大家好我正在尝试使用c中的gstreamer库来改变音频文件的播放速度。我已经关注了gstreamer网站上的大部分教程，但唯一不起作用的是播放速度。
现在它的设置方式，当'。'时速度应加倍。遇到但没有任何反应。任何有经验的gstreamer用户都可以提供一些见解吗？
typedef struct bindata {
GMainLoop *loop;
GstElement *pipeline, *source, *mp3decoder, *volume, *pulseout;
gboolean playing;
} bindata;
static bindata data;
static gboolean bus_call(GstBus *bus, GstMessage *msg, gpointer *misc){
//GMainLoop *loop = (GMainLoop *) misc;
switch (GST_MESSAGE_TYPE(msg)){
case GST_MESSAGE_EOS: {
g_message("End of stream.\n");
g_main_loop_quit(data.loop);
break;
}
case GST_MESSAGE_ERROR:{
GError *error;
gst_message_parse_error(msg, &error, NULL);
g_printerr("%s\n", error->message);
g_error_free(error);
g_main_loop_quit(data.loop);
break;
}
default: break;
}
return TRUE;
}
static gboolean keypress (GIOChannel *src, GIOCondition cond, bindata *data){
int c;
gdouble vol;
GstFormat format = GST_FORMAT_TIME;
//if(g_io_channel_read_unichar(src, str, NULL) != G_IO_STATUS_NORMAL){
if((c = getchar()) == EOF ){
return TRUE;
}
switch(c){
case '+':
g_object_get(data->volume, "volume", &vol,NULL);
if (vol >= 10) break;
g_object_set (data->volume, "volume", vol + 0.1, NULL);
break;
case '-':
g_object_get(data->volume, "volume", &vol, NULL);
if (vol <= 0.1) break;
g_object_set (data->volume, "volume", vol - 0.1, NULL);
break;
case '.':
g_print("speed up \n");
gst_element_send_event(data->pulseout, gst_event_new_step(format, 20, 2.0, TRUE, FALSE));
break;
case ',':
g_print("speed down \n");
break;
case ' ':
data->playing = !data->playing;
gst_element_set_state (data->pipeline, data->playing ? GST_STATE_PLAYING : GST_STATE_PAUSED);
break;
default:
break;
}
return TRUE;
}
int main(int argc, char *argv[]){
GstBus *bus;
guint bus_watch_id;
GIOChannel *io_stdin;
gst_init(&argc, &argv);
memset (&data, 0, sizeof(data));
data.loop = g_main_loop_new(NULL, false);
if(argc != 2){
g_printerr("Usage: ./play <URI: mp3 file>");
return -1;
}
io_stdin = g_io_channel_unix_new (fileno (stdin));
g_io_add_watch (io_stdin, G_IO_IN, (GIOFunc) keypress, &data);
data.pipeline = gst_pipeline_new ("audio-player");
data.source = gst_element_factory_make ("filesrc", "file source");
data.mp3decoder = gst_element_factory_make ("mad", "mad mp3");
data.volume = gst_element_factory_make ("volume", "volume");
data.pulseout = gst_element_factory_make ("pulsesink", "pulse audio");
if(!data.pipeline || !data.source || !data.mp3decoder || !data.pulseout || !data.volume) {
g_printerr("Some element(s) could not be created. Exiting. \n");
return -1;
}
g_object_set (G_OBJECT (data.source), "location", argv[1], NULL);
g_object_set (G_OBJECT(data.volume), "volume", 0.01, NULL);
bus = gst_pipeline_get_bus(GST_PIPELINE(data.pipeline));
bus_watch_id = gst_bus_add_watch(bus, bus_call, NULL);
gst_object_unref(bus);
gst_bin_add_many(GST_BIN (data.pipeline), data.source, data.mp3decoder, data.volume, data.pulseout, NULL);
gst_element_link_many (data.source, data.mp3decoder, data.volume, data.pulseout, NULL);
gst_element_set_state(data.pipeline, GST_STATE_PLAYING);
data.playing = TRUE;
g_print ("Running...\n");
g_main_loop_run(data.loop);
g_print ("ended. \n");
gst_element_set_state(data.pipeline, GST_STATE_NULL);
gst_object_unref(GST_OBJECT(data.pipeline));
g_source_remove (bus_watch_id);
g_main_loop_unref (data.loop);
return 0;
}
答案 0 :(得分：0)
通过设置rate属性，通过gst_event_new_seek或gst_element_seek搜索控制播放速度，请参阅https://developer.gnome.org/gstreamer/stable/gstreamer-GstEvent.html#gst-event-new-seek和http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/GstElement.html#gst-element-seek
上的文档答案 1 :(得分：0)
the following, while oriented on video rather than audio,
shows how to change the playback speed.
it is from:
<http://docs.gstreamer.com/display/GstSDK/Basic+tutorial+13%3A+Playback+speed>
#include <string.h>
#include <gst/gst.h>
typedef struct _CustomData {
GstElement *pipeline;
GstElement *video_sink;
GMainLoop *loop;
gboolean playing; /* Playing or Paused */
gdouble rate; /* Current playback rate (can be negative) */
} CustomData;
/* Send seek event to change rate */
static void send_seek_event (CustomData *data) {
gint64 position;
GstFormat format = GST_FORMAT_TIME;
GstEvent *seek_event;
/* Obtain the current position, needed for the seek event */
if (!gst_element_query_position (data->pipeline, &format, &position)) {
g_printerr ("Unable to retrieve current position.\n");
return;
}
/* Create the seek event */
if (data->rate > 0) {
seek_event = gst_event_new_seek (data->rate, GST_FORMAT_TIME, GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_ACCURATE,
GST_SEEK_TYPE_SET, position, GST_SEEK_TYPE_NONE, 0);
} else {
seek_event = gst_event_new_seek (data->rate, GST_FORMAT_TIME, GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_ACCURATE,
GST_SEEK_TYPE_SET, 0, GST_SEEK_TYPE_SET, position);
}
if (data->video_sink == NULL) {
/* If we have not done so, obtain the sink through which we will send the seek events */
g_object_get (data->pipeline, "video-sink", &data->video_sink, NULL);
}
/* Send the event */
gst_element_send_event (data->video_sink, seek_event);
g_print ("Current rate: %g\n", data->rate);
}
/* Process keyboard input */
static gboolean handle_keyboard (GIOChannel *source, GIOCondition cond, CustomData *data) {
gchar *str = NULL;
if (g_io_channel_read_line (source, &str, NULL, NULL, NULL) != G_IO_STATUS_NORMAL) {
return TRUE;
}
switch (g_ascii_tolower (str[0])) {
case 'p':
data->playing = !data->playing;
gst_element_set_state (data->pipeline, data->playing ? GST_STATE_PLAYING : GST_STATE_PAUSED);
g_print ("Setting state to %s\n", data->playing ? "PLAYING" : "PAUSE");
break;
case 's':
if (g_ascii_isupper (str[0])) {
data->rate *= 2.0;
} else {
data->rate /= 2.0;
}
send_seek_event (data);
break;
case 'd':
data->rate *= -1.0;
send_seek_event (data);
break;
case 'n':
if (data->video_sink == NULL) {
/* If we have not done so, obtain the sink through which we will send the step events */
g_object_get (data->pipeline, "video-sink", &data->video_sink, NULL);
}
gst_element_send_event (data->video_sink,
gst_event_new_step (GST_FORMAT_BUFFERS, 1, data->rate, TRUE, FALSE));
g_print ("Stepping one frame\n");
break;
case 'q':
g_main_loop_quit (data->loop);
break;
default:
break;
}
g_free (str);
return TRUE;
}
int main(int argc, char *argv[]) {
CustomData data;
GstStateChangeReturn ret;
GIOChannel *io_stdin;
/* Initialize GStreamer */
gst_init (&argc, &argv);
/* Initialize our data structure */
memset (&data, 0, sizeof (data));
/* Print usage map */
g_print (
"USAGE: Choose one of the following options, then press enter:\n"
" 'P' to toggle between PAUSE and PLAY\n"
" 'S' to increase playback speed, 's' to decrease playback speed\n"
" 'D' to toggle playback direction\n"
" 'N' to move to next frame (in the current direction, better in PAUSE)\n"
" 'Q' to quit\n");
/* Build the pipeline */
data.pipeline = gst_parse_launch ("playbin2 uri=http://docs.gstreamer.com/media/sintel_trailer-480p.webm", NULL);
/* Add a keyboard watch so we get notified of keystrokes */
#ifdef _WIN32
io_stdin = g_io_channel_win32_new_fd (fileno (stdin));
#else
io_stdin = g_io_channel_unix_new (fileno (stdin));
#endif
g_io_add_watch (io_stdin, G_IO_IN, (GIOFunc)handle_keyboard, &data);
/* Start playing */
ret = gst_element_set_state (data.pipeline, GST_STATE_PLAYING);
if (ret == GST_STATE_CHANGE_FAILURE) {
g_printerr ("Unable to set the pipeline to the playing state.\n");
gst_object_unref (data.pipeline);
return -1;
}
data.playing = TRUE;
data.rate = 1.0;
/* Create a GLib Main Loop and set it to run */
data.loop = g_main_loop_new (NULL, FALSE);
g_main_loop_run (data.loop);
/* Free resources */
g_main_loop_unref (data.loop);
g_io_channel_unref (io_stdin);
gst_element_set_state (data.pipeline, GST_STATE_NULL);
if (data.video_sink != NULL)
gst_object_unref (data.video_sink);
gst_object_unref (data.pipeline);
return 0;
}