Conversion of cv::Mat to GstBuffer
Michael Gruner
michael.gruner at ridgerun.com
Thu Mar 14 21:21:52 UTC 2019
Can you run your app with warning logging enabled? Any of the following should work:
./app --gst-debug=2
Or
GST_DEBUG=2 ./app
> On Mar 14, 2019, at 2:17 PM, Saurabh Bora <saurabh9bora at gmail.com> wrote:
>
> Hi Experts!,
>
> Thanks!! Michael, I tried the approach suggested by you and it works fine. I could verify the conversion of cv::Mat to GstBuffer and vice versa. On cv::write I get exact image that I had copied to GstBuffer.
>
> However, I am unable to get correct image on autovidesink. With current code below, I see a skewed and distorted grayscale image. Note that I had to set width and height of videocaps on appsrc element as 133, 133 respectively, even though dimesnions of my input image is 134*134. If I set width and height as 134, 134 in videocaps, I see a black videosink.
>
> //----------------------------------------------------------
> #include <gst/gst.h>
> #include <opencv2/opencv.hpp>
> #include <opencv2/highgui.hpp>
>
> static GMainLoop *loop;
>
> void buffer_destroy(gpointer data)
> {
> cv::Mat* done = (cv::Mat*)data;
> delete done;
> }
>
> static void
> cb_need_data(GstElement *appsrc,
> guint unused_size,
> gpointer user_data)
> {
> static GstClockTime timestamp = 0;
> GstBuffer *buffer;
> GstFlowReturn ret;
> char *data1;
> GstMapInfo map;
>
> cv::Mat* img = new cv::Mat(cv::imread("C:/Users/212730892.LOGON/Desktop/lena.jpg"));
>
> std::cout << "cb_need_data called" << std::endl;
>
> gsize sizeInBytes = img->total() * img->elemSize();
> std::cout << "Size getting copied: " << sizeInBytes << std::endl;
> buffer = gst_buffer_new_wrapped_full((GstMemoryFlags)0, (gpointer)(img->data), sizeInBytes, 0, sizeInBytes, (gpointer)img, (GDestroyNotify)buffer_destroy);
>
> gsize bufferSize = gst_buffer_get_size(buffer);
> std::cout << "Buffer Size: " << bufferSize << std::endl;
>
> //Convert GstBuffer back to cv::Mat, to check if data was correctly copied
> GstMapInfo info;
> gst_buffer_map(buffer, &info, GST_MAP_READ);
> cv::Mat img2(cv::Size(img->size().height, img->size().width), CV_8UC3, (char*)(info.data));
> cv::imwrite("C:/Users/212730892.LOGON/Desktop/dummy1.jpg", img2);
>
> GST_BUFFER_OFFSET(buffer) = 0;
> GST_BUFFER_PTS(buffer) = timestamp;
> GST_BUFFER_DURATION(buffer) = gst_util_uint64_scale_int(1, GST_SECOND, 30);
> //GST_BUFFER_DURATION(buffer) = GST_CLOCK_TIME_NONE;
>
> 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("autovideosink", "videosink");
>
> /* setup */
> g_object_set(G_OBJECT(appsrc), "caps",
> gst_caps_new_simple("video/x-raw",
> "format", G_TYPE_STRING, "RGB",
> "width", G_TYPE_INT, 133,
> "height", G_TYPE_INT, 133,
> "framerate", GST_TYPE_FRACTION, 1, 30,
> 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);
>
> if (gst_element_set_state(pipeline, GST_STATE_NULL) == GST_STATE_CHANGE_FAILURE)
> {
> g_printerr("Unable to set the pipeline to the playing state.\n");
> }
>
> // Free resources
> gst_object_unref(GST_OBJECT(pipeline));
> g_main_loop_unref(loop);
>
> return 0;
> }
> //-------------------------------------------------------------------------
>
> I am new to gstreamer framework and it would be a great help if someone could point me in right direction.
>
> Thanks and Regards,
> Saurabh Bora
>
>
> On Wed, Mar 13, 2019 at 11:48 PM Michael Gruner <michael.gruner at ridgerun.com <mailto:michael.gruner at ridgerun.com>> wrote:
> It looks like img2, being a local variable, ends its life when “cb_need_data” ends. That leaves the pointer in “buffer” invalid. For this one you’re better off with the copy.
>
> Another option is to alloc img2 on the heap, and use gst_buffer_new_wrapped_full to carry img2 along with buffer and free then together.
>
> Michael
> www.ridgerun.com <http://www.ridgerun.com/>
>
> On Mar 13, 2019, at 10:51 AM, Saurabh Bora <saurabh9bora at gmail.com <mailto:saurabh9bora at gmail.com>> wrote:
>
>> Hi Michael,
>>
>> Thanks! for your input. I tried what you suggested as below:
>>
>> //---------------------------------------------------------------
>> #include <gst/gst.h>
>> #include <opencv2/opencv.hpp>
>> #include <opencv2/highgui.hpp>
>> #include <opencv2/imgproc/imgproc.hpp>
>>
>> static GMainLoop *loop;
>>
>> static void
>> cb_need_data(GstElement *appsrc,
>> guint unused_size,
>> gpointer user_data)
>> {
>> static GstClockTime timestamp = 0;
>> GstBuffer *buffer;
>> guint size, depth, height, width, step, channels;
>> GstFlowReturn ret;
>> guchar *data1;
>> GstMapInfo map;
>>
>> cv::Mat img2;
>> cv::Mat img = cv::imread("C:/Users/212730892.LOGON/Desktop/lena.jpg");
>> cv::cvtColor(img, img2, cv::COLOR_BGR2RGB);
>>
>> height = img.size().height;
>> width = img.size().width;
>> //step = img.widthStep;
>> channels = img.channels();
>> //depth = img->depth;
>> data1 = (guchar *)img.data;
>> size = height * width * channels * sizeof(guchar);
>>
>> std::cout << "cb_need_data called" << std::endl;
>>
>> buffer = gst_buffer_new_wrapped(img2.data, img2.total() * img2.elemSize());
>>
>> GstMapInfo info;
>> gst_buffer_map(buffer, &info, GST_MAP_READ);
>> cv::Mat mat(height, width, CV_8UC3, info.data);
>> cv::imshow("Output", mat);
>> //gst_buffer_unmap(buffer, &info);
>>
>> 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("autovideosink", "videosink");
>>
>> /* setup */
>> g_object_set(G_OBJECT(appsrc), "caps",
>> gst_caps_new_simple("video/x-raw",
>> "format", G_TYPE_STRING, "RGB",
>> "width", G_TYPE_INT, 134,
>> "height", G_TYPE_INT, 134,
>> "framerate", GST_TYPE_FRACTION, 1, 1,
>> NULL), NULL);
>> gst_bin_add_many(GST_BIN(pipeline), appsrc, conv, videosink, NULL);
>> gst_element_link_many(appsrc, conv, videosink, NULL);
>> //g_object_set (videosink, "device", "/dev/video0", 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);
>>
>> if (gst_element_set_state(pipeline, GST_STATE_NULL) == GST_STATE_CHANGE_FAILURE)
>> {
>> g_printerr("Unable to set the pipeline to the playing state.\n");
>> }
>>
>> // Free resources
>> gst_object_unref(GST_OBJECT(pipeline));
>> g_main_loop_unref(loop);
>>
>> return 0;
>> }
>> //----------------------------------------------------------------------------------------------
>>
>> It still does not work as expected. It would be a great help if you could point out where I am going wrong.
>> Thanks!!
>>
>> On Wed, Mar 13, 2019 at 7:40 PM Michael Gruner <michael.gruner at ridgerun.com <mailto:michael.gruner at ridgerun.com>> wrote:
>> Hi Saurabh
>>
>> Yo may convert from a cv::Mat to a GstBuffer without a memory copy by using gst_buffer_new_wrapped:
>>
>> https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/GstBuffer.html#gst-buffer-new-wrapped <https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/GstBuffer.html#gst-buffer-new-wrapped>
>>
>> Something like:
>> buffer = gst_buffer_new_wrapped (mat.data, mat.total()*mat.elemSize());
>>
>> In order to make a cv::Mat from a GstBuffer you first need to take the data out of the buffer.
>>
>> GstMapInfo info;
>> gst_buffer_map (buffer, &info, GST_MAP_READ); // or write
>> mat = cv::Mat(height, width, CV_8C3, map.data); // change your format accordingly
>> ...
>> gst_buffer_unmap (buffer, &info);
>>
>> Hope it helps.
>>
>> Michael
>> www.ridgerun.com <http://www.ridgerun.com/>
>>
>> On Mar 13, 2019, at 7:15 AM, Saurabh Bora <saurabh9bora at gmail.com <mailto:saurabh9bora at gmail.com>> wrote:
>>
>>> Hi Experts!!,
>>>
>>> I am trying to read opencv images locally and push them into gstreamer pipeline. I am using appsrc element with "need-data" signal attached to call-back function.
>>> Please look at the code below.
>>>
>>> //------------------------------------------------------------------------------------------------------
>>> #include <gst/gst.h>
>>> #include <opencv2/opencv.hpp>
>>> #include <opencv2/highgui.hpp>
>>>
>>> static GMainLoop *loop;
>>>
>>> static void
>>> cb_need_data(GstElement *appsrc,
>>> guint unused_size,
>>> gpointer user_data)
>>> {
>>> static GstClockTime timestamp = 0;
>>> GstBuffer *buffer;
>>> guint size, depth, height, width, step, channels;
>>> GstFlowReturn ret;
>>> guchar *data1;
>>> GstMapInfo map;
>>>
>>> cv::Mat img = cv::imread("C:/Users/212730892.LOGON/Desktop/lena.jpg");
>>> height = img.size().height;
>>> width = img.size().width;
>>> //step = img.widthStep;
>>> channels = img.channels();
>>> //depth = img->depth;
>>> data1 = (guchar *)img.data;
>>> size = height * width* channels;
>>>
>>> // Copy cv::Mat to GstBuffer
>>> buffer = gst_buffer_new_allocate(NULL, size, NULL);
>>> gst_buffer_map(buffer, &map, GST_MAP_WRITE);
>>> memcpy((guchar *)map.data, data1, gst_buffer_get_size(buffer));
>>>
>>> //Convert GstBuffer back to cv::Mat and write it, to check if data was correctly copied. //This is where I get to know that data is not correct.
>>> cv::Mat img2(cv::Size(134, 134), CV_8UC3, (char*)(buffer));
>>> cv::imwrite("C:/Users/212730892.LOGON/Desktop/dummy1.jpg", img2);
>>>
>>> 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("autovideosink", "videosink");
>>>
>>> /* setup */
>>> g_object_set(G_OBJECT(appsrc), "caps",
>>> gst_caps_new_simple("video/x-raw",
>>> "format", G_TYPE_STRING, "RGB",
>>> "width", G_TYPE_INT, 134,
>>> "height", G_TYPE_INT, 134,
>>> "framerate", GST_TYPE_FRACTION, 1, 1,
>>> NULL), NULL);
>>> gst_bin_add_many(GST_BIN(pipeline), appsrc, conv, videosink, NULL);
>>> gst_element_link_many(appsrc, conv, videosink, NULL);
>>> //g_object_set (videosink, "device", "/dev/video0", 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);
>>>
>>> if (gst_element_set_state(pipeline, GST_STATE_NULL) == GST_STATE_CHANGE_FAILURE)
>>> {
>>> g_printerr("Unable to set the pipeline to the playing state.\n");
>>> }
>>>
>>> // Free resources
>>> gst_object_unref(GST_OBJECT(pipeline));
>>> g_main_loop_unref(loop);
>>>
>>> return 0;
>>> }
>>> //-------------------------------------------------------------------------------------------------------------------------------------
>>>
>>> In cb_need_data, the part where copying I am copying to GstBuffer seems to be wrong and it does not work as expected.
>>> Can anyone, please help me understand, how can I copy the image data perfectly and pass it downstream to other elements without losing any data?
>>>
>>> --
>>> Thanks and Regards,
>>> Saurabh Bora
>>>
>>> PH NO : 7038166900
>>> EMAIL : saurabh9bora at gmail.com <mailto:saurabh9bora at gmail.com>
>>> saurabh9bora at outlook.com <mailto:saurabh9bora at outlook.com>_______________________________________________
>>> gstreamer-devel mailing list
>>> gstreamer-devel at lists.freedesktop.org <mailto:gstreamer-devel at lists.freedesktop.org>
>>> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel <https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel>_______________________________________________
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>> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel <https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel>
>>
>> --
>> Thanks and Regards,
>> Saurabh Bora
>>
>> PH NO : 7038166900
>> EMAIL : saurabh9bora at gmail.com <mailto:saurabh9bora at gmail.com>
>> saurabh9bora at outlook.com <mailto:saurabh9bora at outlook.com>_______________________________________________
>> gstreamer-devel mailing list
>> gstreamer-devel at lists.freedesktop.org <mailto:gstreamer-devel at lists.freedesktop.org>
>> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel <https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel>_______________________________________________
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> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel <https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel>
>
> --
> Thanks and Regards,
> Saurabh Bora
>
> PH NO : 7038166900
> EMAIL : saurabh9bora at gmail.com <mailto:saurabh9bora at gmail.com>
> saurabh9bora at outlook.com <mailto:saurabh9bora at outlook.com>_______________________________________________
> gstreamer-devel mailing list
> gstreamer-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
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