GStreamer教程01
阿新 • • 發佈:2018-11-07
參考來自 <http://blog.csdn.net/sakulafly/article/details/19398257>,並整理。
gst_parse_launch
GStreamer是設計來處理多媒體流的框架。媒體流經過一系列的中間element,從source element流到sink element。這些相互作用的element構成了一整個的pipeline。
使用GStreamer時你常常需要使用獨立的elements來手動搭建一個pipeline,但是,在比較簡單的情況下,我們也可以使用gst_parse_launch()。這個函式原本是描述一個pipeline的,但也可以很方便的用來建立一個pipeline。
來自 <http://blog.csdn.net/sakulafly/article/details/19398257>
playbin2
playbin2是一個特殊的element,它既是一個source也是一個sink,同時也能處理整個pipeline的事務。在內部,他建立和連結了所有播放你的媒體所必須的elements,你完全不必擔心。
1. /* Build the pipeline */
2. pipeline = gst_parse_launch ("playbin2 uri=http://docs.gstreamer.com/media/sintel_trailer-480p.webm",
//僅解析了playbin2得一個引數——我們希望播放的URI。試試其他的地址,比如http://或者file://開頭的URI,playbin2都能良好的工作。
#include<gst/gst.h> intmain(int argc, char *argv[]) { GstElement *pipeline, *source, *sink; GstBus *bus; GstMessage *msg; GstStateChangeReturn ret; /* Initialize GStreamer */ gst_init (&argc, &argv); /*Create the elements */ //gst_element_factory_make引數(element型別,element名字) source = gst_element_factory_make("videotestsrc", "source"); sink = gst_element_factory_make("autovideosink", "sink"); /* Create the emptypipeline */ pipeline = gst_pipeline_new("test-pipeline"); if (!pipeline || !source || !sink) { g_printerr ("Not all elements could becreated.\n"); return -1; } /* Build the pipeline */ //一個pipeline就是一個特定型別的可以包含其他element的bin,而且所以可 以用在bin上的方法也都可以用在pipeline上。 //向pipeline新增element,由null終止,【gst_bin_add增加單個】 gst_bin_add_many (GST_BIN (pipeline),source, sink, NULL); //gst_element_link連線bin裡面的element(源,目標) if (gst_element_link (source, sink) !=TRUE) { g_printerr ("Elements could not belinked.\n"); gst_object_unref (pipeline); return-1; } /* Modify the source's properties */ //g_object_set()方法接受一個用NULL結束的屬性名稱/屬性值的組成的對,所以可以一次同時修改多項屬性。 g_object_set (source, "pattern", 0,NULL); /* Start playing */ ret = gst_element_set_state (pipeline, GST_STATE_PLAYING); if (ret == GST_STATE_CHANGE_FAILURE) { g_printerr ("Unable to set thepipeline to the playing state.\n"); gst_object_unref (pipeline); return -1; } /* Wait until error or EOS */ //gst_bus_timed_pop_filtered會阻塞知道獲得一個訊息 bus = gst_element_get_bus (pipeline); msg = gst_bus_timed_pop_filtered (bus,GST_CLOCK_TIME_NONE, GST_MESSAGE_ERROR | GST_MESSAGE_EOS); /* Parse message */ 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 ("Error received from element%s: %s\n", GST_OBJECT_NAME (msg->src), err->message); g_printerr ("Debugginginformation: %s\n", debug_info ? debug_info : "none"); g_clear_error (&err); g_free (debug_info); break; case GST_MESSAGE_EOS: g_print ("End-Of-Streamreached.\n"); break; default: /* We should not reach here because weonly asked for ERRORs and EOS */ g_printerr ("Unexpected messagereceived.\n"); break; } gst_message_unref (msg); } /* Free resources */ gst_object_unref (bus); gst_element_set_state (pipeline,GST_STATE_NULL); gst_object_unref (pipeline); return 0; }