C 阅读「；wav"；使用拖缆的文件

我正在尝试在“C”中实现以下管道：

arif@dev:~/GS_samples/cmd_GS$gst-launch-0.10 filesrc location="../sample_media/M1F1-Alaw-AFsp.wav" ! wavparse ! alawdec ! autoaudiosink

下面是我编写的实现

#include <gst/gst.h>

void on_pad_added(GstElement *src_element, GstPad *src_pad, gpointer data);
static gboolean bus_cb(GstBus *bus, GstMessage *message, gpointer data);

static GMainLoop *loop;

int main(int argc, char **argv) {

    GstElement *pipeline;
    GstElement *src;
    GstElement *dec;
    GstElement *parse;
    GstElement *sink;
    GstBus *bus;

    gst_init(&argc, &argv);

    loop = g_main_loop_new (NULL, FALSE);

    pipeline = gst_pipeline_new("wav_player");

    src = gst_element_factory_make("filesrc","src");
    sink = gst_element_factory_make("autoaudiosink","sink");
    parse = gst_element_factory_make("wavparse","parse");
    dec = gst_element_factory_make("alawdec", "dec");

    gst_bin_add_many (GST_BIN(pipeline), src,parse,dec,sink, NULL);
    g_object_set( G_OBJECT (src) , "location",argv[1], NULL);

    gst_element_link(src,parse);
    gst_element_link(dec,sink);
    g_signal_connect (dec, "pad-added", G_CALLBACK (on_pad_added), dec);

    bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));
    gst_bus_add_watch (bus, bus_cb, NULL);
    gst_object_unref(bus);
    gst_element_set_state(pipeline, GST_STATE_PLAYING);
    g_main_loop_run(loop);
    return 0;

}

void on_pad_added (GstElement *src_element, GstPad *src_pad, gpointer data) 
{
    g_print ("linking dynamic pad ...\n");

    GstElement *sink_element = (GstElement *) data;
    GstPad *sink_pad = gst_element_get_static_pad(sink_element, "sink");
    gst_pad_link (src_pad, sink_pad);
    gst_object_unref(sink_pad);

}

static gboolean bus_cb(GstBus *bus, GstMessage *message, gpointer    data)
{
  g_print ("Got %s message\n", GST_MESSAGE_TYPE_NAME (message));

  switch (GST_MESSAGE_TYPE (message)) {
    case GST_MESSAGE_ERROR: {
      GError *err;
      gchar *debug;

      gst_message_parse_error (message, &err, &debug);
      g_print ("Error: %s\n", err->message);
      g_error_free (err);
      g_free (debug);

      g_main_loop_quit (loop);
      break;
    }
    case GST_MESSAGE_EOS:
      /* end-of-stream */
      g_main_loop_quit (loop);
      break;
    default:
      /* unhandled message */
      break;
  }

  /* we want to be notified again the next time there is a message
   * on the bus, so returning TRUE (FALSE means we want to stop watching
   * for messages on the bus and our callback should not be called again)
   */
  return TRUE;
}

---

问题出在这一行：

gst_element_link(src,parse);
gst_element_link(dec,sink);

您试图构建一个管道来为您执行一项任务，但没有正确链接它们。您应该使用：

gst\u元素\u链接\u许多（src、parse、dec、sink）

注意这些元素的顺序很重要，一个元素的输出就是另一个元素的输入

编辑：您还有另外两个问题，我刚刚修改过，它正在工作：

你为什么用解码器？您已经在解析.wav文件，请删除解码器元素，并将数据流传输到audiosink进行播放

代码中没有任何地方将管道设置为播放状态。添加以下代码块以将管道设置为播放状态：

gststatechangereret；
ret=gst\u元素\u集合\u状态（管道、gst\u状态\u播放）；
如果（ret==GST\u状态\u变化\u失败）{
g_printerr（“无法将管道设置为播放状态。\n”）；
gst_对象_unref（管道）；
返回-1；
}

gst_element_link(src,parse);
gst_element_link(dec,sink);