1 files changed, 112 insertions, 0 deletions
diff --git a/doc/tutorial4.c b/doc/tutorial4.c
new file mode 100644
index 0000000..ff0cb27
--- /dev/null
+++ b/doc/tutorial4.c
@@ -0,0 +1,112 @@
+/*
+  [title]
+  \ref page_tutorial4
+  [title]
+ */
+/* [code] */
+#include <math.h>
+
+#include <spa/param/audio/format-utils.h>
+
+#include <pipewire/pipewire.h>
+
+#define M_PI_M2 ( M_PI + M_PI )
+
+#define DEFAULT_RATE		44100
+#define DEFAULT_CHANNELS	2
+#define DEFAULT_VOLUME		0.7
+
+struct data {
+	struct pw_main_loop *loop;
+	struct pw_stream *stream;
+	double accumulator;
+};
+
+/* [on_process] */
+static void on_process(void *userdata)
+{
+	struct data *data = userdata;
+	struct pw_buffer *b;
+	struct spa_buffer *buf;
+	int i, c, n_frames, stride;
+	int16_t *dst, val;
+
+	if ((b = pw_stream_dequeue_buffer(data->stream)) == NULL) {
+		pw_log_warn("out of buffers: %m");
+		return;
+	}
+
+	buf = b->buffer;
+	if ((dst = buf->datas[0].data) == NULL)
+		return;
+
+	stride = sizeof(int16_t) * DEFAULT_CHANNELS;
+	n_frames = buf->datas[0].maxsize / stride;
+
+        for (i = 0; i < n_frames; i++) {
+                data->accumulator += M_PI_M2 * 440 / DEFAULT_RATE;
+                if (data->accumulator >= M_PI_M2)
+                        data->accumulator -= M_PI_M2;
+
+                val = sin(data->accumulator) * DEFAULT_VOLUME * 16767.f;
+                for (c = 0; c < DEFAULT_CHANNELS; c++)
+                        *dst++ = val;
+        }
+
+	buf->datas[0].chunk->offset = 0;
+	buf->datas[0].chunk->stride = stride;
+	buf->datas[0].chunk->size = n_frames * stride;
+
+	pw_stream_queue_buffer(data->stream, b);
+}
+/* [on_process] */
+
+static const struct pw_stream_events stream_events = {
+	PW_VERSION_STREAM_EVENTS,
+	.process = on_process,
+};
+
+int main(int argc, char *argv[])
+{
+	struct data data = { 0, };
+	const struct spa_pod *params[1];
+	uint8_t buffer[1024];
+	struct spa_pod_builder b = SPA_POD_BUILDER_INIT(buffer, sizeof(buffer));
+
+	pw_init(&argc, &argv);
+
+	data.loop = pw_main_loop_new(NULL);
+
+	data.stream = pw_stream_new_simple(
+			pw_main_loop_get_loop(data.loop),
+			"audio-src",
+			pw_properties_new(
+				PW_KEY_MEDIA_TYPE, "Audio",
+				PW_KEY_MEDIA_CATEGORY, "Playback",
+				PW_KEY_MEDIA_ROLE, "Music",
+				NULL),
+			&stream_events,
+			&data);
+
+	params[0] = spa_format_audio_raw_build(&b, SPA_PARAM_EnumFormat,
+			&SPA_AUDIO_INFO_RAW_INIT(
+				.format = SPA_AUDIO_FORMAT_S16,
+				.channels = DEFAULT_CHANNELS,
+				.rate = DEFAULT_RATE ));
+
+	pw_stream_connect(data.stream,
+			  PW_DIRECTION_OUTPUT,
+			  PW_ID_ANY,
+			  PW_STREAM_FLAG_AUTOCONNECT |
+			  PW_STREAM_FLAG_MAP_BUFFERS |
+			  PW_STREAM_FLAG_RT_PROCESS,
+			  params, 1);
+
+	pw_main_loop_run(data.loop);
+
+	pw_stream_destroy(data.stream);
+	pw_main_loop_destroy(data.loop);
+
+	return 0;
+}
+/* [code] */