Jetson | Technology Tutorials

In this lesson we learn how to use Python Classes, Methods and Threading to run two cameras in OpenCV without latency or synchronization problems. Below we include the code developed in the video above.

from threading import Thread
import cv2
import time
import numpy as np

class vStream:
    def __init__(self,src,width,height):
        self.width=width
        self.height=height
        self.capture=cv2.VideoCapture(src)
        self.thread=Thread(target=self.update,args=())
        self.thread.daemon=True
        self.thread.start()
    def update(self):
        while True:
            _,self.frame=self.capture.read()
            self.frame2=cv2.resize(self.frame,(self.width,self.height))
    def getFrame(self):
        return self.frame2
flip=2
dispW=640
dispH=480
camSet='nvarguscamerasrc !  video/x-raw(memory:NVMM), width=3264, height=2464, format=NV12, framerate=21/1 ! nvvidconv flip-method='+str(flip)+' ! video/x-raw, width='+str(dispW)+', height='+str(dispH)+', format=BGRx ! videoconvert ! video/x-raw, format=BGR ! appsink'
cam1=vStream(1,dispW,dispH)
cam2=vStream(camSet,dispW,dispH)
font=cv2.FONT_HERSHEY_SIMPLEX
startTime=time.time()
dtav=0
while True:
    try:
        myFrame1=cam1.getFrame()
        myFrame2=cam2.getFrame()
        myFrame3=np.hstack((myFrame1,myFrame2))
        dt=time.time()-startTime
        startTime=time.time()
        dtav=.9*dtav+.1*dt
        fps=1/dtav
        cv2.rectangle(myFrame3,(0,0),(140,40),(0,0,255),-1)
        cv2.putText(myFrame3,str(round(fps,1))+' fps',(0,25),font,.75,(0,255,255),2)
        cv2.imshow('ComboCam',myFrame3)
        cv2.moveWindow('ComboCam',0,0)



    except:
        print('frame not available')
        
    if cv2.waitKey(1)==ord('q'):
        cam1.capture.release()
        cam2.capture.release()
        cv2.destroyAllWindows()
        exit(1)
        break

from threading import Thread

import cv2

import time

import numpy as np

class vStream:

def __init__(self,src,width,height):

self.width=width

self.height=height

self.capture=cv2.VideoCapture(src)

self.thread=Thread(target=self.update,args=())

self.thread.daemon=True

self.thread.start()

def update(self):

while True:

_,self.frame=self.capture.read()

self.frame2=cv2.resize(self.frame,(self.width,self.height))

def getFrame(self):

return self.frame2

flip=2

dispW=640

dispH=480

camSet='nvarguscamerasrc ! video/x-raw(memory:NVMM), width=3264, height=2464, format=NV12, framerate=21/1 ! nvvidconv flip-method='+str(flip)+' ! video/x-raw, width='+str(dispW)+', height='+str(dispH)+', format=BGRx ! videoconvert ! video/x-raw, format=BGR ! appsink'

cam1=vStream(1,dispW,dispH)

cam2=vStream(camSet,dispW,dispH)

font=cv2.FONT_HERSHEY_SIMPLEX

startTime=time.time()

dtav=0

while True:

try:

myFrame1=cam1.getFrame()

myFrame2=cam2.getFrame()

myFrame3=np.hstack((myFrame1,myFrame2))

dt=time.time()-startTime

startTime=time.time()

dtav=.9*dtav+.1*dt

fps=1/dtav

cv2.rectangle(myFrame3,(0,0),(140,40),(0,0,255),-1)

cv2.putText(myFrame3,str(round(fps,1))+' fps',(0,25),font,.75,(0,255,255),2)

cv2.imshow('ComboCam',myFrame3)

cv2.moveWindow('ComboCam',0,0)

except:

print('frame not available')

if cv2.waitKey(1)==ord('q'):

cam1.capture.release()

cam2.capture.release()

cv2.destroyAllWindows()

exit(1)

break

In this lesson we show you how to understand the great mystery known as Gstreamer. Most folks using the NVIDIA Jetson Nano or the NVIDIA Jetson Exavier NX just copy and past the launch string they found on the internet, but do not have a clue how Gstreamer actually works. In this video we will take you through it step-by-step, and show you how to actually understand what you are doing, and how to design your own pipes for maximum performance and image quality. Below are all the commands we used in the video lesson

gst-launch-1.0 audiotestsrc ! alsasink

gst-inspect-1.0 audiotestsrc

gst-launch-1.0 audiotestsrc freq=500 ! alsasink

gst-launch-1.0 audiotestsrc freq=500 ! alsasink

gst-inspect-1.0 audiotestsrc

gst-launch-1.0 audiotestsrc freq=500 ! audio/x-raw, format=U8 ! alsasink

gst-launch-1.0 audiotestsrc freq=500 ! audio/x-raw, format=U18LE ! alsasink

gst-launch-1.0 audiotestsrc freq=500 ! audio/x-raw, format=U18LE ! audioconvert ! audio/x-raw, format=U8 ! alsasink

gst-launch-1.0 videotestsrc ! ximagesink

gst-inspect-1.0 videotestsrc

gst-launch-1.0 videotestsrc pattern=11 ! ximagesink

gst-launch-1.0 videotestsrc pattern=0 ! video/x-raw, format=BGR ! ximagesink

gst-inspect-1.0 autovideoconvert

gst-launch-1.0 videotestsrc pattern=0 ! video/x-raw, format=BGR ! autovideoconvert ! ximagesink

gst-launch-1.0 videotestsrc pattern=0 ! video/x-raw, format=BGR ! autovideoconvert ! videoconvert ! video/x-raw, width=1280, height=960 !  ximagesink 

gst-launch-1.0 videotestsrc pattern=0 ! video/x-raw, format=BGR ! autovideoconvert ! videoconvert ! video/x-raw, width=1280, height=960, framerate=30/1 !  ximagesink

gst-launch-1.0 videotestsrc pattern=0 ! video/x-raw, format=BGR ! autovideoconvert ! videoconvert ! video/x-raw, width=1280, height=960, framerate=1/1 !  ximagesink

gst-launch-1.0 nvarguscamerasrc ! autovideo

gst-launch-1.0 nvarguscamerasrc !  nvvidconv flip-method=2 ! video/x-raw,width=1280,height=840 ! autovideoconvert  !  ximagesink

gst-launch-1.0 nvarguscamerasrc ! "video/x-raw(memory:NVMM),width=3264,height=2464,format=NV12,framerate=21/1" !  nvvidconv flip-method=2 ! video/x-raw,width=640,height=480 ! autovideoconvert  !  ximagesink

gst-launch-1.0 nvarguscamerasrc ! "video/x-raw(memory:NVMM),width=3264,height=2464,format=NV12,framerate=21/1" !  nvvidconv flip-method=2 ! video/x-raw,width=640,height=480 ! autovideoconvert  ! agingtv ! ximagesink

gst-launch-1.0 nvarguscamerasrc ! "video/x-raw(memory:NVMM),width=3264,height=2464,format=NV12,framerate=21/1" !  nvvidconv flip-method=2 ! video/x-raw,width=640,height=480 ! autovideoconvert  ! agingtv ! ximagesink


gst-launch-1.0 nvarguscamerasrc ! "video/x-raw(memory:NVMM),width=3264,height=2464,format=NV12,framerate=21/1" !  nvvidconv flip-method=2 ! video/x-raw,width=1280,height=960 ! autovideoconvert  ! agingtv ! coloreffects preset=sepia ! ximagesink

gst-launch-1.0  v4l2src device=/dev/video1 ! xvimagesink

gst-launch-1.0  v4l2src device=/dev/video1 ! video/x-raw,framerate=20/1,width=864,height=480 ! xvimagesink

gst-launch-1.0 audiotestsrc ! alsasink

gst-inspect-1.0 audiotestsrc

gst-launch-1.0 audiotestsrc freq=500 ! alsasink

gst-inspect-1.0 audiotestsrc

gst-launch-1.0 audiotestsrc freq=500 ! audio/x-raw, format=U8 ! alsasink

gst-launch-1.0 audiotestsrc freq=500 ! audio/x-raw, format=U18LE ! alsasink

gst-launch-1.0 audiotestsrc freq=500 ! audio/x-raw, format=U18LE ! audioconvert ! audio/x-raw, format=U8 ! alsasink

gst-launch-1.0 videotestsrc ! ximagesink

gst-inspect-1.0 videotestsrc

gst-launch-1.0 videotestsrc pattern=11 ! ximagesink

gst-launch-1.0 videotestsrc pattern=0 ! video/x-raw, format=BGR ! ximagesink

gst-inspect-1.0 autovideoconvert

gst-launch-1.0 videotestsrc pattern=0 ! video/x-raw, format=BGR ! autovideoconvert ! ximagesink

gst-launch-1.0 videotestsrc pattern=0 ! video/x-raw, format=BGR ! autovideoconvert ! videoconvert ! video/x-raw, width=1280, height=960 ! ximagesink

gst-launch-1.0 videotestsrc pattern=0 ! video/x-raw, format=BGR ! autovideoconvert ! videoconvert ! video/x-raw, width=1280, height=960, framerate=30/1 ! ximagesink

gst-launch-1.0 videotestsrc pattern=0 ! video/x-raw, format=BGR ! autovideoconvert ! videoconvert ! video/x-raw, width=1280, height=960, framerate=1/1 ! ximagesink

gst-launch-1.0 nvarguscamerasrc ! autovideo

gst-launch-1.0 nvarguscamerasrc ! nvvidconv flip-method=2 ! video/x-raw,width=1280,height=840 ! autovideoconvert ! ximagesink

gst-launch-1.0 nvarguscamerasrc ! "video/x-raw(memory:NVMM),width=3264,height=2464,format=NV12,framerate=21/1" ! nvvidconv flip-method=2 ! video/x-raw,width=640,height=480 ! autovideoconvert ! ximagesink

gst-launch-1.0 nvarguscamerasrc ! "video/x-raw(memory:NVMM),width=3264,height=2464,format=NV12,framerate=21/1" ! nvvidconv flip-method=2 ! video/x-raw,width=1280,height=960 ! autovideoconvert ! agingtv ! coloreffects preset=sepia ! ximagesink

gst-launch-1.0 v4l2src device=/dev/video1 ! xvimagesink

gst-launch-1.0 v4l2src device=/dev/video1 ! video/x-raw,framerate=20/1,width=864,height=480 ! xvimagesink

Making The World a Better Place One High Tech Project at a Time. Enjoy!

Technology Tutorials

Tag Archives: Jetson

AI on the Jetson Nano Lesson 46: Synchronizing Multiple Cameras with OpenCV

Jetson Xavier NX Lesson 4: Understanding and Using Gstreamer for Absolute Beginners

Making The World a Better Place One High Tech Project at a Time. Enjoy!