c++ - gstreamer 代码无法链接所有 GST 元素

Question

Ubuntu 14.04Gstreamer 0.10代码 SDK:Qt。

我对 Gstreamer 很陌生。当我在我的终端上使用 gst-launch 工具时，我可以成功地看到连接到我的工作站的摄像头捕获和流式传输视频。

为了继续前进，我已经在 Qt 中编写了 C 代码。它编译正确，当我运行它时，它打开新的 Xterm 窗口并抛出错误“Elements could not be linked” 是我做错了还是我需要做其他事情来查看流媒体

下面是我的代码(它很大程度上受到了其他人代码的启发)

.Pro 文件

QT       += core

QT       -= gui
QT       += core gui
QT       += network
QT           +=core

QMAKE_CXXFLAGS+= -std=c++11
QMAKE_LFLAGS +=  -std=c++11

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets



TARGET = justtest

PKGCONFIG +=glib-2.0
PKGCONFIG += gstreamer-0.10
CONFIG += link_pkgconfig
CONFIG   += console
CONFIG   -= app_bundle


TEMPLATE = app
INCLUDEPATH += pkg-config --cflags glib-2.0
INCLUDEPATH += /usr/include/glib-2.0/glib/
INCLUDEPATH +=/usr/include/libxml2/
INCLUDEPATH += /usr/include/gstreamer-0.10/
SOURCES += main.cpp

主要.cpp

#include <gst/gst.h>
#include <glib.h>


static gboolean bus_call (GstBus *bus, GstMessage *msg, gpointer data)
{
  GMainLoop *loop = (GMainLoop *) data;

  switch (GST_MESSAGE_TYPE (msg)) {

    case GST_MESSAGE_EOS:
      g_print ("End of stream\n");
      g_main_loop_quit (loop);
      break;

    case GST_MESSAGE_ERROR: {
      gchar  *debug;
      GError *error;

      gst_message_parse_error (msg, &error, &debug);
      g_free (debug);

      g_printerr ("Error: %s\n", error->message);
      g_error_free (error);

      g_main_loop_quit (loop);
      break;
    }
    default:
      break;
  }

  return TRUE;
}

int main(int argc, char *argv[])
{
  //QApplication app(argc, argv);
  GstElement *pipeline, *source, *sink, *convert, *videoenc;
  GstBus *bus;
  GstMessage *msg;
  GstStateChangeReturn ret;

  GMainLoop *loop;
  // Initialize GStreamer /
  gst_init (&argc, &argv);

  loop = g_main_loop_new( NULL, FALSE );
  // Create the elements
  source = gst_element_factory_make ("v4l2src", "source");
  sink = gst_element_factory_make ("autovideosink", "sink");
  convert =gst_element_factory_make("ffmpegcolorspace","convert");
  videoenc = gst_element_factory_make ("ffdec_mpeg4", "videoenc");
  // Create the empty pipeline
  pipeline = gst_pipeline_new ("test-pipeline");

  if (!pipeline || !source || !sink || !convert)
    {
      g_printerr ("Not all elements could be created.\n");
      return -1;
    }

  //set der source
      g_object_set (G_OBJECT ( source ), "device", "/dev/video0", NULL);

      // we add a message handler
        bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
        gst_bus_add_watch (bus, bus_call, loop);
        gst_object_unref (bus);


  //Build the pipeline
  gst_bin_add_many (GST_BIN (pipeline), source,  convert,videoenc, sink, NULL);
  if (gst_element_link (convert, sink) != TRUE)
    {
      g_printerr ("Elements could not be linked confert sink.\n");
      gst_object_unref (pipeline);
      return -1;
    }


 // if (gst_element_link (source, convert) != TRUE) {
        //  g_printerr ("Elements could not be linked source -convert.\n");
        //  gst_object_unref (pipeline);
         // return -1;
     // }

  if( gst_element_link_many ( source, convert, videoenc, sink,
                             NULL) != TRUE )
    {
       g_printerr ("Elements could not be linked source -convert.\n");
    }

    g_print("Linked all the Elements together\n");
    // Iterate
      g_print ("Running...\n");
      g_main_loop_run (loop);

      // Out of the main loop, clean up nicely
      g_print ("Returned, stopping playback\n");
      gst_element_set_state (pipeline, GST_STATE_NULL);

      g_print ("Deleting pipeline\n");
      gst_object_unref (GST_OBJECT (pipeline));
      return 0;
}

输出:在新的 X 学期窗口上

"Elements could not be linked"
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Answer 1

您似乎试图将同一个元素链接两次，这是不可能的。

您将 convert 链接到 sink，然后在下面的几行中尝试链接 convert !视频!下沉。

只有当您知道您的相机提供 mpeg4 视频时，才能使用解码器(您命名为 videoenc)，否则协商将失败。如果您的相机支持原始格式，只需从管道中删除解码器。

同样，0.10 多年来无人维护且已过时，请考虑迁移到 1.x。