运行结果
简介
上一个教程演示了如何自动构建管道。如今 我们将通过实例化每个元素来手动构建管道 并将它们全部链接在一起。在此过程中,我们将学习:
• 什么是 GStreamer 元素以及如何创建一个。
• 如何将元素相互连接。
• 如何自定义元素的举动。
• 如何观察总线的错误条件并提取信息 来自 GStreamer 消息。
这些元素是 GStreamer 的根本构造块。他们处理 数据从源元素(数据生产者)流向下游 传递给 sink 元素(数据使用者),通过 filter 元素。
GStreamer相干运行库
- INCLUDEPATH += D:/Software/GStreamer/1.0/mingw_x86_64/include/gstreamer-1.0/gst
- INCLUDEPATH += D:/Software/GStreamer/1.0/mingw_x86_64/include
- INCLUDEPATH += D:/Software/GStreamer/1.0/mingw_x86_64/include/gstreamer-1.0
- INCLUDEPATH += D:/Software/GStreamer/1.0/mingw_x86_64/include/glib-2.0
- INCLUDEPATH += D:/Software/GStreamer/1.0/mingw_x86_64/lib/glib-2.0/include
- LIBS += D:/Software/GStreamer/1.0/mingw_x86_64/lib/gstreamer-1.0.lib
- LIBS += D:/Software/GStreamer/1.0/mingw_x86_64/lib/glib-2.0.lib
- LIBS += D:/Software/GStreamer/1.0/mingw_x86_64/lib/gobject-2.0.lib
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完备源码
- #include <QCoreApplication>
- #include <QDebug>
- #include "gst.h"
- int tutorial_main()
- {
- GstBus *bus;
- GstMessage *msg;
- GstStateChangeReturn ret;
- /* 初始化GStreamer */
- gst_init (nullptr,nullptr);
- /* 创建元素 */
- GstElement *source = gst_element_factory_make ("videotestsrc", "source"); // 元素输出
- GstElement *sink = gst_element_factory_make ("autovideosink", "sink"); // 元素输入
- /* 创建空管道 */
- GstElement *pipeline = gst_pipeline_new ("test-pipeline");
- if (!pipeline || !source || !sink) {g_printerr ("Not all elements could be created.\n");return -1;}
- /* 构建管道 */
- gst_bin_add_many (GST_BIN (pipeline), source, sink, NULL);
- if (gst_element_link (source, sink) != TRUE)
- {
- g_printerr ("无法链接元素.\n");
- gst_object_unref (pipeline); return -1;
- }
- /* 修改元素的属性 */
- g_object_set (source, "pattern", 1, NULL);
- /* 开始播放 */
- ret = gst_element_set_state (pipeline, GST_STATE_PLAYING);
- if (ret == GST_STATE_CHANGE_FAILURE)
- {
- g_printerr ("无法将管道设置为播放状态.\n");
- gst_object_unref (pipeline); return -1;
- }
- /* 用于获取与特定元素相关联的消息总线(message bus)函数。
- * 消息总线是用于在管道的不同部分之间传递消息的机制,例如错误、警告、EOS(End Of Stream)事件等。 */
- bus = gst_element_get_bus (pipeline);
- /* 等待错误或流结束,获取并解析消息 */
- msg = gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE, (GstMessageType)(GST_MESSAGE_ERROR | GST_MESSAGE_EOS));
- if (msg != NULL)
- {
- GError *err;
- gchar *debug_info;
- switch (GST_MESSAGE_TYPE (msg))
- {
- case GST_MESSAGE_ERROR:
- gst_message_parse_error (msg, &err, &debug_info);
- g_printerr ("从元素接收到错误 %s: %s\n", GST_OBJECT_NAME (msg->src), err->message);
- g_printerr ("调试信息: %s\n", debug_info ? debug_info : "none");
- g_clear_error (&err);
- g_free (debug_info);
- break;
- case GST_MESSAGE_EOS: g_print ("流已结束.\n"); break;
- default:
- /* 不应该到达这里,因为我们只要求错误和EOS */
- g_printerr ("收到意外消息.\n"); break;
- }
- gst_message_unref (msg);
- }
- /* 释放资源 */
- gst_object_unref (bus);
- gst_element_set_state (pipeline, GST_STATE_NULL);
- gst_object_unref (pipeline);
- return 0;
- }
- int main(int argc, char *argv[])
- {
- QCoreApplication a(argc, argv);
- #if 1
- tutorial_main();
- #else
- gst_init(nullptr,nullptr);
- const gchar *nano_str;
- guint major,minor, micro,nano;
- gst_version(&major, &minor, µ,&nano);
- qDebug() << major << " " << minor << " " << micro << " " << nano;
- #endif
- return a.exec();
- }
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关注
笔者 - jxd
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