How to receive images from Jetson TX1 embedded camera?

I flashed my Jetson TX1 with the latest Jetpack (Linux For Tegra R23.2), and the following command works perfectly:

gst-launch-1.0 nvcamerasrc fpsRange="30.0 30.0" ! 'video/x-raw(memory:NVMM), width=(int)1920, height=(int)1080, format=(string)I420, framerate=(fraction)30/1' ! nvtee ! nvvidconv flip-method=2 ! 'video/x-raw(memory:NVMM), format=(string)I420' ! nvoverlaysink -e

I tried to use the following python program to receive images from webcam:

source: http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_gui/py_video_display/py_video_display.html

import numpy as np
import cv2

cap = cv2.VideoCapture(0)

while(True):
    # Capture frame-by-frame
    ret, frame = cap.read()

    # Our operations on the frame come here
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

    # Display the resulting frame
    cv2.imshow('frame',gray)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()

I got the following error:

OpenCV Error: Assertion failed (scn == 3 || scn == 4) in cvtColor, file /hdd/buildbot/slave_jetson_tx_2/35-O4T-L4T-Jetson-L/opencv/modules/imgproc/src/color.cpp, line 3739
Traceback (most recent call last):
  File "webcam.py", line 11, in <module>
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
cv2.error: /hdd/buildbot/slave_jetson_tx_2/35-O4T-L4T-Jetson-L/opencv/modules/imgproc/src/color.cpp:3739: error: (-215) scn == 3 || scn == 4 in function cvtColor

I know the problem is that it cannot receive images from webcam. I also changed the code to just show the received image from webcam, but it gives me error that means no image it get from camera.

I also tried to use C++ with the following code:

#include "opencv2/opencv.hpp"
using namespace cv;
int main(int argc, char** argv)
{
    VideoCapture cap;
    // open the default camera, use something different from 0 otherwise;
    // Check VideoCapture documentation.
    if(!cap.open(0))
        return 0;
    for(;;)
    {
          Mat frame;
          cap >> frame;
          if( frame.empty() ) break; // end of video stream
          imshow("this is you, smile! :)", frame);
          if( waitKey(1) == 27 ) break; // stop capturing by pressing ESC 
    }
    // the camera will be closed automatically upon exit
    // cap.close();
    return 0;
}

and it compiled without any errors using

g++ webcam.cpp -o webcam `pkg-config --cflags --libs opencv`

But again, when I'm running the program I receive this error:

$ ./webcam
Unable to stop the stream.: Device or resource busy
Unable to stop the stream.: Bad file descriptor
VIDIOC_STREAMON: Bad file descriptor
Unable to stop the stream.: Bad file descriptor

What I've missed? Is there any command I should run to activate webcam before running this program?

Solution

According to the nvidia forums you need to get the gstreamer pipeline correct. And at the moment opencv can not autodetect the stream for the nvcamera.

The only way I got it to work, was with Opencv3 and this line of code to grab the video:

cap = cv2.VideoCapture("nvcamerasrc ! video/x-raw(memory:NVMM), width=(int)640, height=(int)480, format=(string)I420, framerate=(fraction)30/1 ! nvvidconv flip-method=2 ! video/x-raw, format=(string)I420 ! videoconvert ! video/x-raw, format=(string)BGR ! appsink")