Chief Delphi - Network Tables

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- Programming (http://www.chiefdelphi.com/forums/forumdisplay.php?f=51)

- - Network Tables (http://www.chiefdelphi.com/forums/showthread.php?t=128328)

lucas.alvarez96

29-03-2014 18:13

Network Tables

Yeah, I know everybody has asked for this before, but I really need a Network Tables library for C++. I'd used pynetworktables and had a fully functioning code with Python, but the latency while using an Axis IP cam (even while connected to my laptop's ethernet port) is too dang high! When I tried C++, it worked like a charm, but there's no network table implementation for sending simple values such as x and y coordinates. Network sockets are sort of intimidating, and I haven't the faintest on how to implement them on our DS (with C++ and the openCV library) and the robot (using java). I would be truly grateful if someone could send me a part of their sockets code, just to get an idea on how to code it.
Thanks in advance! :D

virtuald

30-03-2014 10:22

Re: Network Tables

How high is the latency? We haven't had any significant problems with it, and all of our code is implemented in python (robot + image processing + custom dashboard).

lucas.alvarez96

30-03-2014 15:56

Re: Network Tables

I'd reckon like 3 seconds of latency...my FPS is great, it's just that there has to be some problems with the buffer :(

Code:

import cv2

import urllib 

import numpy as np



stream=urllib.urlopen('http://10.25.76.11/mjpg/video.mjpg')

bytes=''

while True:

    bytes+=stream.read(16384)

    a = bytes.find('\xff\xd8')

    b = bytes.find('\xff\xd9')

    if a!=-1 and b!=-1:

        jpg = bytes[a:b+2]

        bytes= bytes[b+2:]

        i = cv2.imdecode(np.fromstring(jpg, dtype=np.uint8),cv2.CV_LOAD_IMAGE_COLOR)

        cv2.imshow('i',i)

        if cv2.waitKey(1) ==27:

            exit(0)

I got the code from StackOverflow. I had tried using a simple VideoCapture(ip), and got it to work on C++, but Python just throws up some errors:

Code:

Traceback (most recent call last):

  File "C:\Users\Lucas\Documents\opencv\opencv\webcam.py", line 7, in <module>

    cv2.imshow("window", img)

error: C:\slave\WinInstallerMegaPack\src\opencv\modules\core\src\array.cpp:2482: error: (-206) Unrecognized or unsupported array type

And when I print out the value of "ret" (the first variable outputted by VideoCapture::read()), I get False, which indicates that there is no image being captured (duh).

Any ideas?

virtuald

30-03-2014 16:06

Re: Network Tables

I use this:

Code:

        vc = cv2.VideoCapture()

        vc.set(cv2.cv.CV_CAP_PROP_FPS, 1)

        

        if not vc.open('http://%s/mjpg/video.mjpg' % self.camera_ip):

            return



        while True:

            retval, img = vc.read(buffer)

            ...

One bug present in OpenCV that hasn't been fixed can be found on their bug tracker here: http://code.opencv.org/issues/2877 . If you compile your own OpenCV you can patch the bug. I've been meaning to patch it in a better way but haven't done so yet, as I don't have an axis camera easily available for testing.

lucas.alvarez96

30-03-2014 16:31

Re: Network Tables

Ok so I tried this:

Code:

import cv2

import numpy as np

import time



camera_ip = "10.25.76.11"



vc = cv2.VideoCapture()

vc.set(cv2.cv.CV_CAP_PROP_FPS, 1)

        

if not vc.open('http://%s/mjpg/video.mjpg' % camera_ip):

    time.sleep(0)



while True:

    retval, img = vc.read(buffer)

    cv2.imshow("img", img)

    if cv2.waitKey(20) == 27:

        break



cv2.destroyAllWindows()

exit(0)

And got this:

Code:

Traceback (most recent call last):

  File "C:/Users/Lucas/Desktop/cdch/render_stream3.py", line 14, in <module>

    retval, img = vc.read(buffer)

TypeError: <unknown> is not a numpy array

So truth be told, I'm not quite sure what's going on... :confused:

And yeah, I'd read somewhere that ffmpeg could sometimes be the source of the problem, but I'm on windows and haven't the faintest idea on how to compile from source...

I'm very sorry Dustin if the problem is to obvious, but I've been struggling with this for weeks and my team REALLY needs it for the championships...

virtuald

30-03-2014 16:35

Re: Network Tables

Sorry, I copy/pasted that incorrectly. You should remove the buffer from the vc.read() call for initial testing. buffer happens to be a python keyword, and I was using it as a variable, so I wasn't allocating a new image buffer each time. So it was actually something like...

Code:



            h = vc.get(cv2.cv.CV_CAP_PROP_FRAME_WIDTH)

            w = vc.get(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT)

            

            capture_buffer = np.empty(shape=(h, w, 3), dtype=np.uint8)



            while True:

                retval, img = vc.read(capture_buffer)

lucas.alvarez96

30-03-2014 17:03

Re: Network Tables

Yeaaaaah.....same error....

Code:

Traceback (most recent call last):

  File "C:\Users\Lucas\Desktop\cdch\render_stream3.py", line 19, in <module>

    cv2.imshow("img", img)

error: C:\slave\WinInstallerMegaPack\src\opencv\modules\core\src\array.cpp:2482: error: (-206) Unrecognized or unsupported array type

Using this code:

Code:

import cv2

import numpy as np

import time



camera_ip = "10.25.76.11"



vc = cv2.VideoCapture()

vc.set(cv2.cv.CV_CAP_PROP_FPS, 1)

        

if not vc.open('http://%s/mjpg/video.mjpg' % camera_ip):

    time.sleep(0)



h = vc.get(cv2.cv.CV_CAP_PROP_FRAME_WIDTH)

w = vc.get(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT)

capture_buffer = np.empty(shape=(h, w, 3), dtype=np.uint8)



while True:

    retval, img = vc.read(capture_buffer)

    cv2.imshow("img", img)

    if cv2.waitKey(20) == 27:

        break



cv2.destroyAllWindows()

exit(0)

virtuald

30-03-2014 17:06

Re: Network Tables

Interesting. Don't pass it a capture buffer then, and see what happens.

virtuald

30-03-2014 17:07

Re: Network Tables

Wait, the error is on the imshow. Odd. What type/shape is the image?

Code:

print img

print img.shape

print img.type

lucas.alvarez96

30-03-2014 17:18

Re: Network Tables

With or without buffer, there's a problem with the capture. retval returns false, and the img array returns None, so I can't print img.shape or img.type.

Code:

AttributeError: 'NoneType' object has no attribute 'shape'

virtuald

31-03-2014 19:14

Re: Network Tables

Quote:

Originally Posted by lucas.alvarez96 (Post 1366746)

With or without buffer, there's a problem with the capture. retval returns false, and the img array returns None, so I can't print img.shape or img.type.

Code:

AttributeError: 'NoneType' object has no attribute 'shape'

Odd. That's very strange. Must be something with the way your ffmpeg is compiled.

lucas.alvarez96

31-03-2014 19:34

Re: Network Tables

Well, if Windows 8.1 or OpenCV doesn't include ffmpeg by default, then I should go and install it....

virtuald

31-03-2014 20:13

Re: Network Tables

Oh that's right! You have to copy the ffmpeg DLL to C:\Python27 for it to work correctly. It should be included with the opencv binary distribution. It's rather odd to me that they're separate. It'll be called something like 'opencv_ffmpeg2xx.dll'

JamesTerm

31-03-2014 20:14

Re: Network Tables

Quote:

Originally Posted by lucas.alvarez96 (Post 1366349)

Did you try SmartCppDashboard? Its in first forge with full source to network tables using winsock2. It also uses ffmpeg to support h264 a special build to minimize latency for it... I can get link later once I get to a PC.

lucas.alvarez96

31-03-2014 22:50

Re: Network Tables

Quote:

Ok Dustin, so I copied the .dll and discovered that I had an old .dll in there (246. I'm using 248). So it's still not working, but I did discover in the source folder that there's an ffmpeg folder in the 3rdparty folder which include a make file and dll files. So I'm gonna give that a try.

Quote:

James, that would be awesome! Please post the link as soon as you can. Thanks man!

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