How to use gst_memory_new_wrapped wrap opencv mat ?

[Erickson.LU]

Hi all,
    I use try to use the procedure “v4l2(V4L2_PIX_FMT_YUYV)->opencv mat->(do
something)->gstreamer”.

v4l2->gstreamer

I think the pipeline is ok, cause i have used it to show v4l2 YUY2 format.
Like v4l2 (V4L2_PIX_FMT_YUYV)

-> cv::Mat mat = cv::Mat(480,640,CV_8UC2,(void*)fbuffer1);

-> wrapped_mem1 = gst_memory_new_wrapped( (GstMemoryFlags)0, (gpointer)
fbuffer1, *len* , 0, *len* , NULL, NULL);

->
    g_object_set(G_OBJECT(gst_handle->src), "caps",
                 gst_caps_new_simple("video/x-raw",
                                     "format", G_TYPE_STRING, "YUY2",
                                     "width", G_TYPE_INT, cmdline.width,
                                     "height", G_TYPE_INT, cmdline.s_height,
                                     "framerate", GST_TYPE_FRACTION, 30, 1,
                                     NULL), NULL);

v4l2->mat->do something -> appsrc

when i try to do some thing to mat and stream it out. There is the
problem...
len=640*480*2

----------------------------------------------------------------------------------------------------------------

            memcpy(fbuffer1, (((unsigned char *) (cap_ptr[0])) ), *len*);
//fbuffer1 is the unsigned char *  reference at v4l2_capture_buffer.ptr
cv::Mat mat = cv::Mat(480,640,CV_8UC2,(void*)fbuffer1);
            cv::Mat rgb_mat;
            cv::cvtColor(mat,rgb_mat,cv::COLOR_YUV2BGR_YUY2);
//***************do
something***********************************************//
            cv::cvtColor(rgb_cv,rgb_cv,CV_BGR2YUV_I420);
            wrapped_mem1 = gst_memory_new_wrapped( (GstMemoryFlags)0,
(gpointer) rgb_cv.data, *len* , 0, *len* , NULL, NULL);
            gst_buffer_append_memory(buffer1, wrapped_mem1);
            g_signal_emit_by_name(gst_handle1->src, "push-buffer", buffer1,
&ret1);

-------------------------------------------------------------------------------------------------------------
#define PIPELINE "appsrc name=mysource !" \
        " video/x-raw,width=%d,height=%d ! "\
" videoconvert ! xvimagesink "

gst_handle->src = gst_bin_get_by_name (GST_BIN(gst_handle->pipeline),
"mysource");

    gst_handle->width  = cmdline.width;
    gst_handle->height = cmdline.height;

    g_object_set(G_OBJECT(gst_handle->src), "caps",
                 gst_caps_new_simple("video/x-raw",
                                     "format", G_TYPE_STRING, "I420",
                                     "width", G_TYPE_INT, cmdline.width,
                                     "height", G_TYPE_INT, cmdline.s_height,
                                     "framerate", GST_TYPE_FRACTION, 30, 1,
                                     NULL), NULL);

-------------------------------------------------------------------------------------------------------------
The process crash at "gst_memory_new_wrapped" so many times but some time it
will be OK.

Some things beyond the topic

If i just use the mat has been converted to BGR and stream it out. I don't
know why the xvimagesink show all GREEN.

Thank for you focus.









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[Erickson.LU]

v4l2->gstreamer
 is OK, nothing is wrong
v4l2->mat->do something -> appsrc

According to that /The process crash at "gst_memory_new_wrapped" so many
times but some time it will be OK./ .
The true is that, the process did not crash at "gst_memory_new_wrapped". It
crash at "g_signal_emit_by_name". Cause when i send the mat to appsrc
buffer. The thread own mat.data destruct himself when the function loop
again, it's a fundamental of opencv. So i forget that, when appsrc need the
buffer, it can't access it or wrong format.
Some things beyond the topic

I think the screen is GREEN as of the size of "GstMemory"  warped opencv mat
is not correct, may there is other reason for that.



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