gstreamer/subprojects/gst-docs/examples/tutorials/basic-tutorial-8.c
Piotr Brzeziński 3bb8700577 macos: Add wrapper API to run a NSApplication in the main thread
On macOS, a Cocoa event loop is needed in the main thread to ensure
things like opening a GL window work correctly. In the past, this was
patched into glib via Cerbero, but that prevented us from updating it.
This workaround simply runs an NSApplication and then calls the
main function on a secondary thread, allowing GStreamer to correctly
display windows and/or system permission prompts, for example.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3532>
2022-12-13 17:50:32 +00:00

284 lines
10 KiB
C

#include <gst/gst.h>
#include <gst/audio/audio.h>
#include <string.h>
#ifdef __APPLE__
#include <TargetConditionals.h>
#endif
#define CHUNK_SIZE 1024 /* Amount of bytes we are sending in each buffer */
#define SAMPLE_RATE 44100 /* Samples per second we are sending */
/* Structure to contain all our information, so we can pass it to callbacks */
typedef struct _CustomData
{
GstElement *pipeline, *app_source, *tee, *audio_queue, *audio_convert1,
*audio_resample, *audio_sink;
GstElement *video_queue, *audio_convert2, *visual, *video_convert,
*video_sink;
GstElement *app_queue, *app_sink;
guint64 num_samples; /* Number of samples generated so far (for timestamp generation) */
gfloat a, b, c, d; /* For waveform generation */
guint sourceid; /* To control the GSource */
GMainLoop *main_loop; /* GLib's Main Loop */
} CustomData;
/* This method is called by the idle GSource in the mainloop, to feed CHUNK_SIZE bytes into appsrc.
* The idle handler is added to the mainloop when appsrc requests us to start sending data (need-data signal)
* and is removed when appsrc has enough data (enough-data signal).
*/
static gboolean
push_data (CustomData * data)
{
GstBuffer *buffer;
GstFlowReturn ret;
int i;
GstMapInfo map;
gint16 *raw;
gint num_samples = CHUNK_SIZE / 2; /* Because each sample is 16 bits */
gfloat freq;
/* Create a new empty buffer */
buffer = gst_buffer_new_and_alloc (CHUNK_SIZE);
/* Set its timestamp and duration */
GST_BUFFER_TIMESTAMP (buffer) =
gst_util_uint64_scale (data->num_samples, GST_SECOND, SAMPLE_RATE);
GST_BUFFER_DURATION (buffer) =
gst_util_uint64_scale (num_samples, GST_SECOND, SAMPLE_RATE);
/* Generate some psychodelic waveforms */
gst_buffer_map (buffer, &map, GST_MAP_WRITE);
raw = (gint16 *) map.data;
data->c += data->d;
data->d -= data->c / 1000;
freq = 1100 + 1000 * data->d;
for (i = 0; i < num_samples; i++) {
data->a += data->b;
data->b -= data->a / freq;
raw[i] = (gint16) (500 * data->a);
}
gst_buffer_unmap (buffer, &map);
data->num_samples += num_samples;
/* Push the buffer into the appsrc */
g_signal_emit_by_name (data->app_source, "push-buffer", buffer, &ret);
/* Free the buffer now that we are done with it */
gst_buffer_unref (buffer);
if (ret != GST_FLOW_OK) {
/* We got some error, stop sending data */
return FALSE;
}
return TRUE;
}
/* This signal callback triggers when appsrc needs data. Here, we add an idle handler
* to the mainloop to start pushing data into the appsrc */
static void
start_feed (GstElement * source, guint size, CustomData * data)
{
if (data->sourceid == 0) {
g_print ("Start feeding\n");
data->sourceid = g_idle_add ((GSourceFunc) push_data, data);
}
}
/* This callback triggers when appsrc has enough data and we can stop sending.
* We remove the idle handler from the mainloop */
static void
stop_feed (GstElement * source, CustomData * data)
{
if (data->sourceid != 0) {
g_print ("Stop feeding\n");
g_source_remove (data->sourceid);
data->sourceid = 0;
}
}
/* The appsink has received a buffer */
static GstFlowReturn
new_sample (GstElement * sink, CustomData * data)
{
GstSample *sample;
/* Retrieve the buffer */
g_signal_emit_by_name (sink, "pull-sample", &sample);
if (sample) {
/* The only thing we do in this example is print a * to indicate a received buffer */
g_print ("*");
gst_sample_unref (sample);
return GST_FLOW_OK;
}
return GST_FLOW_ERROR;
}
/* This function is called when an error message is posted on the bus */
static void
error_cb (GstBus * bus, GstMessage * msg, CustomData * data)
{
GError *err;
gchar *debug_info;
/* Print error details on the screen */
gst_message_parse_error (msg, &err, &debug_info);
g_printerr ("Error received from element %s: %s\n",
GST_OBJECT_NAME (msg->src), err->message);
g_printerr ("Debugging information: %s\n", debug_info ? debug_info : "none");
g_clear_error (&err);
g_free (debug_info);
g_main_loop_quit (data->main_loop);
}
int
tutorial_main (int argc, char *argv[])
{
CustomData data;
GstPad *tee_audio_pad, *tee_video_pad, *tee_app_pad;
GstPad *queue_audio_pad, *queue_video_pad, *queue_app_pad;
GstAudioInfo info;
GstCaps *audio_caps;
GstBus *bus;
/* Initialize cumstom data structure */
memset (&data, 0, sizeof (data));
data.b = 1; /* For waveform generation */
data.d = 1;
/* Initialize GStreamer */
gst_init (&argc, &argv);
/* Create the elements */
data.app_source = gst_element_factory_make ("appsrc", "audio_source");
data.tee = gst_element_factory_make ("tee", "tee");
data.audio_queue = gst_element_factory_make ("queue", "audio_queue");
data.audio_convert1 =
gst_element_factory_make ("audioconvert", "audio_convert1");
data.audio_resample =
gst_element_factory_make ("audioresample", "audio_resample");
data.audio_sink = gst_element_factory_make ("autoaudiosink", "audio_sink");
data.video_queue = gst_element_factory_make ("queue", "video_queue");
data.audio_convert2 =
gst_element_factory_make ("audioconvert", "audio_convert2");
data.visual = gst_element_factory_make ("wavescope", "visual");
data.video_convert =
gst_element_factory_make ("videoconvert", "video_convert");
data.video_sink = gst_element_factory_make ("autovideosink", "video_sink");
data.app_queue = gst_element_factory_make ("queue", "app_queue");
data.app_sink = gst_element_factory_make ("appsink", "app_sink");
/* Create the empty pipeline */
data.pipeline = gst_pipeline_new ("test-pipeline");
if (!data.pipeline || !data.app_source || !data.tee || !data.audio_queue
|| !data.audio_convert1 || !data.audio_resample || !data.audio_sink
|| !data.video_queue || !data.audio_convert2 || !data.visual
|| !data.video_convert || !data.video_sink || !data.app_queue
|| !data.app_sink) {
g_printerr ("Not all elements could be created.\n");
return -1;
}
/* Configure wavescope */
g_object_set (data.visual, "shader", 0, "style", 0, NULL);
/* Configure appsrc */
gst_audio_info_set_format (&info, GST_AUDIO_FORMAT_S16, SAMPLE_RATE, 1, NULL);
audio_caps = gst_audio_info_to_caps (&info);
g_object_set (data.app_source, "caps", audio_caps, "format", GST_FORMAT_TIME,
NULL);
g_signal_connect (data.app_source, "need-data", G_CALLBACK (start_feed),
&data);
g_signal_connect (data.app_source, "enough-data", G_CALLBACK (stop_feed),
&data);
/* Configure appsink */
g_object_set (data.app_sink, "emit-signals", TRUE, "caps", audio_caps, NULL);
g_signal_connect (data.app_sink, "new-sample", G_CALLBACK (new_sample),
&data);
gst_caps_unref (audio_caps);
/* Link all elements that can be automatically linked because they have "Always" pads */
gst_bin_add_many (GST_BIN (data.pipeline), data.app_source, data.tee,
data.audio_queue, data.audio_convert1, data.audio_resample,
data.audio_sink, data.video_queue, data.audio_convert2, data.visual,
data.video_convert, data.video_sink, data.app_queue, data.app_sink, NULL);
if (gst_element_link_many (data.app_source, data.tee, NULL) != TRUE
|| gst_element_link_many (data.audio_queue, data.audio_convert1,
data.audio_resample, data.audio_sink, NULL) != TRUE
|| gst_element_link_many (data.video_queue, data.audio_convert2,
data.visual, data.video_convert, data.video_sink, NULL) != TRUE
|| gst_element_link_many (data.app_queue, data.app_sink, NULL) != TRUE) {
g_printerr ("Elements could not be linked.\n");
gst_object_unref (data.pipeline);
return -1;
}
/* Manually link the Tee, which has "Request" pads */
tee_audio_pad = gst_element_request_pad_simple (data.tee, "src_%u");
g_print ("Obtained request pad %s for audio branch.\n",
gst_pad_get_name (tee_audio_pad));
queue_audio_pad = gst_element_get_static_pad (data.audio_queue, "sink");
tee_video_pad = gst_element_request_pad_simple (data.tee, "src_%u");
g_print ("Obtained request pad %s for video branch.\n",
gst_pad_get_name (tee_video_pad));
queue_video_pad = gst_element_get_static_pad (data.video_queue, "sink");
tee_app_pad = gst_element_request_pad_simple (data.tee, "src_%u");
g_print ("Obtained request pad %s for app branch.\n",
gst_pad_get_name (tee_app_pad));
queue_app_pad = gst_element_get_static_pad (data.app_queue, "sink");
if (gst_pad_link (tee_audio_pad, queue_audio_pad) != GST_PAD_LINK_OK ||
gst_pad_link (tee_video_pad, queue_video_pad) != GST_PAD_LINK_OK ||
gst_pad_link (tee_app_pad, queue_app_pad) != GST_PAD_LINK_OK) {
g_printerr ("Tee could not be linked\n");
gst_object_unref (data.pipeline);
return -1;
}
gst_object_unref (queue_audio_pad);
gst_object_unref (queue_video_pad);
gst_object_unref (queue_app_pad);
/* Instruct the bus to emit signals for each received message, and connect to the interesting signals */
bus = gst_element_get_bus (data.pipeline);
gst_bus_add_signal_watch (bus);
g_signal_connect (G_OBJECT (bus), "message::error", (GCallback) error_cb,
&data);
gst_object_unref (bus);
/* Start playing the pipeline */
gst_element_set_state (data.pipeline, GST_STATE_PLAYING);
/* Create a GLib Main Loop and set it to run */
data.main_loop = g_main_loop_new (NULL, FALSE);
g_main_loop_run (data.main_loop);
/* Release the request pads from the Tee, and unref them */
gst_element_release_request_pad (data.tee, tee_audio_pad);
gst_element_release_request_pad (data.tee, tee_video_pad);
gst_element_release_request_pad (data.tee, tee_app_pad);
gst_object_unref (tee_audio_pad);
gst_object_unref (tee_video_pad);
gst_object_unref (tee_app_pad);
/* Free resources */
gst_element_set_state (data.pipeline, GST_STATE_NULL);
gst_object_unref (data.pipeline);
return 0;
}
int
main (int argc, char *argv[])
{
#if defined(__APPLE__) && TARGET_OS_MAC && !TARGET_OS_IPHONE
return gst_macos_main (tutorial_main, argc, argv, NULL);
#else
return tutorial_main (argc, argv);
#endif
}