examples: add audio capture example

src/examples/audio-capture.c

@@ -0,0 +1,200 @@
+/* PipeWire
+ *
+ * Copyright © 2022 Wim Taymans
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+/*
+ [title]
+ Audio capture using \ref pw_stream "pw_stream".
+ [title]
+ */
+
+#include <stdio.h>
+#include <errno.h>
+#include <math.h>
+#include <signal.h>
+
+#include <spa/param/audio/format-utils.h>
+
+#include <pipewire/pipewire.h>
+
+struct data {
+	struct pw_main_loop *loop;
+	struct pw_stream *stream;
+
+	struct spa_audio_info format;
+};
+
+/* our data processing function is in general:
+ *
+ *  struct pw_buffer *b;
+ *  b = pw_stream_dequeue_buffer(stream);
+ *
+ *  .. consume stuff in the buffer ...
+ *
+ *  pw_stream_queue_buffer(stream, b);
+ */
+static void on_process(void *userdata)
+{
+	struct data *data = userdata;
+	struct pw_buffer *b;
+	struct spa_buffer *buf;
+	float *samples, max;
+	uint32_t c, n, n_channels, n_samples;
+
+	if ((b = pw_stream_dequeue_buffer(data->stream)) == NULL) {
+		pw_log_warn("out of buffers: %m");
+		return;
+	}
+
+	buf = b->buffer;
+	if ((samples = buf->datas[0].data) == NULL)
+		return;
+
+	n_channels = data->format.info.raw.channels;
+	n_samples = buf->datas[0].chunk->size / sizeof(float);
+
+	fprintf(stdout, "captured %d samples\n", n_samples / n_channels);
+	for (c = 0; c < data->format.info.raw.channels; c++) {
+		max = 0.0f;
+		for (n = c; n < n_samples; n += n_channels)
+			max = fmaxf(max, fabsf(samples[n]));
+
+		fprintf(stdout, "channel %d: peak:%f %*s %*s\n",
+				c, max, (int)(max * 30.0f), "*", 30, "");
+	}
+	/* move cursor up */
+	fprintf(stdout, "%c[%dA", 0x1b, n_channels + 1);
+	fflush(stdout);
+
+	pw_stream_queue_buffer(data->stream, b);
+}
+
+/* Be notified when the stream param changes. We're only looking at the
+ * format changes.
+ */
+static void
+on_stream_param_changed(void *_data, uint32_t id, const struct spa_pod *param)
+{
+	struct data *data = _data;
+
+	/* NULL means to clear the format */
+	if (param == NULL || id != SPA_PARAM_Format)
+		return;
+
+	if (spa_format_parse(param, &data->format.media_type, &data->format.media_subtype) < 0)
+		return;
+
+	/* only accept raw audio */
+	if (data->format.media_type != SPA_MEDIA_TYPE_audio ||
+	    data->format.media_subtype != SPA_MEDIA_SUBTYPE_raw)
+		return;
+
+	/* call a helper function to parse the format for us. */
+	spa_format_audio_raw_parse(param, &data->format.info.raw);
+
+	fprintf(stdout, "capturing rate:%d channels:%d\n",
+			data->format.info.raw.rate, data->format.info.raw.channels);
+
+}
+
+static const struct pw_stream_events stream_events = {
+	PW_VERSION_STREAM_EVENTS,
+	.param_changed = on_stream_param_changed,
+	.process = on_process,
+};
+
+static void do_quit(void *userdata, int signal_number)
+{
+	struct data *data = userdata;
+	pw_main_loop_quit(data->loop);
+}
+
+int main(int argc, char *argv[])
+{
+	struct data data = { 0, };
+	const struct spa_pod *params[1];
+	uint8_t buffer[1024];
+	struct pw_properties *props;
+	struct spa_pod_builder b = SPA_POD_BUILDER_INIT(buffer, sizeof(buffer));
+
+	pw_init(&argc, &argv);
+
+	/* make a main loop. If you already have another main loop, you can add
+	 * the fd of this pipewire mainloop to it. */
+	data.loop = pw_main_loop_new(NULL);
+
+	pw_loop_add_signal(pw_main_loop_get_loop(data.loop), SIGINT, do_quit, &data);
+	pw_loop_add_signal(pw_main_loop_get_loop(data.loop), SIGTERM, do_quit, &data);
+
+	/* Create a simple stream, the simple stream manages the core and remote
+	 * objects for you if you don't need to deal with them.
+	 *
+	 * If you plan to autoconnect your stream, you need to provide at least
+	 * media, category and role properties.
+	 *
+	 * Pass your events and a user_data pointer as the last arguments. This
+	 * will inform you about the stream state. The most important event
+	 * you need to listen to is the process event where you need to produce
+	 * the data.
+	 */
+	props = pw_properties_new(PW_KEY_MEDIA_TYPE, "Audio",
+			PW_KEY_MEDIA_CATEGORY, "Capture",
+			PW_KEY_MEDIA_ROLE, "Music",
+			NULL);
+	if (argc > 1)
+		/* Set stream target if given on command line */
+		pw_properties_set(props, PW_KEY_TARGET_OBJECT, argv[1]);
+	data.stream = pw_stream_new_simple(
+			pw_main_loop_get_loop(data.loop),
+			"audio-capture",
+			props,
+			&stream_events,
+			&data);
+
+	/* Make one parameter with the supported formats. The SPA_PARAM_EnumFormat
+	 * id means that this is a format enumeration (of 1 value).
+	 * We leave the channels and rate empty to accept the native graph
+	 * rate and channels. */
+	params[0] = spa_format_audio_raw_build(&b, SPA_PARAM_EnumFormat,
+			&SPA_AUDIO_INFO_RAW_INIT(
+				.format = SPA_AUDIO_FORMAT_F32));
+
+	/* Now connect this stream. We ask that our process function is
+	 * called in a realtime thread. */
+	pw_stream_connect(data.stream,
+			  PW_DIRECTION_INPUT,
+			  PW_ID_ANY,
+			  PW_STREAM_FLAG_AUTOCONNECT |
+			  PW_STREAM_FLAG_MAP_BUFFERS |
+			  PW_STREAM_FLAG_RT_PROCESS,
+			  params, 1);
+
+	/* and wait while we let things run */
+	pw_main_loop_run(data.loop);
+
+	pw_stream_destroy(data.stream);
+	pw_main_loop_destroy(data.loop);
+	pw_deinit();
+
+	return 0;
+}

src/examples/meson.build

@@ -3,6 +3,7 @@ examples = [
   'audio-src',
   'audio-dsp-src',
   'audio-dsp-filter',
+  'audio-capture',
   'video-play',
   'video-src',
   'video-dsp-play',