gstreamer

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gstreamer

可以通过appsrc将外部的数据添加到gstreamer 的 pipeline中，下面链接是appsrc 的一些说明（可能需要翻墙才能打开，其中还有appsink的一些说明和例子）

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下面是其中的一例子

#include <gst/gst.h>static GMainLoop *loop;static void
cb_need_data (GstElement *appsrc,guint       unused_size,gpointer    user_data)
{static gboolean white = FALSE;static GstClockTime timestamp = 0;GstBuffer *buffer;guint size;GstFlowReturn ret;size = 385 * 288 * 2;buffer = gst_buffer_new_allocate (NULL, size, NULL);/* this makes the image black/white */gst_buffer_memset (buffer, 0, white ? 0xff : 0x0, size);white = !white;GST_BUFFER_PTS (buffer) = timestamp;GST_BUFFER_DURATION (buffer) = gst_util_uint64_scale_int (1, GST_SECOND, 2);timestamp += GST_BUFFER_DURATION (buffer);g_signal_emit_by_name (appsrc, "push-buffer", buffer, &ret);gst_buffer_unref (buffer);if (ret != GST_FLOW_OK) {/* something wrong, stop pushing */g_main_loop_quit (loop);}
}gint
main (gint   argc,gchar *argv[])
{GstElement *pipeline, *appsrc, *conv, *videosink;/* init GStreamer */gst_init (&argc, &argv);loop = g_main_loop_new (NULL, FALSE);/* setup pipeline */pipeline = gst_pipeline_new ("pipeline");appsrc = gst_element_factory_make ("appsrc", "source");conv = gst_element_factory_make ("videoconvert", "conv");videosink = gst_element_factory_make ("xvimagesink", "videosink");/* setup */g_object_set (G_OBJECT (appsrc), "caps",gst_caps_new_simple ("video/x-raw","format", G_TYPE_STRING, "RGB16","width", G_TYPE_INT, 384,"height", G_TYPE_INT, 288,"framerate", GST_TYPE_FRACTION, 0, 1,NULL), NULL);gst_bin_add_many (GST_BIN (pipeline), appsrc, conv, videosink, NULL);gst_element_link_many (appsrc, conv, videosink, NULL);/* setup appsrc */g_object_set (G_OBJECT (appsrc),"stream-type", 0,"format", GST_FORMAT_TIME, NULL);g_signal_connect (appsrc, "need-data", G_CALLBACK (cb_need_data), NULL);/* play */gst_element_set_state (pipeline, GST_STATE_PLAYING);g_main_loop_run (loop);/* clean up */gst_element_set_state (pipeline, GST_STATE_NULL);gst_object_unref (GST_OBJECT (pipeline));g_main_loop_unref (loop);return 0;}

gstreamer也可以和opencv中mat链接起来，将下面的代码替换掉cb_need_data函数中相应的部分就可以了
 GstMapInfo map;
  gst_buffer_map(buffer,&map,GST_MAP_READ);
  memcpy(map.data,ptr->input->data,size);   //ptr->input 即一个mat指针
  GST_BUFFER_PTS (buffer) = timestamp;
  GST_BUFFER_DURATION (buffer) = gst_util_uint64_scale_int (1, GST_SECOND, 25);
  timestamp += GST_BUFFER_DURATION (buffer) ;
  g_signal_emit_by_name (appsrc, "push-buffer", buffer, &ret);
  gst_buffer_unmap(buffer,&map);
  gst_buffer_unref (buffer);

最后的gst_buffer_unmap()和gst_buffer_rnref()是释放内存空间，缺少的话会导致随着运行时间占用的内存会无限增长。

本文标签： GStreamer