The previous tutorial showed how to build a pipeline automatically. Now we are going to build a pipeline manually by instantiating each element and linking them all together. In the process, we will learn:<\/p>\n
What is a GStreamer element and how to create one.
\n\u4ec0\u4e48\u662f GStreamer \u5143\u4ef6\uff0c\u5982\u4f55\u521b\u5efa\u5b83<\/p>\n<\/li>\n
How to connect elements to each other.
\n\u5982\u4f55\u5c06\u5143\u4ef6\u8fde\u63a5\u8d77\u6765<\/p>\n<\/li>\n
How to customize an element's behavior.
\n\u5982\u4f55\u81ea\u5b9a\u4e49\u4e00\u4e2a\u5143\u4ef6\u7684\u884c\u4e3a<\/p>\n<\/li>\n
How to watch the bus for error conditions and extract information from GStreamer messages.
\n\u5982\u4f55\u89c2\u5bdf\u603b\u7ebf\u4e0a\u53d1\u751f\u7684\u9519\u8bef\uff0c\u4ece GstMessage \u4e2d\u63d0\u53d6\u4fe1\u606f<\/p>\n<\/li>\n<\/ul>\n
#include <gst\/gst.h>\n\n#ifdef __APPLE__\n#include <TargetConditionals.h>\n#endif\n\nint\ntutorial_main (int argc, char *argv[])\n{\n GstElement *pipeline, *source, *sink;\n GstBus *bus;\n GstMessage *msg;\n GstStateChangeReturn ret;\n\n \/* Initialize GStreamer *\/\n gst_init (&argc, &argv);\n\n \/* Create the elements *\/\n source = gst_element_factory_make ("videotestsrc", "source");\n sink = gst_element_factory_make ("autovideosink", "sink");\n\n \/* Create the empty pipeline *\/\n pipeline = gst_pipeline_new ("test-pipeline");\n\n if (!pipeline || !source || !sink) {\n g_printerr ("Not all elements could be created.\\n");\n return -1;\n }\n\n \/* Build the pipeline *\/\n gst_bin_add_many (GST_BIN (pipeline), source, sink, NULL);\n if (gst_element_link (source, sink) != TRUE) {\n g_printerr ("Elements could not be linked.\\n");\n gst_object_unref (pipeline);\n return -1;\n }\n\n \/* Modify the source's properties *\/\n g_object_set (source, "pattern", 0, NULL);\n\n \/* Start playing *\/\n ret = gst_element_set_state (pipeline, GST_STATE_PLAYING);\n if (ret == GST_STATE_CHANGE_FAILURE) {\n g_printerr ("Unable to set the pipeline to the playing state.\\n");\n gst_object_unref (pipeline);\n return -1;\n }\n\n \/* Wait until error or EOS *\/\n bus = gst_element_get_bus (pipeline);\n msg =\n gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE,\n GST_MESSAGE_ERROR | GST_MESSAGE_EOS);\n\n \/* Parse message *\/\n if (msg != NULL) {\n GError *err;\n gchar *debug_info;\n\n switch (GST_MESSAGE_TYPE (msg)) {\n case GST_MESSAGE_ERROR:\n gst_message_parse_error (msg, &err, &debug_info);\n g_printerr ("Error received from element %s: %s\\n",\n GST_OBJECT_NAME (msg->src), err->message);\n g_printerr ("Debugging information: %s\\n",\n debug_info ? debug_info : "none");\n g_clear_error (&err);\n g_free (debug_info);\n break;\n case GST_MESSAGE_EOS:\n g_print ("End-Of-Stream reached.\\n");\n break;\n default:\n \/* We should not reach here because we only asked for ERRORs and EOS *\/\n g_printerr ("Unexpected message received.\\n");\n break;\n }\n gst_message_unref (msg);\n }\n\n \/* Free resources *\/\n gst_object_unref (bus);\n gst_element_set_state (pipeline, GST_STATE_NULL);\n gst_object_unref (pipeline);\n return 0;\n}\n\nint\nmain (int argc, char *argv[])\n{\n#if defined(__APPLE__) && TARGET_OS_MAC && !TARGET_OS_IPHONE\n return gst_macos_main (tutorial_main, argc, argv, NULL);\n#else\n return tutorial_main (argc, argv);\n#endif\n}\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"Goal The previous tutorial showed how to build a pipeline automatically. Now we are going to build a pipeline manually by instantiating each element and linking them all together. In the process, we will learn: What is a GStreamer element and how to create one. \u4ec0\u4e48\u662f GStreamer \u5143\u4ef6\uff0c\u5982\u4f55\u521b\u5efa\u5b83 How to connect elements to each other. […] →Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1202","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/1202"}],"collection":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1202"}],"version-history":[{"count":1,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/1202\/revisions"}],"predecessor-version":[{"id":1203,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/1202\/revisions\/1203"}],"wp:attachment":[{"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1202"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1202"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.fanyamin.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1202"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}