Jetson Nano Gstreamer Saving Video

Robotics & Edge Computing Jetson & Embedded Systems Jetson Nano
1

Hello,

I am using a Jetson Nano 4 GB model. I am trying to save a video capture frame-by-frame using VideoWriter with OpenCV. When the file is saved as an mp4, the output only shows a green screen for the recorded amount of time. The video capture is currently working and getting frames from the CSI camera.

Here is the VideoCapture gstreamer_pipeline:

def gstreamer_pipeline(
    sensor_id=0,
    capture_width=640,
    capture_height=480,
    display_width=320,
    display_height=240,
    framerate=15,
    flip_method=0,
):
    return (
        "nvarguscamerasrc sensor-id=%d !"
        "video/x-raw(memory:NVMM), width=(int)%d, height=(int)%d, framerate=(fraction)%d/1 ! "
        "nvvidconv flip-method=%d ! "
        "video/x-raw, width=(int)%d, height=(int)%d, format=(string)BGRx ! "
        "videoconvert ! "
        "video/x-raw, format=(string)BGR ! appsink"
        % (
            sensor_id,
            capture_width,
            capture_height,
            framerate,
            flip_method,
            display_width,
            display_height,
        )
    )

Here is the VideoWriter gstreamer_pipeline [does not work]:

        gstreamer_pipeline = (
        "appsrc caps=video/x-raw,format=BGR,width=640,height=480,framerate=15/1 ! "
        "videoconvert ! video/x-raw,format=I420 ! x264enc ! mp4mux ! filesink location=output.mp4")
        out = cv.VideoWriter(gstreamer_pipeline, cv.CAP_GSTREAMER, 25, (640, 480), True)

Thank you Friend,
Friend.

3

Hi,
For generating a valid mp4 we would need to send EoS in terminaation. It is to add -e in gst-launch-1.0. Not sure this works in cv2.VideoWriter() but please give it a try.

Or you may try to save to a mkv file like this sample:
Displaying to the screen with OpenCV and GStreamer - #9 by DaneLLL

4

Hello DaneLLL,

Thank you for replying. I’ll see if that works for cv2.VideoWriter().

With the link you referred to, you have the following code for the VideoCapture()

    cap = cv2.VideoCapture("filesrc location=/home/nvidia/sample_1080p_h264.mp4 ! qtdemux ! h264parse ! nvv4l2decoder ! nvvidconv ! video/x-raw, format=BGRx ! videoconvert ! video/x-raw,format=BGR ! appsink  ")

Is it alright if I take the video footage straight from the CSI camera? The code above currently allows me to capture video from the CSI camera and display it (but get the incorrect recording footage → green video).

5

Hi,
The sample does not exactly fit your use-case. For CSI camera input, your cv2.VideoCapture() looks good.

1 Like
6

I’ll let you know if it works in the next upcoming days.

Thank you friend

7

Thank you @DaneLLL!

The sample code that you provided worked! With a few tweaks to the VideoCapture Pipeline, I was able to achieve a connection with the CSI camera. The VideoWriter that you have provided via the link worked perfectly!

Here is the updated code that achieves a CSI input and video recorded feedback:

import sys
import cv2 as cv

def gstreamer_pipeline(
    sensor_id=0,
    capture_width=1280,
    capture_height=720,    
    display_width=320,
    display_height=240,
    framerate=15,
    flip_method=0,
):
    return (
        "nvarguscamerasrc sensor-id=%d !"
        "video/x-raw(memory:NVMM), width=(int)%d, height=(int)%d, framerate=(fraction)%d/1 ! "
        "nvvidconv flip-method=%d ! "
        "video/x-raw, width=(int)%d, height=(int)%d, format=(string)BGRx ! "
        "videoconvert ! "
        "video/x-raw, format=(string)BGR ! appsink"
        % (
            sensor_id,
            capture_width,
            capture_height,
            framerate,
            flip_method,
            display_width,
            display_height,
        )
    )

def read_cam():
    cap = cv.VideoCapture(gstreamer_pipeline(flip_method=0), cv.CAP_GSTREAMER)

    w = cap.get(cv.CAP_PROP_FRAME_WIDTH)
    h = cap.get(cv.CAP_PROP_FRAME_HEIGHT)
    fps = cap.get(cv.CAP_PROP_FPS)
    print('Src opened, %dx%d @ %d fps' % (w, h, fps))

    gst_out = "appsrc ! video/x-raw, format=BGR ! queue ! videoconvert ! video/x-raw,format=BGRx ! nvvidconv ! nvv4l2h264enc ! h264parse ! matroskamux ! filesink location=test.mkv "
    out = cv.VideoWriter(gst_out, cv.CAP_GSTREAMER, 0, float(fps), (int(w), int(h)))
    if not out.isOpened():
        print("Failed to open output")
        exit()

    if cap.isOpened():
        while True:
            ret_val, img = cap.read()
            if not ret_val:
                break
            out.write(img)
            cv.waitKey(1)
    else:
     print("pipeline open failed")

    print("successfully exit")
    cap.release()
    out.release()


if __name__ == '__main__':
    read_cam()
1 Like
8

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