我试图执行以下操作：使用gstreamer接收视频流并使用opencv进行处理.我找到了几个解决方案,其中之一是将视频写入(从gstreamer)fifo中,然后使用opencv读取它. (OPTION3这里
MJPEG streaming and decoding).问题是我不能打开管道. cvCreateFileCapture从不返回.这是我写的部分代码：
if(mkfifo("fifo.avi",S_IRUSR| S_IWUSR) == -1)
{
cout<<"Cant create fifo"<<endl;
cout<<errno<<endl;
}
loop = g_main_loop_new(NULL,false);
fsink = gst_element_factory_make("filesink","fsink");
g_object_set(G_OBJECT(fsink),"location","fifo.avi",NULL);
playbin = gst_element_factory_make("playbin2","play");
g_object_set(G_OBJECT(playbin),"uri",uri.c_str(),NULL);
g_object_set(G_OBJECT(playbin),"video-sink",fsink,NULL);
bus = gst_pipeline_get_bus(GST_PIPELINE(playbin));
gst_bus_add_signal_watch(bus);
g_signal_connect(bus,"message::buffering",G_CALLBACK(&set_playbin_state),playbin);
gst_object_unref(bus);
cvNamedWindow("output",CV_WINDOW_AUTOSIZE);
capture = cvCreateFileCapture("fifo.avi");
程序堆栈在最后一行.
PS：我使用的是opencv 2.3.1.
解决方法
所以.搜索一段时间后,我找到了一个解决方案,它涉及从缓冲区检索数据.所以想法是创建播放器并将appsink设置为“视频接收器”.这里是代码示例：
cout<<"Creating appsink"<<endl;
appsink = gst_element_factory_make("appsink","asink");
gst_app_sink_set_emit_signals((GstAppSink*)appsink,true);
gst_app_sink_set_drop((GstAppSink*)appsink,true);
gst_app_sink_set_max_buffers((GstAppSink*)appsink,1);
//creating and initialising pipeline
g_object_set(G_OBJECT(playbin),appsink,NULL);
g_signal_connect(appsink,"new-buffer",G_CALLBACK(DisplayFrame),(gpointer) mark);
//callback function looks like this
gboolean Core::DisplayFrame(GstAppSink *fks,gpointer mark)
{
static bool init = false;
static IplImage *frame;
GstBuffer* buf;
Mark* mk = (Mark*) mark;
if(!init)
{
init = true;
frame = cvCreateImage(cvSize(mk->frame_w,mk->frame_h),IPL_DEPTH_8U,1);
}
buf = gst_app_sink_pull_buffer(fks);
frame->imageData = (char*)GST_BUFFER_DATA(buf);
ProcessFrame(frame);
gst_buffer_unref(buf);
return true;
}
这个工作.
PS.有很多关于这种方法的信息,但是我花了很多时间来搜索它.所以我决定在这里发布,以便至少提供一些搜索关键字.
UPDATE.
还有更多关于连接gstreamer和opencv的信息.这是关于将缓冲区转换为iplimage.
首先,我们需要接收rgb缓冲区,使转换尽可能简单.为了做到这一点,我们将用appsink替换appink,连接到ffmpegcolorspace
cout<<"Creating appsink"<<endl;
appsink = gst_element_factory_make("appsink",1);
csp = gst_element_factory_make("ffmpegcolorspace","csp");
sinkpipe = gst_pipeline_new("sinkp");
gst_bin_add_many(GST_BIN(sinkpipe),csp,NULL);
gst_element_link_filtered(csp,gst_caps_new_simple("video/x-raw-rgb",NULL));
pad = gst_element_get_static_pad(csp,"sink");
gst_element_add_pad(sinkpipe,gst_ghost_pad_new("ghost",pad));
g_object_unref(pad);
//...
g_object_set(G_OBJECT(playbin),sinkpipe,NULL);
//...
g_signal_connect(appsink,G_CALLBACK(GetFrame),(gpointer) mark);
//...
//caps_struct can be retrieved via writing data probe
//search for it in streamer manual
cout<<"Getting frame resolution"<<endl;
gst_structure_get_int(caps_struct,"width",&(mark->frame_w));
gst_structure_get_int(caps_struct,"height",&(mark->frame_h));
gst_structure_get_int(caps_struct,"depth",&depth);
mark->GeneratePoints();
frame = cvCreateImage(cvSize(mark->frame_w,mark->frame_h),depth/3,3);
//callback function
gboolean Core::GetFrame(GstAppSink *fks,gpointer frame)
{
IplImage* frame_temp = frame
IplImage* frame_temp_two = cvCloneImage(frame_temp);
GstBuffer* buf;
buf = gst_app_sink_pull_buffer(fks);
frame_temp_two->imageData = (char*) GST_BUFFER_DATA(buf);
cvConvertImage(frame_temp_two,frame_temp,CV_CVTIMG_SWAP_RB);
ProcessFrame(frame_temp);
gst_buffer_unref(buf);
return true;
}
我希望这将有助于某人.
