PipeWire 1.0.7
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Exporting and implementing a video source SPA node, using Core API.

/* PipeWire */
/* SPDX-FileCopyrightText: Copyright © 2018 Wim Taymans */
/* SPDX-License-Identifier: MIT */
Exporting and implementing a video source SPA node, using \ref api_pw_core.
#include <errno.h>
#include <stdio.h>
#include <math.h>
#include <sys/mman.h>
#include <spa/node/io.h>
#include <spa/node/utils.h>
#include <spa/pod/filter.h>
#define M_PI_M2 ( M_PI + M_PI )
#define BUFFER_SAMPLES 128
#define MAX_BUFFERS 32
struct buffer {
uint32_t id;
struct spa_buffer *buffer;
struct spa_list link;
void *ptr;
bool mapped;
struct data {
const char *path;
struct pw_main_loop *loop;
struct pw_context *context;
struct pw_core *core;
struct spa_hook core_listener;
uint64_t info_all;
struct spa_port_info info;
struct spa_dict_item items[1];
struct spa_dict dict;
struct spa_param_info params[5];
struct spa_node impl_node;
struct spa_hook_list hooks;
struct spa_io_buffers *io;
struct spa_io_control *io_notify;
uint32_t io_notify_size;
struct spa_audio_info_raw format;
struct buffer buffers[MAX_BUFFERS];
uint32_t n_buffers;
struct spa_list empty;
double accumulator;
double volume_accum;
static void update_volume(struct data *data)
struct spa_pod_builder b = { 0, };
struct spa_pod_frame f[2];
if (data->io_notify == NULL)
spa_pod_builder_init(&b, data->io_notify, data->io_notify_size);
spa_pod_builder_float(&b, (sin(data->volume_accum) / 2.0) + 0.5);
spa_pod_builder_pop(&b, &f[1]);
spa_pod_builder_pop(&b, &f[0]);
data->volume_accum += M_PI_M2 / 1000.0;
if (data->volume_accum >= M_PI_M2)
data->volume_accum -= M_PI_M2;
static int impl_send_command(void *object, const struct spa_command *command)
return 0;
static int impl_add_listener(void *object,
struct spa_hook *listener,
const struct spa_node_events *events,
void *data)
struct data *d = object;
struct spa_hook_list save;
uint64_t old;
spa_hook_list_isolate(&d->hooks, &save, listener, events, data);
old = d->info.change_mask;
d->info.change_mask = d->info_all;
d->info.change_mask = old;
spa_hook_list_join(&d->hooks, &save);
return 0;
static int impl_set_callbacks(void *object,
const struct spa_node_callbacks *callbacks, void *data)
return 0;
static int impl_set_io(void *object,
uint32_t id, void *data, size_t size)
return 0;
static int impl_port_set_io(void *object, enum spa_direction direction, uint32_t port_id,
uint32_t id, void *data, size_t size)
struct data *d = object;
switch (id) {
d->io = data;
d->io_notify = data;
d->io_notify_size = size;
return -ENOENT;
return 0;
static int impl_port_enum_params(void *object, int seq,
enum spa_direction direction, uint32_t port_id,
uint32_t id, uint32_t start, uint32_t num,
const struct spa_pod *filter)
struct data *d = object;
struct spa_pod *param;
struct spa_pod_builder b = { 0 };
uint8_t buffer[1024];
struct spa_result_node_params result;
uint32_t count = 0;
result.id = id;
result.next = start;
result.index = result.next++;
spa_pod_builder_init(&b, buffer, sizeof(buffer));
switch (id) {
if (result.index != 0)
return 0;
if (result.index != 0)
return 0;
if (d->format.format == 0)
return 0;
param = spa_format_audio_raw_build(&b, id, &d->format);
if (result.index > 0)
return 0;
BUFFER_SAMPLES * sizeof(float), 32, INT32_MAX),
switch (result.index) {
case 0:
return 0;
switch (result.index) {
case 0:
case 1:
SPA_PARAM_IO_size, SPA_POD_Int(sizeof(struct spa_io_sequence) + 1024));
return 0;
return -ENOENT;
if (spa_pod_filter(&b, &result.param, param, filter) < 0)
goto next;
spa_node_emit_result(&d->hooks, seq, 0, SPA_RESULT_TYPE_NODE_PARAMS, &result);
if (++count != num)
goto next;
return 0;
static int port_set_format(void *object,
enum spa_direction direction, uint32_t port_id,
uint32_t flags, const struct spa_pod *format)
struct data *d = object;
if (format == NULL) {
} else {
spa_debug_format(0, NULL, format);
if (spa_format_audio_raw_parse(format, &d->format) < 0)
return -EINVAL;
if (d->format.format != SPA_AUDIO_FORMAT_S16 &&
d->format.format != SPA_AUDIO_FORMAT_F32)
return -EINVAL;
if (d->format.rate == 0 ||
d->format.channels == 0 ||
d->format.channels > SPA_AUDIO_MAX_CHANNELS)
return -EINVAL;
d->info.change_mask = SPA_PORT_CHANGE_MASK_PARAMS;
if (format) {
} else {
d->params[4] = SPA_PARAM_INFO(SPA_PARAM_Buffers, 0);
return 0;
static int impl_port_set_param(void *object,
enum spa_direction direction, uint32_t port_id,
uint32_t id, uint32_t flags,
const struct spa_pod *param)
if (id == SPA_PARAM_Format) {
return port_set_format(object, direction, port_id, flags, param);
return -ENOENT;
static int impl_port_use_buffers(void *object,
enum spa_direction direction, uint32_t port_id,
uint32_t flags,
struct spa_buffer **buffers, uint32_t n_buffers)
struct data *d = object;
uint32_t i;
if (n_buffers > MAX_BUFFERS)
return -ENOSPC;
for (i = 0; i < n_buffers; i++) {
struct buffer *b = &d->buffers[i];
struct spa_data *datas = buffers[i]->datas;
if (datas[0].data != NULL) {
b->ptr = datas[0].data;
b->mapped = false;
else if (datas[0].type == SPA_DATA_MemFd ||
datas[0].type == SPA_DATA_DmaBuf) {
b->ptr = mmap(NULL, datas[0].maxsize + datas[0].mapoffset, PROT_WRITE,
MAP_SHARED, datas[0].fd, 0);
if (b->ptr == MAP_FAILED) {
pw_log_error("failed to buffer mem");
return -errno;
b->ptr = SPA_PTROFF(b->ptr, datas[0].mapoffset, void);
b->mapped = true;
else {
pw_log_error("invalid buffer mem");
return -EINVAL;
b->id = i;
b->buffer = buffers[i];
pw_log_debug("got buffer %d size %d", i, datas[0].maxsize);
spa_list_append(&d->empty, &b->link);
d->n_buffers = n_buffers;
return 0;
static inline void reuse_buffer(struct data *d, uint32_t id)
pw_log_trace("export-source %p: recycle buffer %d", d, id);
spa_list_append(&d->empty, &d->buffers[id].link);
static int impl_port_reuse_buffer(void *object, uint32_t port_id, uint32_t buffer_id)
struct data *d = object;
reuse_buffer(d, buffer_id);
return 0;
static void fill_f32(struct data *d, void *dest, int avail)
float *dst = dest;
int n_samples = avail / (sizeof(float) * d->format.channels);
int i;
uint32_t c;
for (i = 0; i < n_samples; i++) {
float val;
d->accumulator += M_PI_M2 * 440 / d->format.rate;
if (d->accumulator >= M_PI_M2)
d->accumulator -= M_PI_M2;
val = sin(d->accumulator);
for (c = 0; c < d->format.channels; c++)
*dst++ = val;
static void fill_s16(struct data *d, void *dest, int avail)
int16_t *dst = dest;
int n_samples = avail / (sizeof(int16_t) * d->format.channels);
int i;
uint32_t c;
for (i = 0; i < n_samples; i++) {
int16_t val;
d->accumulator += M_PI_M2 * 440 / d->format.rate;
if (d->accumulator >= M_PI_M2)
d->accumulator -= M_PI_M2;
val = (int16_t) (sin(d->accumulator) * 32767.0);
for (c = 0; c < d->format.channels; c++)
*dst++ = val;
static int impl_node_process(void *object)
struct data *d = object;
struct buffer *b;
int avail;
struct spa_io_buffers *io = d->io;
uint32_t maxsize, index = 0;
uint32_t filled, offset;
struct spa_data *od;
if (io->buffer_id < d->n_buffers) {
reuse_buffer(d, io->buffer_id);
if (spa_list_is_empty(&d->empty)) {
pw_log_error("export-source %p: out of buffers", d);
return -EPIPE;
b = spa_list_first(&d->empty, struct buffer, link);
od = b->buffer->datas;
maxsize = od[0].maxsize;
filled = 0;
index = 0;
avail = maxsize - filled;
offset = index % maxsize;
if (offset + avail > maxsize)
avail = maxsize - offset;
if (d->format.format == SPA_AUDIO_FORMAT_S16)
fill_s16(d, SPA_PTROFF(b->ptr, offset, void), avail);
else if (d->format.format == SPA_AUDIO_FORMAT_F32)
fill_f32(d, SPA_PTROFF(b->ptr, offset, void), avail);
od[0].chunk->offset = 0;
od[0].chunk->size = avail;
od[0].chunk->stride = 0;
io->buffer_id = b->id;
static const struct spa_node_methods impl_node = {
.add_listener = impl_add_listener,
.set_callbacks = impl_set_callbacks,
.set_io = impl_set_io,
.send_command = impl_send_command,
.port_set_io = impl_port_set_io,
.port_enum_params = impl_port_enum_params,
.port_set_param = impl_port_set_param,
.port_use_buffers = impl_port_use_buffers,
.port_reuse_buffer = impl_port_reuse_buffer,
.process = impl_node_process,
static void make_node(struct data *data)
struct pw_properties *props;
if (data->path)
data->impl_node.iface = SPA_INTERFACE_INIT(
&impl_node, data);
&props->dict, &data->impl_node, 0);
static void on_core_error(void *data, uint32_t id, int seq, int res, const char *message)
struct data *d = data;
pw_log_error("error id:%u seq:%d res:%d (%s): %s",
id, seq, res, spa_strerror(res), message);
if (id == PW_ID_CORE)
static const struct pw_core_events core_events = {
.error = on_core_error,
int main(int argc, char *argv[])
struct data data = { 0, };
pw_init(&argc, &argv);
data.loop = pw_main_loop_new(NULL);
data.context = pw_context_new(pw_main_loop_get_loop(data.loop), NULL, 0);
data.path = argc > 1 ? argv[1] : NULL;
data.info_all = SPA_PORT_CHANGE_MASK_FLAGS |
data.info = SPA_PORT_INFO_INIT();
data.info.flags = 0;
data.items[0] = SPA_DICT_ITEM_INIT(PW_KEY_FORMAT_DSP, "32 bit float mono audio");
data.dict = SPA_DICT_INIT_ARRAY(data.items);
data.info.props = &data.dict;
data.params[4] = SPA_PARAM_INFO(SPA_PARAM_Buffers, 0);
data.info.params = data.params;
data.info.n_params = 5;
if ((data.core = pw_context_connect(data.context, NULL, 0)) == NULL) {
printf("can't connect: %m\n");
return -1;
pw_core_add_listener(data.core, &data.core_listener, &core_events, &data);
return 0;
void pw_context_destroy(struct pw_context *context)
destroy a context object, all resources except the main_loop will be destroyed
Definition context.c:393
struct pw_context * pw_context_new(struct pw_loop *main_loop, struct pw_properties *props, size_t user_data_size)
Make a new context object for a given main_loop.
Definition context.c:179
#define PW_ID_CORE
default ID for the core object after connect
Definition core.h:62
struct pw_core * pw_context_connect(struct pw_context *context, struct pw_properties *properties, size_t user_data_size)
Connect to a PipeWire instance.
Definition core.c:394
struct pw_proxy * pw_core_export(struct pw_core *core, const char *type, const struct spa_dict *props, void *object, size_t user_data_size)
Export an object into the PipeWire instance associated with core.
Definition core.c:269
#define pw_core_add_listener(c,...)
Definition core.h:364
Definition core.h:128
Definition keys.h:438
node wants to be automatically connected to a compatible node
Definition keys.h:207
a target object to link to.
Definition keys.h:505
Role: Movie, Music, Camera, Screen, Communication, Game, Notification, DSP, Production,...
Definition keys.h:444
node wants exclusive access to resources
Definition keys.h:205
Media Category: Playback, Capture, Duplex, Monitor, Manager.
Definition keys.h:441
format related properties
Definition keys.h:481
#define pw_log_trace(...)
Definition log.h:135
#define pw_log_debug(...)
Definition log.h:134
#define pw_log_error(...)
Definition log.h:131
int pw_main_loop_quit(struct pw_main_loop *loop)
Quit a main loop.
Definition main-loop.c:106
void pw_main_loop_destroy(struct pw_main_loop *loop)
Destroy a loop.
Definition main-loop.c:71
int pw_main_loop_run(struct pw_main_loop *loop)
Run a main loop.
Definition main-loop.c:120
struct pw_main_loop * pw_main_loop_new(const struct spa_dict *props)
Create a new main loop.
Definition main-loop.c:61
struct pw_loop * pw_main_loop_get_loop(struct pw_main_loop *loop)
Get the loop implementation.
Definition main-loop.c:94
void pw_init(int *argc, char **argv[])
Initialize PipeWire.
Definition pipewire.c:556
void pw_properties_free(struct pw_properties *properties)
Free a properties object.
Definition properties.c:351
struct pw_properties * pw_properties_new(const char *key,...)
Make a new properties object.
Definition properties.c:85
int pw_properties_set(struct pw_properties *properties, const char *key, const char *value)
Set a property value.
Definition properties.c:422
@ SPA_META_Header
struct spa_meta_header
Definition meta.h:27
generic fd, mmap to get to memory
Definition buffer.h:35
fd to dmabuf memory
Definition buffer.h:36
@ SPA_CONTROL_Properties
data contains a SPA_TYPE_OBJECT_Props
Definition control.h:32
static int spa_debug_format(int indent, const struct spa_type_info *info, const struct spa_pod *format)
Definition format.h:206
#define SPA_DICT_ITEM_INIT(key, value)
Definition dict.h:37
#define SPA_DICT_INIT_ARRAY(items)
Definition dict.h:50
static void spa_hook_list_join(struct spa_hook_list *list, struct spa_hook_list *save)
Definition hook.h:422
static void spa_hook_list_init(struct spa_hook_list *list)
Initialize a hook list to the empty list.
Definition hook.h:360
static void spa_hook_list_isolate(struct spa_hook_list *list, struct spa_hook_list *save, struct spa_hook *hook, const void *funcs, void *data)
Definition hook.h:408
#define SPA_INTERFACE_INIT(_type, _version, _funcs, _data)
Initialize a spa_interface.
Definition hook.h:157
static void spa_list_init(struct spa_list *list)
Definition list.h:35
static void spa_list_remove(struct spa_list *elem)
Definition list.h:65
#define spa_list_first(head, type, member)
Definition list.h:71
#define spa_list_is_empty(l)
Definition list.h:45
#define spa_list_append(list, item)
Definition list.h:77
Definition node.h:95
Definition node.h:99
#define spa_node_emit_port_info(hooks,...)
Definition utils.h:118
Definition node.h:139
Definition io.h:84
Definition node.h:37
Definition node.h:40
Definition node.h:101
Definition node.h:144
#define spa_node_emit_result(hooks,...)
Definition utils.h:119
Definition node.h:331
@ SPA_IO_Notify
area for notify messages, struct spa_io_sequence
Definition io.h:43
@ SPA_IO_Buffers
area to exchange buffers, struct spa_io_buffers
Definition io.h:38
Definition param.h:59
static struct spa_pod * spa_format_audio_raw_build(struct spa_pod_builder *builder, uint32_t id, struct spa_audio_info_raw *info)
Definition raw-utils.h:47
static int spa_format_audio_raw_parse(const struct spa_pod *format, struct spa_audio_info_raw *info)
Definition raw-utils.h:28
Definition param.h:57
Definition param.h:61
#define SPA_PARAM_INFO(id, flags)
Definition param.h:71
Definition raw.h:29
@ SPA_PROP_volume
a volume (Float), 0.0 silence, 1.0 no attenutation
Definition props.h:67
the expected maximum size the meta (Int)
Definition buffers.h:39
the metadata, one of enum spa_meta_type (Id enum spa_meta_type)
Definition buffers.h:38
Definition format.h:27
@ SPA_PARAM_Format
configured format as SPA_TYPE_OBJECT_Format
Definition param.h:34
allowed metadata for buffers as SPA_TYPE_OBJECT_ParamMeta
Definition param.h:36
configurable IO areas as SPA_TYPE_OBJECT_ParamIO
Definition param.h:37
@ SPA_PARAM_EnumFormat
available formats as SPA_TYPE_OBJECT_Format
Definition param.h:33
@ SPA_PARAM_Buffers
buffer configurations as SPA_TYPE_OBJECT_ParamBuffers
Definition param.h:35
@ SPA_FORMAT_mediaType
media type (Id enum spa_media_type)
Definition format.h:93
sample rate (Int)
Definition format.h:100
@ SPA_FORMAT_mediaSubtype
media subtype (Id enum spa_media_subtype)
Definition format.h:94
audio format, (Id enum spa_audio_format)
Definition format.h:98
number of audio channels (Int)
Definition format.h:101
Definition format.h:38
type ID, uniquely identifies the io area (Id enum spa_io_type)
Definition buffers.h:45
size of the io area (Int)
Definition buffers.h:46
Definition raw.h:74
Definition raw.h:78
Definition raw.h:94
Definition raw.h:106
size of a data block memory (Int)
Definition buffers.h:29
stride of data block memory (Int)
Definition buffers.h:30
number of data blocks per buffer (Int)
Definition buffers.h:28
number of buffers (Int)
Definition buffers.h:27
static int spa_pod_builder_prop(struct spa_pod_builder *builder, uint32_t key, uint32_t flags)
Definition builder.h:450
static int spa_pod_builder_float(struct spa_pod_builder *builder, float val)
Definition builder.h:265
#define SPA_POD_CHOICE_ENUM_Id(n_vals,...)
Definition vararg.h:51
#define SPA_POD_CHOICE_RANGE_Int(def, min, max)
Definition vararg.h:58
static int spa_pod_builder_push_sequence(struct spa_pod_builder *builder, struct spa_pod_frame *frame, uint32_t unit)
Definition builder.h:460
#define SPA_POD_Id(val)
Definition vararg.h:49
static void * spa_pod_builder_pop(struct spa_pod_builder *builder, struct spa_pod_frame *frame)
Definition builder.h:168
static int spa_pod_builder_control(struct spa_pod_builder *builder, uint32_t offset, uint32_t type)
Definition builder.h:471
#define spa_pod_builder_add_object(b, type, id,...)
Definition builder.h:659
static void spa_pod_builder_init(struct spa_pod_builder *builder, void *data, uint32_t size)
Definition builder.h:87
static int spa_pod_builder_push_object(struct spa_pod_builder *builder, struct spa_pod_frame *frame, uint32_t type, uint32_t id)
Definition builder.h:435
#define SPA_POD_Int(val)
Definition vararg.h:54
static int spa_pod_filter(struct spa_pod_builder *b, struct spa_pod **result, const struct spa_pod *pod, const struct spa_pod *filter)
Definition filter.h:431
#define spa_strerror(err)
Definition result.h:49
@ SPA_TYPE_OBJECT_ParamBuffers
Definition type.h:77
Definition type.h:79
Definition type.h:75
Definition type.h:78
Definition type.h:76
#define spa_zero(x)
Definition defs.h:431
Definition defs.h:242
Definition defs.h:92
#define SPA_PTROFF(ptr_, offset_, type_)
Return the address (buffer + offset) as pointer of type.
Definition defs.h:208
Definition defs.h:94
Core events.
Definition core.h:126
A main loop object.
Definition properties.h:33
struct spa_dict dict
dictionary of key/values
Definition properties.h:34
Audio information description.
Definition raw.h:284
A Buffer.
Definition buffer.h:94
struct spa_data * datas
array of data members
Definition buffer.h:98
int32_t stride
stride of valid data
Definition buffer.h:49
uint32_t size
size of valid data.
Definition buffer.h:47
uint32_t offset
offset of valid data.
Definition buffer.h:44
Definition command.h:29
Data for a buffer this stays constant for a buffer.
Definition buffer.h:62
struct spa_chunk * chunk
valid chunk of memory
Definition buffer.h:90
int64_t fd
optional fd for data
Definition buffer.h:86
uint32_t mapoffset
offset to map fd at
Definition buffer.h:87
void * data
optional data pointer
Definition buffer.h:89
uint32_t maxsize
max size of data
Definition buffer.h:88
uint32_t type
memory type, one of enum spa_data_type, when allocating memory, the type contains a bitmask of allowe...
Definition buffer.h:63
Definition dict.h:31
Definition dict.h:39
A list of hooks.
Definition hook.h:339
A hook, contains the structure with functions and the data passed to the functions.
Definition hook.h:350
IO area to exchange buffers.
Definition io.h:78
int32_t status
the status code
Definition io.h:89
uint32_t buffer_id
a buffer id
Definition io.h:90
control stream, io area for SPA_IO_Control and SPA_IO_Notify
Definition io.h:170
Definition list.h:27
Describes essential buffer header metadata such as flags and timestamps.
Definition meta.h:67
Node callbacks.
Definition node.h:232
events from the spa_node.
Definition node.h:176
Node methods.
Definition node.h:327
Definition node.h:41
information about a parameter
Definition param.h:51
Definition builder.h:53
Definition iter.h:27
Definition pod.h:43
Port information structure.
Definition node.h:93
the result of enum_params or port_enum_params.
Definition node.h:152
struct spa_pod * param
the result param
Definition node.h:156
uint32_t next
next index of iteration
Definition node.h:155
uint32_t id
id of parameter
Definition node.h:153