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https://gitlab.freedesktop.org/gstreamer/gstreamer.git
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172 lines
5.2 KiB
C
172 lines
5.2 KiB
C
#include <gst/gst.h>
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#include <gst/audio/audio.h>
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#include <string.h>
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#define CHUNK_SIZE 1024 /* Amount of bytes we are sending in each buffer */
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#define SAMPLE_RATE 44100 /* Samples per second we are sending */
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/* Structure to contain all our information, so we can pass it to callbacks */
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typedef struct _CustomData
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{
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GstElement *pipeline;
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GstElement *app_source;
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guint64 num_samples; /* Number of samples generated so far (for timestamp generation) */
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gfloat a, b, c, d; /* For waveform generation */
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guint sourceid; /* To control the GSource */
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GMainLoop *main_loop; /* GLib's Main Loop */
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} CustomData;
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/* This method is called by the idle GSource in the mainloop, to feed CHUNK_SIZE bytes into appsrc.
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* The ide handler is added to the mainloop when appsrc requests us to start sending data (need-data signal)
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* and is removed when appsrc has enough data (enough-data signal).
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*/
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static gboolean
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push_data (CustomData * data)
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{
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GstBuffer *buffer;
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GstFlowReturn ret;
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int i;
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GstMapInfo map;
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gint16 *raw;
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gint num_samples = CHUNK_SIZE / 2; /* Because each sample is 16 bits */
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gfloat freq;
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/* Create a new empty buffer */
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buffer = gst_buffer_new_and_alloc (CHUNK_SIZE);
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/* Set its timestamp and duration */
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GST_BUFFER_TIMESTAMP (buffer) =
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gst_util_uint64_scale (data->num_samples, GST_SECOND, SAMPLE_RATE);
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GST_BUFFER_DURATION (buffer) =
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gst_util_uint64_scale (num_samples, GST_SECOND, SAMPLE_RATE);
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/* Generate some psychodelic waveforms */
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gst_buffer_map (buffer, &map, GST_MAP_WRITE);
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raw = (gint16 *) map.data;
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data->c += data->d;
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data->d -= data->c / 1000;
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freq = 1100 + 1000 * data->d;
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for (i = 0; i < num_samples; i++) {
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data->a += data->b;
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data->b -= data->a / freq;
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raw[i] = (gint16) (500 * data->a);
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}
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gst_buffer_unmap (buffer, &map);
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data->num_samples += num_samples;
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/* Push the buffer into the appsrc */
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g_signal_emit_by_name (data->app_source, "push-buffer", buffer, &ret);
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/* Free the buffer now that we are done with it */
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gst_buffer_unref (buffer);
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if (ret != GST_FLOW_OK) {
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/* We got some error, stop sending data */
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return FALSE;
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}
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return TRUE;
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}
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/* This signal callback triggers when appsrc needs data. Here, we add an idle handler
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* to the mainloop to start pushing data into the appsrc */
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static void
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start_feed (GstElement * source, guint size, CustomData * data)
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{
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if (data->sourceid == 0) {
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g_print ("Start feeding\n");
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data->sourceid = g_idle_add ((GSourceFunc) push_data, data);
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}
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}
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/* This callback triggers when appsrc has enough data and we can stop sending.
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* We remove the idle handler from the mainloop */
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static void
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stop_feed (GstElement * source, CustomData * data)
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{
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if (data->sourceid != 0) {
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g_print ("Stop feeding\n");
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g_source_remove (data->sourceid);
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data->sourceid = 0;
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}
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}
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/* This function is called when an error message is posted on the bus */
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static void
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error_cb (GstBus * bus, GstMessage * msg, CustomData * data)
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{
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GError *err;
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gchar *debug_info;
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/* Print error details on the screen */
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gst_message_parse_error (msg, &err, &debug_info);
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g_printerr ("Error received from element %s: %s\n",
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GST_OBJECT_NAME (msg->src), err->message);
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g_printerr ("Debugging information: %s\n", debug_info ? debug_info : "none");
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g_clear_error (&err);
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g_free (debug_info);
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g_main_loop_quit (data->main_loop);
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}
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/* This function is called when playbin has created the appsrc element, so we have
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* a chance to configure it. */
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static void
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source_setup (GstElement * pipeline, GstElement * source, CustomData * data)
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{
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GstAudioInfo info;
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GstCaps *audio_caps;
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g_print ("Source has been created. Configuring.\n");
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data->app_source = source;
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/* Configure appsrc */
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gst_audio_info_set_format (&info, GST_AUDIO_FORMAT_S16, SAMPLE_RATE, 1, NULL);
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audio_caps = gst_audio_info_to_caps (&info);
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g_object_set (source, "caps", audio_caps, "format", GST_FORMAT_TIME, NULL);
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g_signal_connect (source, "need-data", G_CALLBACK (start_feed), data);
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g_signal_connect (source, "enough-data", G_CALLBACK (stop_feed), data);
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gst_caps_unref (audio_caps);
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}
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int
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main (int argc, char *argv[])
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{
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CustomData data;
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GstBus *bus;
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/* Initialize cumstom data structure */
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memset (&data, 0, sizeof (data));
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data.b = 1; /* For waveform generation */
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data.d = 1;
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/* Initialize GStreamer */
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gst_init (&argc, &argv);
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/* Create the playbin element */
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data.pipeline = gst_parse_launch ("playbin uri=appsrc://", NULL);
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g_signal_connect (data.pipeline, "source-setup", G_CALLBACK (source_setup),
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&data);
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/* Instruct the bus to emit signals for each received message, and connect to the interesting signals */
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bus = gst_element_get_bus (data.pipeline);
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gst_bus_add_signal_watch (bus);
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g_signal_connect (G_OBJECT (bus), "message::error", (GCallback) error_cb,
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&data);
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gst_object_unref (bus);
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/* Start playing the pipeline */
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gst_element_set_state (data.pipeline, GST_STATE_PLAYING);
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/* Create a GLib Main Loop and set it to run */
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data.main_loop = g_main_loop_new (NULL, FALSE);
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g_main_loop_run (data.main_loop);
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/* Free resources */
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gst_element_set_state (data.pipeline, GST_STATE_NULL);
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gst_object_unref (data.pipeline);
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return 0;
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}
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