1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
|
#include <string.h>
#include <math.h>
#include <gst/gst.h>
gboolean
message_handler (GstBus * bus, GstMessage * message, gpointer data)
{
if (message->type == GST_MESSAGE_APPLICATION) {
const GstStructure *s = gst_message_get_structure (message);
const gchar *name = gst_structure_get_name (s);
if (strcmp (name, "level") == 0) {
gint channels;
gdouble endtime, rms_dB, peak_dB, decay_dB;
gdouble rms;
const GValue *list;
const GValue *value;
if (!gst_structure_get_double (s, "endtime", &endtime))
g_warning ("Could not parse endtime");
list = gst_structure_get_value (s, "rms");
/* we can get the number of channels as the length of any of the value
* lists */
channels = gst_value_list_get_size (list);
/* we will only get values for the first channel, since we know sinesrc
* is mono */
value = gst_value_list_get_value (list, 0);
rms_dB = g_value_get_double (value);
list = gst_structure_get_value (s, "peak");
value = gst_value_list_get_value (list, 0);
peak_dB = g_value_get_double (value);
list = gst_structure_get_value (s, "decay");
value = gst_value_list_get_value (list, 0);
decay_dB = g_value_get_double (value);
g_print ("endtime: %f, channels: %d\n", endtime, channels);
g_print ("RMS: %f dB, peak: %f dB, decay: %f dB\n",
rms_dB, peak_dB, decay_dB);
/* converting from dB to normal gives us a value between 0.0 and 1.0 */
rms = pow (10, rms_dB / 20);
g_print ("normalized rms value: %f\n", rms);
}
}
/* we handled the message we want, and ignored the ones we didn't want.
* so the core can unref the message for us */
return TRUE;
}
int
main (int argc, char *argv[])
{
GstElement *sinesrc, *level, *fakesink;
GstElement *pipeline;
GstBus *bus;
gint watch_id;
GMainLoop *loop;
gst_init (&argc, &argv);
pipeline = gst_pipeline_new (NULL);
g_assert (pipeline);
sinesrc = gst_element_factory_make ("sinesrc", NULL);
g_assert (sinesrc);
level = gst_element_factory_make ("level", NULL);
g_assert (level);
fakesink = gst_element_factory_make ("fakesink", NULL);
g_assert (fakesink);
gst_bin_add_many (GST_BIN (pipeline), sinesrc, level, fakesink, NULL);
gst_element_link (sinesrc, level);
gst_element_link (level, fakesink);
/* make sure we'll get messages */
g_object_set (G_OBJECT (level), "message", TRUE, NULL);
bus = gst_element_get_bus (pipeline);
watch_id = gst_bus_add_watch (bus, GST_MESSAGE_ANY, message_handler, NULL);
gst_element_set_state (pipeline, GST_STATE_PLAYING);
/* we need to run a GLib main loop to get the messages */
loop = g_main_loop_new (NULL, FALSE);
g_main_loop_run (loop);
return 0;
}
|
