与Qt和Gstreamer的交互问题

我在Qt中有我的GUI，我有一个Gstreamer管道，它从电视FM卡抓取音频并将其写入文件。我在管道中添加了一个level元素，因为我想使用Qt ProgressBar显示当前的音频级别。我只是无法弄清楚如何将GLib contexto的值传递给Qt GUI上下文。与Qt和Gstreamer的交互问题

一块我的代码，我添加总线手表（Qt的插槽内）

gst_bin_add_many(GST_BIN(pline2), alsasrc, audioconvert, level, audioresample, wavenc, filesink, NULL); 
gst_element_link_many(alsasrc, audioconvert, level, audioresample, wavenc, filesink, NULL); 
bus = gst_pipeline_get_bus(GST_PIPELINE(pline2)); 
guint watch_id = gst_bus_add_watch (bus, message_handler, NULL); 
gst_bus_add_watch(bus, bus_call, loop2); 
gst_object_unref(bus);

而这正是我得到的音频电平

static gboolean message_handler (GstBus * bus, GstMessage * message, gpointer data) 
{ 
    if (message->type == GST_MESSAGE_ELEMENT) { 
     const GstStructure *s = gst_message_get_structure (message); 
     const gchar *name = gst_structure_get_name (s); 
     if (strcmp (name, "level") == 0) { 
      gint channels; 
      GstClockTime endtime; 
      gdouble rms_dB, peak_dB, decay_dB; 
      gdouble rms; 
      const GValue *array_val; 
      const GValue *value; 
      GValueArray *rms_arr, *peak_arr, *decay_arr; 
      gint i; 
      if (!gst_structure_get_clock_time (s, "endtime", &endtime)) 
       g_warning ("Could not parse endtime"); 
      /* the values are packed into GValueArrays with the value per channel */ 
      array_val = gst_structure_get_value (s, "rms"); 
      rms_arr = (GValueArray *) g_value_get_boxed (array_val); 
      array_val = gst_structure_get_value (s, "peak"); 
      peak_arr = (GValueArray *) g_value_get_boxed (array_val); 
      array_val = gst_structure_get_value (s, "decay"); 
      decay_arr = (GValueArray *) g_value_get_boxed (array_val); 
      /* we can get the number of channels as the length of any of the value 
        * arrays */ 
      channels = rms_arr->n_values; 
      g_print ("endtime: %" GST_TIME_FORMAT ", channels: %d\n", 
         GST_TIME_ARGS (endtime), channels); 
      for (i = 0; i < channels; ++i) { 
       g_print ("channel %d\n", i); 
       value = g_value_array_get_nth (rms_arr, i); 
       rms_dB = g_value_get_double (value); 
       value = g_value_array_get_nth (peak_arr, i); 
       peak_dB = g_value_get_double (value); 
       value = g_value_array_get_nth (decay_arr, i); 
       decay_dB = g_value_get_double (value); 
       //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); 


      } 
     } 
    } 
    return TRUE; 
}

我怎么能显示，对于例如，rms_dB值？也许有人可以给我一个提示。谢谢。

来源

2017-09-15 alexanderk409

您可以通过进度条指针作为参数传递给gst_bus_add_watch：

QProgressBar* progressBar = ...; 
... 
guint watch_id = gst_bus_add_watch (bus, message_handler, (gpointer)progressBar); 
... 
static gboolean message_handler (GstBus * bus, GstMessage * message, gpointer data) 
{ 
    ... 
    QProgressBar* progressBar = static_cast<QProgressBar*>(data); 
    progressBar->setValue(rms_dB); 
    ... 
}

来源

2017-09-15 16:14:43

这是我所得到的：错误：调用没有匹配的函数“qobject_cast（无效*）” QProgressBar *进度= qobject_cast （数据）; – alexanderk409

QProgressBar * progressBar = static_cast （data）;,因为不是QObject指针qobject_cast不能工作。 –

非常感谢。辉煌的解决方案。有用。 – alexanderk409

与Qt和Gstreamer的交互问题

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