Video-viewer does not flip camera image

Autonomous Machines Jetson & Embedded Systems Jetson Xavier NX
1

When I run video-viewer with:

video-viewer --input-width=640 --input-height=480 --input-flip=rotate-180 /dev/video0

the image does not flip. i tried two different USB cameras and other flip modes but it never does anything with the orientation of the image.

This is what it spits out before capturing:

gstCamera video options:

– URI: v4l2:///dev/video0
- protocol: v4l2
- location: /dev/video0
– deviceType: v4l2
– ioType: input
– codec: raw
– width: 640
– height: 480
– frameRate: 30.000000
– bitRate: 0
– numBuffers: 4
– zeroCopy: true
– flipMethod: rotate-180
– loop: 0
– rtspLatency 2000

[OpenGL] glDisplay – X screen 0 resolution: 1920x1080
[OpenGL] glDisplay – X window resolution: 1920x1080
[OpenGL] glDisplay – display device initialized (1920x1080)
[video] created glDisplay from display://0

glDisplay video options:

– URI: display://0
- protocol: display
- location: 0
– deviceType: display
– ioType: output
– codec: raw
– width: 1920
– height: 1080
– frameRate: 0.000000
– bitRate: 0
– numBuffers: 4
– zeroCopy: true
– flipMethod: none
– loop: 0
– rtspLatency 2000

[gstreamer] opening gstCamera for streaming, transitioning pipeline to GST_STATE_PLAYING
[gstreamer] gstreamer changed state from NULL to READY ==> mysink
[gstreamer] gstreamer changed state from NULL to READY ==> capsfilter0
[gstreamer] gstreamer changed state from NULL to READY ==> v4l2src0
[gstreamer] gstreamer changed state from NULL to READY ==> pipeline0
[gstreamer] gstreamer changed state from READY to PAUSED ==> capsfilter0
[gstreamer] gstreamer stream status CREATE ==> src
[gstreamer] gstreamer changed state from READY to PAUSED ==> v4l2src0
[gstreamer] gstreamer changed state from READY to PAUSED ==> pipeline0
[gstreamer] gstreamer stream status ENTER ==> src
[gstreamer] gstreamer message new-clock ==> pipeline0
[gstreamer] gstreamer changed state from PAUSED to PLAYING ==> capsfilter0
[gstreamer] gstreamer message stream-start ==> pipeline0
[gstreamer] gstreamer changed state from PAUSED to PLAYING ==> v4l2src0
video-viewer: failed to capture video frame
[gstreamer] gstCamera – onPreroll
[gstreamer] gstCamera recieve caps: video/x-raw, format=(string)YUY2, width=(int)640, height=(int)480, pixel-aspect-ratio=(fraction)1/1, framerate=(fraction)30/1, colorimetry=(string)2:4:5:1, interlace-mode=(string)progressive
[gstreamer] gstCamera – recieved first frame, codec=raw format=yuyv width=640 height=480 size=614400
video-viewer: failed to capture video frame
RingBuffer – allocated 4 buffers (614400 bytes each, 2457600 bytes total)
[gstreamer] gstreamer changed state from READY to PAUSED ==> mysink
[gstreamer] gstreamer message async-done ==> pipeline0
[gstreamer] gstreamer changed state from PAUSED to PLAYING ==> mysink
[gstreamer] gstreamer changed state from PAUSED to PLAYING ==> pipeline0
RingBuffer – allocated 4 buffers (921600 bytes each, 3686400 bytes total)
video-viewer: captured 1 frames (640 x 480)
[OpenGL] glDisplay – set the window size to 640x480
[OpenGL] creating 640x480 texture (GL_RGB8 format, 921600 bytes)
[cuda] registered openGL texture for interop access (640x480, GL_RGB8, 921600 bytes)

I can’t figure out why it doesn’t work
, it seems to parse the parameter but then ignores it?

I’m running the latest image and have built jetson-inference from source a few days back.

Any ideas why it doesn’t work?

2

Oh snap, i just noticed an important detail in the docs:

–input-flip=FLIP flip method to apply to input (excludes V4L2):

So i guess i should ask a different question then. How do I flip an image coming from a USB camera from python?

3

You may want to try cv2.flip() - Python OpenCV – cv2.flip() method - GeeksforGeeks

You can use cudaToNumpy() and cudaFromNumpy() to get the image into numpy array and back again after done flipping.

4

Thank you.

In the end I modified the jetson-inference/utils/camera/gstCamera.cpp
Changed:
ss << “appsink name=mysink”;
to:
ss << “videoflip video-direction=180 ! appsink name=mysink”;

then went to jetson-inference/utils
and ran:
make
sudo make install

(for future reference) :)

Its not python, but it feels like its less overhead this way. I think im going to stick with it. Would be nice if we could just pass extra gstreamer stuff as an argument for V4L2 cameras.

5

OK cool, yes that is probably less overhead. Perhaps I could implement the --input-flip argument this way for V4L2 cameras too - thanks.

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6

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