Invalid UTF-8 string. FRC Vision Processing

Team7433 · January 24, 2019, 5:17am

Hello, I am receiving this error while running my vision processing program inspired by ChickenVision, I have made many modifications and all seems to have worked and all of a sudden I can no longer run my program and I am getting this error “Received an invalid UTF-8 string: b’PE\x8e\x01and_N3frc7CommandE’”. If you have any idea what this means or require me to post anything additional that would be greatly appreciated.

auscompgeek · January 24, 2019, 5:21am

That is a warning, not an error. This would not be the cause of your vision processing breaking (unless your vision processing actually uses that string).

From the sounds of things, your robot code is sending a string over NetworkTables that appears to be gibberish. Do you have your source code available anywhere that we could investigate? (If not, what language is your robot code in?)

Team7433 · January 24, 2019, 5:35am

I have just uploaded our main file to GitHub where I am getting the error.
Link: https://github.com/DisplayedAim/IonaVision

auscompgeek · January 24, 2019, 5:40am

You have an infinite loop here:

github.com

DisplayedAim/IonaVision/blob/31ae56e60fc1331c4612680cab55614150473700/uploaded.py#L516


cameraServer = streams[0]
# Get a CvSink. This will capture images from the camera
cvSink = cameraServer.getVideo()


# (optional) Setup a CvSource. This will send images back to the Dashboard
outputStream = cameraServer.putVideo("stream", image_width, image_height)
# Allocating new images is very expensive, always try to preallocate
img = np.zeros(shape=(image_height, image_width, 3), dtype=np.uint8)


# loop forever
while True:
    # Tell the CvSink to grab a frame from the camera and put it
    # in the source image.  If there is an error notify the output.
    timestamp, img = cvSink.grabFrame(img)
    frame = img
    #frame = flipImage(img)
    if timestamp == 0:
        # Send the output the error.
        outputStream.notifyError(cvSink.getError());
        # skip the rest of the current iteration
        continue

… where you grab a frame from the camera, and then proceed to do nothing with it.

Team7433 · January 24, 2019, 5:43am

I do use it from lines 530 - 541

auscompgeek · January 24, 2019, 5:43am

Those lines are never reached due to the infinite loop directly before.

Team7433 · January 24, 2019, 5:45am

OHHH! I didn’t realise they weren’t in the loop.

Team7433 · January 24, 2019, 5:46am

Thanks a lot for your help.

auscompgeek · January 24, 2019, 5:46am

No worries. Good luck, and see you at the regionals!

I would still love to figure out why your robot code is sending gibberish over NetworkTables though…

Joe_Ross · January 24, 2019, 5:47am

What camera? It may be a known issue. See https://github.com/robotpy/robotpy-cscore/issues/58

auscompgeek · January 24, 2019, 5:49am

That’s a completely different issue. This thread is related to this one:

Team7433 · January 24, 2019, 11:54pm

I’ve had a look at outline viewer and I’m getting this spam, I’ve tried deleting that and it won’t let me :?

virtuald · January 25, 2019, 12:37am

The last time I saw gibberish like that was from a C++ team that improperly initialized a command with a temporary string instead of a ‘real’ string. Are you using C++ for your robot code?

Team7433 · January 25, 2019, 12:43am

Yes sir.

virtuald · January 25, 2019, 4:23am

Well. You’re doing something weird when initializing one of your commands.

If you can point me at your code (or send it to me), I can take a look and tell you what’s wrong.