ------
 pw_plugin/main.cc  | 92 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 93 insertions(+), 13 deletions(-)
 delete mode 100644 pw_plugin/main.c
 create mode 100644 pw_plugin/main.cc

diff --git a/pw_plugin/Makefile b/pw_plugin/Makefile
index 9e010c2..3207131 100644
--- a/pw_plugin/Makefile
+++ b/pw_plugin/Makefile
@@ -2,4 +2,4 @@
 
 build: main.out
 main.out: main.o
-	$(CC) $(LDFLAGS) $^ -o $@
+	$(CXX) $(LDFLAGS) $^ -o $@
diff --git a/pw_plugin/main.c b/pw_plugin/main.c
deleted file mode 100644
index 60f5de2..0000000
--- a/pw_plugin/main.c
+++ /dev/null
@@ -1,12 +0,0 @@
-#include <pipewire/pipewire.h>
- 
-int main(int argc, char *argv[])
-{
-        pw_init(&argc, &argv);
- 
-        fprintf(stdout, "Compiled with libpipewire %s\n"
-                        "Linked with libpipewire %s\n",
-                                pw_get_headers_version(),
-                                pw_get_library_version());
-        return 0;
-}
diff --git a/pw_plugin/main.cc b/pw_plugin/main.cc
new file mode 100644
index 0000000..dbf2369
--- /dev/null
+++ b/pw_plugin/main.cc
@@ -0,0 +1,92 @@
+#include <random>
+#include <cstdio>
+#include "pipewire/pipewire.h"
+#include "spa/param/audio/format-utils.h"
+
+struct local_data {
+	pw_main_loop* loop;
+	pw_stream* stream;
+
+	std::mt19937 gen;
+	std::normal_distribution<float> nd{0, 0.3};
+};
+
+void on_process(local_data* ld) {
+	pw_buffer *b;
+	spa_buffer *buf;
+	if((b = pw_stream_dequeue_buffer(ld->stream)) == NULL) {
+		pw_log_warn("No buffers left!");
+		return;
+	}
+
+	buf = b->buffer;
+
+	float* dst;
+	if((dst = (float*)buf->datas[0].data) == NULL) {
+		return;
+	}
+
+	int n_frames = buf->datas[0].maxsize / sizeof(float);
+	if(b->requested) {
+		n_frames = SPA_MIN(b->requested, n_frames);
+	}
+
+	for(int i = 0; i < n_frames; ++i) {
+		*dst++ = ld->nd(ld->gen);
+	}
+
+	buf->datas[0].chunk->offset = 0;
+	buf->datas[0].chunk->stride = sizeof(float);
+	buf->datas[0].chunk->size = n_frames * sizeof(float);
+
+	pw_stream_queue_buffer(ld->stream, b);
+}
+
+const struct pw_stream_events stream_events {
+	PW_VERSION_STREAM_EVENTS,
+	.process = (void(*)(void*))on_process,
+};
+
+int main(int argc, char** argv) {
+	// We do NOT seed the MT engine -> the time series will be predictable!
+	local_data bookkeep{nullptr,nullptr,};
+
+	pw_init(&argc, &argv);
+	bookkeep.loop = pw_main_loop_new(NULL);
+
+	bookkeep.stream = pw_stream_new_simple(
+		pw_main_loop_get_loop(bookkeep.loop),
+		"audio-src",
+		pw_properties_new(
+			PW_KEY_MEDIA_TYPE, "Audio",
+			PW_KEY_MEDIA_CATEGORY, "Playback",
+			PW_KEY_MEDIA_ROLE, "Test",
+			NULL),
+		&stream_events,
+		&bookkeep);
+
+	const spa_pod* params[1];
+	uint8_t buffer[1024];
+	spa_pod_builder b = SPA_POD_BUILDER_INIT(buffer, sizeof(buffer));
+
+	auto audio_info = SPA_AUDIO_INFO_RAW_INIT(
+			.format = SPA_AUDIO_FORMAT_F32_LE,
+			.rate = 44100,
+			.channels = 1,);
+
+	params[0] = spa_format_audio_raw_build(&b, SPA_PARAM_EnumFormat,&audio_info);
+
+	pw_stream_connect(bookkeep.stream,
+		PW_DIRECTION_OUTPUT,
+		PW_ID_ANY,
+		(pw_stream_flags)(PW_STREAM_FLAG_AUTOCONNECT |
+		PW_STREAM_FLAG_MAP_BUFFERS |
+		PW_STREAM_FLAG_RT_PROCESS),
+		params, 1);
+
+	pw_main_loop_run(bookkeep.loop);
+
+	pw_stream_destroy(bookkeep.stream);
+	pw_main_loop_destroy(bookkeep.loop);
+	return 0;
+}