I am using a depthai OAK-D4 module. I am using Video Encoder Node to convert the ColorCamera Node output to get h264 encoded video data so I can Publish it to ROS topic using bridge.cv2_to_imgmsg . But I cannot figure out how to use the bitstream given by VideoEncoder Node.

`
import depthai as dai
import numpy as np
import rospy,cv2
from sensor_msgs.msg import Image
from cv_bridge import CvBridge, CvBridgeError

pub = rospy.Publisher('/webcamEnc',Image,queue_size= 10)
pub1 = rospy.Publisher('/webcamRGB',Image,queue_size= 10)
rospy.init_node('image',anonymous = True)
pipeline = dai.Pipeline()

camRgb = pipeline.create(dai.node.ColorCamera)
videnc = pipeline.create(dai.node.VideoEncoder)

xoutRgb = pipeline.create(dai.node.XLinkOut)
encout = pipeline.create(dai.node.XLinkOut)

xoutRgb.setStreamName("rgb")
encout.setStreamName("h264")

camRgb.setPreviewKeepAspectRatio(False)
camRgb.setPreviewSize(320,320)
camRgb.setInterleaved(True)
camRgb.setColorOrder(dai.ColorCameraProperties.ColorOrder.BGR)
videnc.setDefaultProfilePreset(30,dai.VideoEncoderProperties.Profile.MJPEG)

camRgb.preview.link(xoutRgb.input)
camRgb.video.link(videnc.input)
videnc.bitstream.link(encout.input)

bridge = CvBridge()
print(videnc.getFrameRate())
with dai.Device(pipeline) as device:
qRgb = device.getOutputQueue(name="rgb", maxSize=2, blocking=False)
qenc = device.getOutputQueue(name="h264",maxSize=1, blocking=False)
print("Type(RGB):",qRgb.get().getType()," Type(ENC):",qenc.get().getType())
qenc.get().setType(qRgb.get().getType())
print(qenc.get().getType())
while True:
rgbFrame = qRgb.get().getCvFrame()
encFrame = qenc.get().getFrame()
if not rospy.is_shutdown():
msg1 = bridge.cv2_to_imgmsg(rgbFrame,encoding='bgr8')
pub1.publish(msg1)
msg = bridge.cv2_to_imgmsg(encFrame,encoding='bgr8')
pub.publish(msg)
`

  • erik replied to this.

    Hello microzic ,
    I am not sure whether ROS even has (widespread) support for H264/H265 messages - I only found CompressedImages, which are jpeg/png. WHile learning ROS recently, I wrote the code below to stream JPEG encoded frames, which I hope will help.
    Thanks, Erik

    #!/usr/bin/env python
import rospy
import depthai as dai
import numpy as np
from sensor_msgs.msg import CompressedImage

def main():
    # Create pipeline
    pipeline = dai.Pipeline()

    camRgb = pipeline.create(dai.node.ColorCamera)

    videoEnc = pipeline.create(dai.node.VideoEncoder)
    videoEnc.setDefaultProfilePreset(30, dai.VideoEncoderProperties.Profile.MJPEG)
    camRgb.video.link(videoEnc.input)
    
    xoutVideo = pipeline.create(dai.node.XLinkOut)
    xoutVideo.setStreamName("mjpeg")
    videoEnc.bitstream.link(xoutVideo.input)

    pub = rospy.Publisher('camera/color/bgr', CompressedImage, queue_size=10)
    rospy.init_node('talker', anonymous=True)

    # Connect to device and start pipeline
    with dai.Device(pipeline) as device:
        q = device.getOutputQueue(name="mjpeg", maxSize=1, blocking=False)

        while True and not rospy.is_shutdown():
            msg = CompressedImage()
            msg.header.stamp = rospy.Time.now()
            msg.format = "jpeg"
            msg.data = np.array(q.get().getData()).tobytes()

            pub.publish(msg)

if __name__ == '__main__':
    main()

      Thanks Erik. It helped a lot. I was able to transmit a 1080 video with almost no delay.

      Perfect, I'm glad it helped!

      a year later