xiaoqiang tutorial (21) get USB camera 30fps 1080p image stream and 120fps VGA resolution image stream
Xiaoqiang's default USB camera node publishes a 30fps VGA (640*480) image stream that can satisfy most visual tasks. The USB camera hardware can actually output 120fps VGA image stream and up to 30fps 1080p image stream. This article will introduce how to obtain these two type of the image.
1.Upgrade usb_cam node source code
Taking into account the USB2.0 bandwidth, output 120fps VGA video and 30fps 1080p video, need to use mjpeg format. For Xiaoqiang's own USB camera ROS driver package usb_cam, it can not read Xiaoqiang usb camera in mjpeg way, so we need to upgrade usb_cam first. For the upgrade method, please refer to this post
2.Test 120fps VGA video output
First please turn off Xiaoqiang's startup task
sudo service startup stop
Modify the contents of the ov2610mjpg.launch file in the usb_cam package as shown below
<launch>
<node name="camera_node" pkg="usb_cam" type="usb_cam_node">
<param name="video_device" value="/dev/video0" />
<param name="image_width" value="640" />
<param name="image_height" value="480" />
<param name="framerate" value="120" />
<param name="pixel_format" value="mjpeg" />
<param name="camera_frame_id" value="ov2610" />
<param name="io_method" value="mmap"/>
</node>
</launch>
Launch the above launch file
roslaunch usb_cam ov2610mjpg.launch
Open a new window to print the published image topic frame rate
rostopic hz /camera_node/image_raw
Normal output similar to the following figure
subscribed to [/camera_node/image_raw]
average rate: 99.497
min: 0.004s max: 0.016s std dev: 0.00246s window: 98
average rate: 99.324
min: 0.004s max: 0.016s std dev: 0.00240s window: 198
average rate: 99.385
min: 0.004s max: 0.016s std dev: 0.00236s window: 297
average rate: 99.247
min: 0.004s max: 0.016s std dev: 0.00236s window: 396
average rate: 99.302
min: 0.004s max: 0.016s std dev: 0.00232s window: 495
average rate: 99.296
min: 0.004s max: 0.016s std dev: 0.00231s window: 595
average rate: 99.249
min: 0.004s max: 0.016s std dev: 0.00230s window: 694
The above output shows that the camera frame rate is about 99fps and does not reach 120fps. This is due to the influence of ambient light, which can reach 120 frames if the ambient light is sufficient.
2.Test 1080p video output at 30fps
First please stop Xiaoqiang's startup service
sudo service startup stop
Modify the contents of the ov2610mjpg.launch file in the usb_cam package as shown below.
<launch>
<node name="camera_node" pkg="usb_cam" type="usb_cam_node">
<param name="video_device" value="/dev/video0" />
<param name="image_width" value="1920" />
<param name="image_height" value="1080" />
<param name="framerate" value="30" />
<param name="pixel_format" value="mjpeg" />
<param name="camera_frame_id" value="ov2610" />
<param name="io_method" value="mmap"/>
</node>
</launch>
Launch the above launch file
roslaunch usb_cam ov2610mjpg.launch
Open a new window to print the published image topic frame rate.
rostopic hz /camera_node/image_raw
Normal output similar to the following figure.
xiaoqiang@xiaoqiang-desktop:~$ rostopic hz /camera_node/image_raw
subscribed to [/camera_node/image_raw]
average rate: 29.986
min: 0.028s max: 0.039s std dev: 0.00318s window: 30
average rate: 29.917
min: 0.028s max: 0.039s std dev: 0.00296s window: 59
average rate: 29.912
min: 0.028s max: 0.039s std dev: 0.00292s window: 89
average rate: 29.853
min: 0.027s max: 0.042s std dev: 0.00308s window: 119
average rate: 29.874
min: 0.027s max: 0.042s std dev: 0.00283s window: 149
average rate: 29.839
min: 0.027s max: 0.042s std dev: 0.00282s window: 179
average rate: 29.849
min: 0.027s max: 0.042s std dev: 0.00282s window: 202