Conversion of cv::Mat to GstBuffer
Saurabh Bora
saurabh9bora at gmail.com
Thu Mar 14 20:17:49 UTC 2019
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>
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
>
> On Mar 13, 2019, at 10:51 AM, Saurabh Bora <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> 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
>>
>> 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
>>
>> On Mar 13, 2019, at 7:15 AM, Saurabh Bora <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
>> saurabh9bora at outlook.com
>>
>> _______________________________________________
>> gstreamer-devel mailing list
>> gstreamer-devel at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>>
>> _______________________________________________
>> gstreamer-devel mailing list
>> gstreamer-devel at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>
>
>
> --
> Thanks and Regards,
> Saurabh Bora
>
> PH NO : 7038166900
> EMAIL : saurabh9bora at gmail.com
> saurabh9bora at outlook.com
>
> _______________________________________________
> gstreamer-devel mailing list
> gstreamer-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>
> _______________________________________________
> gstreamer-devel mailing list
> gstreamer-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
--
Thanks and Regards,
Saurabh Bora
PH NO : 7038166900
EMAIL : saurabh9bora at gmail.com
saurabh9bora at outlook.com
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