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tutorial4.c

Tutorial - Part 4: Playing A Tone

Tutorial - Part 4: Playing A Tone

/*
[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;
if (b->requested)
n_frames = SPA_MIN(b->requested, n_frames);
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;
/* sin() gives a value between -1.0 and 1.0, we first apply
* the volume and then scale with 32767.0 to get a 16 bits value
* between [-32767 32767].
* Another common method to convert a double to
* 16 bits is to multiple by 32768.0 and then clamp to
* [-32768 32767] to get the full 16 bits range. */
val = sin(data->accumulator) * DEFAULT_VOLUME * 32767.0;
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] */
format-utils.h
PW_ID_ANY
#define PW_ID_ANY
Definition core.h:77
PW_KEY_MEDIA_TYPE
#define PW_KEY_MEDIA_TYPE
Media.
Definition keys.h:512
PW_KEY_MEDIA_ROLE
#define PW_KEY_MEDIA_ROLE
Role: Movie, Music, Camera, Screen, Communication, Game, Notification, DSP, Production,...
Definition keys.h:518
PW_KEY_MEDIA_CATEGORY
#define PW_KEY_MEDIA_CATEGORY
Media Category: Playback, Capture, Duplex, Monitor, Manager.
Definition keys.h:515
pw_log_warn
#define pw_log_warn(...)
Definition log.h:179
pw_main_loop_destroy
void pw_main_loop_destroy(struct pw_main_loop *loop)
Destroy a loop.
Definition main-loop.c:73
pw_main_loop_run
int pw_main_loop_run(struct pw_main_loop *loop)
Run a main loop.
Definition main-loop.c:122
pw_main_loop_new
struct pw_main_loop * pw_main_loop_new(const struct spa_dict *props)
Create a new main loop.
Definition main-loop.c:63
pw_main_loop_get_loop
struct pw_loop * pw_main_loop_get_loop(struct pw_main_loop *loop)
Get the loop implementation.
Definition main-loop.c:96
pw_init
void pw_init(int *argc, char **argv[])
Initialize PipeWire.
Definition pipewire.c:499
PW_DIRECTION_OUTPUT
#define PW_DIRECTION_OUTPUT
Definition port.h:55
pw_properties_new
struct pw_properties * pw_properties_new(const char *key,...)
Make a new properties object.
Definition properties.c:97
pw_stream_connect
int pw_stream_connect(struct pw_stream *stream, enum pw_direction direction, uint32_t target_id, enum pw_stream_flags flags, const struct spa_pod **params, uint32_t n_params)
Connect a stream for input or output on port_path.
Definition stream.c:1972
pw_stream_dequeue_buffer
struct pw_buffer * pw_stream_dequeue_buffer(struct pw_stream *stream)
Get a buffer that can be filled for playback streams or consumed for capture streams.
Definition stream.c:2543
pw_stream_queue_buffer
int pw_stream_queue_buffer(struct pw_stream *stream, struct pw_buffer *buffer)
Submit a buffer for playback or recycle a buffer for capture.
Definition stream.c:2584
pw_stream_new_simple
struct pw_stream * pw_stream_new_simple(struct pw_loop *loop, const char *name, struct pw_properties *props, const struct pw_stream_events *events, void *data)
Definition stream.c:1661
PW_VERSION_STREAM_EVENTS
#define PW_VERSION_STREAM_EVENTS
Definition stream.h:424
pw_stream_destroy
void pw_stream_destroy(struct pw_stream *stream)
Destroy a stream.
Definition stream.c:1780
PW_STREAM_FLAG_MAP_BUFFERS
@ PW_STREAM_FLAG_MAP_BUFFERS
mmap the buffers except DmaBuf that is not explicitly marked as mappable.
Definition stream.h:476
PW_STREAM_FLAG_AUTOCONNECT
@ PW_STREAM_FLAG_AUTOCONNECT
try to automatically connect this stream
Definition stream.h:471
PW_STREAM_FLAG_RT_PROCESS
@ PW_STREAM_FLAG_RT_PROCESS
call process from the realtime thread.
Definition stream.h:479
SPA_AUDIO_INFO_RAW_INIT
#define SPA_AUDIO_INFO_RAW_INIT(...)
Definition raw.h:304
spa_format_audio_raw_build
SPA_API_AUDIO_RAW_UTILS struct spa_pod * spa_format_audio_raw_build(struct spa_pod_builder *builder, uint32_t id, const struct spa_audio_info_raw *info)
Definition raw-utils.h:111
SPA_PARAM_EnumFormat
@ SPA_PARAM_EnumFormat
available formats as SPA_TYPE_OBJECT_Format
Definition param.h:33
SPA_AUDIO_FORMAT_S16
@ SPA_AUDIO_FORMAT_S16
Definition raw.h:96
SPA_POD_BUILDER_INIT
#define SPA_POD_BUILDER_INIT(buffer, size)
Definition builder.h:72
SPA_MIN
#define SPA_MIN(a, b)
Definition defs.h:165
pipewire.h
pipewire/pipewire.h
pw_buffer
a buffer structure obtained from pw_stream_dequeue_buffer().
Definition stream.h:261
pw_buffer::requested
uint64_t requested
For playback streams, this field contains the suggested amount of data to provide.
Definition stream.h:273
pw_buffer::buffer
struct spa_buffer * buffer
the spa buffer
Definition stream.h:262
pw_main_loop
A main loop object.
pw_stream_events
Events for a stream.
Definition stream.h:422
pw_stream
spa_buffer
A Buffer.
Definition buffer.h:110
spa_buffer::datas
struct spa_data * datas
array of data members
Definition buffer.h:114
spa_chunk::stride
int32_t stride
stride of valid data
Definition buffer.h:65
spa_chunk::size
uint32_t size
size of valid data.
Definition buffer.h:63
spa_chunk::offset
uint32_t offset
offset of valid data.
Definition buffer.h:60
spa_data::chunk
struct spa_chunk * chunk
valid chunk of memory
Definition buffer.h:106
spa_data::data
void * data
optional data pointer
Definition buffer.h:105
spa_data::maxsize
uint32_t maxsize
max size of data
Definition buffer.h:104
spa_pod_builder
Definition builder.h:63
spa_pod
Definition pod.h:57