How to create OpenCV cv::Mat from NvBuffer in Jetpack 5.1

Robotics & Edge Computing Jetson & Embedded Systems Jetson Orin Nano
, ,
8

Hi,

In case you still need it, check this patch:

diff --git a/multimedia_api/ll_samples/samples/13_argus_multi_camera/main.cpp b/multimedia_api/ll_samples/samples/13_argus_multi_camera/main.cpp
index 1bd8ed9..2e83025 100644
--- a/multimedia_api/ll_samples/samples/13_argus_multi_camera/main.cpp
+++ b/multimedia_api/ll_samples/samples/13_argus_multi_camera/main.cpp
@@ -39,6 +39,8 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+#include <opencv2/opencv.hpp>
+
 using namespace Argus;
 using namespace EGLStream;
 
@@ -267,7 +269,8 @@ bool ConsumerThread::threadInitialize()
     /* Allocate composited buffer */
     input_params.width = STREAM_SIZE.width();
     input_params.height = STREAM_SIZE.height();
-    input_params.colorFormat = NVBUF_COLOR_FORMAT_NV12;
+    input_params.colorFormat = NVBUF_COLOR_FORMAT_RGBA;
     input_params.layout = NVBUF_LAYOUT_PITCH;
     input_params.memType = NVBUF_MEM_SURFACE_ARRAY;
     input_params.memtag = NvBufSurfaceTag_VIDEO_CONVERT;
@@ -356,8 +359,8 @@ bool ConsumerThread::threadExecute()
             {
                 batch_surf[i] = NULL;
                 m_dmabufs[i] = iNativeBuffer->createNvBuffer(iEglOutputStreams[i]->getResolution(),
-                                                          NVBUF_COLOR_FORMAT_YUV420,
-                                                          NVBUF_LAYOUT_BLOCK_LINEAR);
+                                                          NVBUF_COLOR_FORMAT_RGBA,
+                                                          NVBUF_LAYOUT_PITCH);
                 if (!m_dmabufs[i])
                     CONSUMER_PRINT("\tFailed to create NvBuffer\n");
                 if (-1 == NvBufSurfaceFromFd(m_dmabufs[i], (void**)(&batch_surf[i])))
@@ -374,7 +377,19 @@ bool ConsumerThread::threadExecute()
         {
             /* Composite multiple input to one frame */
             NvBufSurfTransformMultiInputBufCompositeBlend(batch_surf, pdstSurf, &m_compositeParam);
-            g_renderer->render(m_compositedFrame);
+            NvBufSurfaceMap(pdstSurf, -1, 0, NVBUF_MAP_READ);
+            NvBufSurfaceSyncForCpu(pdstSurf, -1, 0);
+
+            cv::Mat imgbuf = cv::Mat(STREAM_SIZE.height(),
+                                     STREAM_SIZE.width(),
+                                     CV_8UC4, pdstSurf->surfaceList->mappedAddr.addr[0]);
+            cv::Mat display_img;
+            cvtColor(imgbuf, display_img, cv::COLOR_RGBA2BGR);
+            
+            NvBufSurfaceUnMap(pdstSurf, -1, 0);
+
+            cv::imshow("img", display_img);
+            cv::waitKey(1);
         }
         else
             g_renderer->render(m_dmabufs[0]);

You also need to use opencv4 instead of opencv in Makefile:

+CPPFLAGS+=`pkg-config --cflags opencv4`
+LDFLAGS+=`pkg-config --libs opencv4`
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