Description

Package implementing image-based machine learning with the MxNet platform. This code and documentation was developed for those working with the Rover Robotics OpenRover (TX1 or TX2). However, it should work for anyone with a compatible NVidia JetPack installed TX1 and TX2 (see below in install instructions).

Install from source

Requirements

If using a NVIDIA TX1

  • Jetpack 3.1
  • CUDA 8.0
  • cuDNN 6.0.21
  • OpenCV 2.4.12.1 (stock NVidia JetPack components)

If using a NVIDIA TX2

  • Jetpack 3.2.1
  • CUDA 9.0
  • cuDNN 7.0.5.15
  • OpenCV 3.3.1 (stock NVidia JetPack components)

Install ROS Package

cd ~/catkin_ws/src/
git clone https://github.com/RoverRobotics/rr_mxnet

Download Pre-Built MXNet Bindings

Unzip the TX and GluonCV bindings and copy to either the /usr/local/lib/python2.7/dist-packages/ or the ~/.local/lib/python2.7/dist-packages/ area. There may be additional dependencies required to load GluonCV, at minimum it requires scipy and the tqdm progress meter. After unpacking the relevant TX and GluonCV bindings, test they will load in python. Note, GluonCV is in active development and if you have issues, try the nightly build (pip install gluoncv --pre). This GluonCV snapshot zip (commit 6721429cb93637a0f9a7ec8a85deea4d43cb5d62) was verified to work with SSD and segmentation networks.

unzip mxnet_<target>_bindings_<jetpack_cuda_cudnn string>.zip
sudo mv mxnet_<target>_bindings_<jetpack_cuda_cudnn string>/mxnet-1.3.0-py2.7.egg /usr/local/lib/python2.7/dist-packages/.

unzip gluon-cv-0.3.zip
mv gluoncv ~/.local/lib/python2.7/dist-packages/

sudo apt install python-scipy
sudo pip install tqdm

Add a link to this package in easy-install.pth in the /usr/local/lib/python2.7/dist-packages/ subdirectory:

./mxnet-1.3.0-py2.7.egg

Install required python libraries:

sudo apt-get install python-opencv python-matplotlib python-numpy

Test MxNet Installation

python
>>> import mxnet as mx
>>> mx.__version___
'1.3.0'
>>> import gluoncv
>>> gluoncv.__version__
'0.3.0'
>>> print mx.nd.zeros((5,5),ctx=mx.gpu(0))

[[ 0.  0.  0.  0.  0.]
 [ 0.  0.  0.  0.  0.]
 [ 0.  0.  0.  0.  0.]
 [ 0.  0.  0.  0.  0.]
 [ 0.  0.  0.  0.  0.]]
<NDArray 5x5 @cpu(0)>

If you're working on a computer other than the TX1 or TX2, and/or if the above bindings didn’t work for you, follow the mxnet documentation on installation and if you are lucky, pip will work for you. If not, install from source.

Download and Run an Example Model

The model parameters for several SSD (single shot detection) networks are provided by GluonCV, based on MxNet. These will be downloaded automatically by specifying the relevant network in the launch file for fast and accurate object detection. Several example networks provided out-of-the-box with gluoncv include ResNet50, ResNet100, VGG16, mobilenet1.0 among others. See GluonCV's Detection Model Zoo for up-to-date models. Here is the relevant line in the launch file for loading a resnet50 (v1) based SSD, trained on the 20-class VOC dataset and intended to be run on 512x512 sized images:

    <param name="network" value="ssd_512_resnet50_v1_voc" />

Test the detector with an image being published to /usb_cam/image run:

roslaunch rr_mxnet example-resnet50-20classes.launch

View detections with rqt_image_view

rqt_image_view

Choose /rr_mxnet/image topic from the dropdown menu. If all is working well, you should see fresh images and possibly detections overlain on the image.

Troubleshooting

If you do not see output, first check the node started and check that mxnet is working. The node should output a line indicating it has initialized with the selected model file like so:

[INFO] [1537973019.312896]: [MxNet Initialized with model ssd_512_resnet50_voc]

If instead the node gives an error starting MxNet, the following areas should be checked: the MxNet bindings, GluonCV bindings, the model name or CUDA/cuDNN/NVidia driver setup.

Nodes

SSD Object Detection Semantic Segmentation

mxnet_ssd_node

The mxnet_ssd node runs a single shot detector on images from a subscribed image topic and publishes localization and classification predictions from a pre-defined list of classes. The localization consists of relative bounding box locations with respect to the full image size (xmin, ymin, xmax, ymax) and the classification consists of a number between 0 and 20 which is converted to a meaningful object string in the detections topic. The actual detection is performed on a 512x512 resized image that is cropped out of the subscribed image topic. This node can be configured to crop and resize a single image out of the image topic or it can be configured to perform a sliding-window set of crops on the image for better distance detection.

SSD is a single-shot detector, so why are we specifying a sliding window pattern?

To improve on distance detection. The detection layers require meaningful features to produce detections and features only start being useful after a few depths of layers (ever since VGG16 the deeper detectors have won ImageNet) and in order to reduce memory, the first few layers also perform downsampling as they go, so we don’t get useful features until ~16-fold reduction in the image. Therefore, to get the best distance detection, we also use a sliding window method to best match SSD’s capabilities with what we want out of it. However, this will take more time to complete each set of detections, so find the tradeoff that works best for you. Note, your camera image quality will be more important for longer distance performance. If you have a 5 megapixel image, try zooming in to a 500x500 crop of the image - if this is zoom is noticeably blurry, you will not get as much benefit from a sliding window. <show example images?> For the first-level sliding window we only need to specify the number of crops across the larger image dimension (typically width) as it will take crops that are sized to the smaller image dimension (e.g. height). For the second-level sliding window, we need to specify the number of crops across both dimensions and the crop size. The detector will work out the resulting overlap of the crops (depends on your application, you could aim for 20% at first) and report this in both dimensions on the node standard output. This will require a little trial and error to tune.

Image Sizes

A brief aside on image sizes, most often the x-dimension (width) of an image is larger than the y-dimension (height), with an aspect ratio of 4:3 being common (e.g. 640x480 images have an aspect ratio of 4:3). However, the detector can only accept square image inputs, so if you are not specifying a sliding window crop, you have two choices: 1) resize the non-square image to square, which will squish one dimension, or 2) center crop the non-square image to a square image with the same minimum dimension (e.g., a 640x480 image could be cropped to 480x480, discarding a column of 15% of the pixels on each side). It is possible someone will have a vertical camera and want to use this code, so we let you configure this. By default the code will center-crop.

Subscribed Topics

/rr_mxnet_ssd/enable std_msgs::Bool

  • Controls whether detection is run on the subscribed image topic. This is used to enable and disable the heavy processing required for detection as needed. By default, the node will start disabled unless specified in the start_enabled parameter.

/rr_mxnet_ssd/zoom std_msgs::Bool

  • Controls whether a second layer of detection with a sliding window is enabled. By default, zoom mode is disabled unless specified in the zoom parameter.

/usb_cam/image_raw sensor_msgs::Image

  • Image topic to perform detections on.

/rr_mxnet_segmentation/segmentation_mask sensor_msgs::Image

  • Image mask topic to restrict detections. Must be same sized image as the image topic for detections.

/rr_mxnet_ssd/mask_overlap std_msgs::Int32

  • Ranges from 0 to 100. Controls whether to use a mask to restrict detections. If ~mask_overlap is set greater than 0, then object detections are restricted to boxes that overlap at least the mask_overlap percentage with mask==255 pixels. Conversely, if ~mask_overlap is set to 0, then the mask is ignored.

Published Topics

~/image sensor_msgs::Image ~/image/compressed sensor_msgs:CompressedImage

  • Only published if ~publish_detection_images is set to True. Publishes images with bounding boxes and detection strings overlain.

~/detections vision_msgs::Detection2DArray

  • Publishes object detections in an array of Detection2D.

Parameters

~image_topic (String, default "/usb_cam/image_raw")

  • Image topic to perform detections on.

~detections_topic (String, default ~/detections)

  • Detections2DArray topic to publish detections.

~image_detections_topic (String, default ~/image)

  • Image topic to publish images with detections overlain.

~throttle_timer (Int32, default 5)

  • Seconds to wait between detections. If timer is set to less than the possible detection rate, the node will run inference as fast as possible and probably take up most of the computer's resources (CPU or GPU).

~latency_threshold (Int32, default 2)

  • Seconds to allow the images to get stale before discarding and waiting for next new image. In the worst case, if there is substantial time delay between the image publisher and reception of images by this node, this may need to be increased just to allow the node to function. In typical low latency systems, this can be decreased.

~start_enabled (Bool, default False)

  • Use this to have the detector start running as soon as it is loaded.

~publish_detection_images (Bool, default False)

  • Publish or do not publish images with bounding boxes and detection classes displayed.

~start_zoom_enabled (Bool, default False)

  • Enables a sliding window for the detector. Requires more time to complete each detection. Allows for longer distance detection. For an example of a sliding window detector.

~mask_overlap (Int32, default 0)

  • Ranges from 0 to 100. Controls whether to use a mask to restrict detections. If ~mask_overlap is set greater than 0, then object detections are restricted to boxes that overlap at least the mask_overlap percentage with mask==255 pixels. Conversely, if ~mask_overlap is set to 0, then the mask is ignored. Can be set in real time and overridden by the mask_overlap topic above.

MxNet Settings

~threshold (Float, default 0.5)

  • Detection probability threshold. If set high, only high-confidence detections will be reported. Note, probability does not linearly correspond to actual likelihood that something is what it is, but it is a useful guide as a start. Lower thresholds will result in less missed detections but more false positives.

~batch_size (Int32, default 1)

  • The number of images to pass to the GPU (if enabled) at once. This increases GPU memory used but, if any sliding window cropping is used, speeds up the detection. There is a limit on GPU memory, and if this is reached the node will crash. There is not a simple method to determine this ahead of time, and this is instead to be determined using a short period of trial and error to find the limit. In order to maximize efficiency, you should either set this to level0_ncrops (if no zoom) or some larger divisible portion of the total number of crops that will be used (if zooming). It does not need to be an even divisor of the total number of crops, the code will maximize usage of available batch size and number of crops.

~model_directory (String, default "~/mxnet/ssd")

  • Location of the MxNet model parameters and symbol on disk.

~model_filename (String, default "ssd_512_resnet50_v1_voc.params")

  • Name of the MxNet model to load and run. This is ignored if using a stock network (see ~network below). This is intended to be used if you have custom network weights installed in the model_directory location.

~network (String, default "ssd_512_resnet50_v1_voc")

. Name of the network symbol to load. Choices include "ssd_512_resnet50_v1_voc", "ssd_512_resnet50_v1_coco", "ssd_512_resnet50_v1_custom" and similar with mobilenet1.0, vgg16. See GluonCV's Detection Model Zoo for a more complete list.

~enable_gpu (Bool, default false)

  • Use the GPU or CPU for inference.

~classes (String, default "aeroplane, bicycle, bird, boat, bottle, bus,car, cat, chair, cow, diningtable, dog, horse, motorbike,person, pottedplant, sheep, sofa, train, tvmonitor")

  • The names of classes used to train the model (the VOC-trained models used 20 classes), separated by commas.

Crop Pattern

~level0_ncrops (Int32, default 1)

  • Specify the sliding window detection pattern in the larger image dimension (typically this is the x-dimension, or width). The square crop will be sized to the smaller image dimension (typically the y-dimension, or height). Assuming width is the larger dimension, how many crops in the left-right direction of the image should we pass to the detector? The detector code will work out the overlap and report it on the node launch standard output and ROS logfile. In general, the number of x crops should be set to close to 20-30% more than the image width divided by the detector input size (512). For example, with image width 1280, use level1_xcrop=3 and the detector will see 22% overlap on the inner crops with each of the outer crops. If set to 0, this will take the minimum of x-dimension and y-dimension and center crop to that resolution, unless resize_square is set to True. If set to 1, then this will center crop to the minimum image dimension. If set to 0, then the image will be resized to square first and the whole image will be used. For example, if you set this to 0 and your image size is 1920x1280, then the detector will resize the image to square before passing it in, otherwise if set to 1, it will center crop to 1280 by 1280 pixels and pass the 1280x1280 image to the detector.

~level1_xcrops (Int32, default 0)

  • Specify the second-level sliding window detection pattern in the x-dimension on the second layer. Use this to create a second layer set of sliding window zooms in to the image. Please note, this should be greater than 1 to be useful otherwise it will only create a crop in the upper left corner of the image. The crops will be distributed across the image and the overlap percentage will be reported so watch the overlap percentage and try to get it above 0% but below 50% to maximize detectability of small objects.

<TODO: images of crop patterns>

~level1_ycrops (Int32, default 0)

  • Specify the sliding window pattern in the y-dimension. This must be greater than 1 to have any effect, or turn it off by leaving as 0.

~level1_crop_pixels (Int32, default 300)

  • The size of pixels to be used in the second-level crop. In general, this should be set to produce images of size 300x300 or so to be passed to the detector, which will upsample them to 512 by 512 before running detection. As discussed in the node description, this will nevertheless improve distance detection if the image quality is good.

Save Parameters

~save_detections (Bool, default False)

. Save detected images in jpeg form, with incrementing number.

~save_directory (String, default "/tmp")

. Directory to save detection images.

Example Launch File

<launch>
  <node name="rr_mxnet_ssd" pkg="rr_mxnet" type="mxnet_ssd_node.py" output="screen" >
    <param name="image_topic" value="/usb_cam/image_raw" />
    <param name="mask_topic" value="/rr_mxnet_segmentation/segmentation_mask" />
    <param name="detections_topic" value="~detections" />
    <param name="publish_detection_images" value="false" type="bool" />
    <param name="image_detections_topic" value="~image" />
    <param name="throttle_timer" value="5" type="int" />
    <param name="threshold" value="0.5" type="double" />
    <param name="start_enabled" value="false" type="bool" />
    <param name="start_zoom_enabled" value="false" type="bool" />
    <param name="level0_ncrops" value="2" type="int" />
    <param name="level1_xcrops" value="4" type="int" />
    <param name="level1_ycrops" value="2" type="int" />
    <param name="level1_crop_size" value="380" type="int" />
    <param name="enable_gpu" value="true" type="bool" />
    <param name="classes" value="aeroplane, bicycle, bird, boat, bottle, bus,car, cat, chair, cow, diningtable, dog, horse, motorbike,person, pottedplant, sheep, sofa, train, tvmonitor" />
    <param name="batch_size" value="1" type="int" />
    <param name="network" value="ssd_512_resnet50_v1_voc" />
    <param name="model_filename" value="ssd_512_resnet50_v1_voc.params" />
    <param name="save_detections" value="false" type="bool" />
    <param name="save_directory" value="/tmp" />
  </node>
</launch>

mxnet_segmentation_node

Semantic segmentation using pretrained segmentation networks from GluonCV, see segmentation model zoo for a list of relevant pre-trained segmentation networks.

Published Topics

~/segmentation_mask sensor_msgs::Image, latched output

  • Published segmentation mask (0 or 255, corresponding to mask_values rosparam). Note, this output is latched, so the timestamp seen by subscribers will gradually get older if no new detection requested.

~/segmentation_overlay sensor_msgs::Image

  • Published segmentation, masked corresponding to mask_values rosparam, and overlain on input image in red at 50% alpha blend.

Subscribed Topics

/usb_cam/image_raw sensor_msgs::Image

  • Input image to run segmentation on.

/rr_mxnet_segmentation/run_once std_msgs::Bool

  • Enable the detector and run segmentation once (or number of frames specified in rosparam ~avg_segmentation_frames). Segmentation may already be running continuously (if appropriate rosparam or topic run_continuous is set) or alternatively if run_continuous is False, it can be run once on run_once=True and some number of frames (or single frame) averaged before publishing the output mask. Test with:

rostopic pub /rr_mxnet_segmentation/run_once std_msgs/Bool "data: true" -1

/rr_mxnet_segmentation/run_continuous std_msgs::Bool

  • Segmentation runs continuously if rosparam run_continuous is True or receive True on this topic.

Parameters

~image_topic (String, default "/usb_cam/image_raw")

  • Input image topic to perform detections on.

~mask_topic (String, default "~segmentation_mask", latched=True)

  • Output image topic to publish segmentation result.

~overlay_topic (String, default "~segmentation_overlay")

  • Output image topic to publish segmentation result overlain in red on input image.

~run_continuous (Bool, default False)

  • Segmentation runs as fast as possible within limits set by throttle timer if this is set True.

~mask_values (String, default "9, 12")

  • Pixel values to use to generate a "True" mask. These values in the semantic segmentation output are used to set the output mask==255. All other segmentation pixel values get mask==0. Alternatively, if set to negative values (e.g. "-9, -12"), the opposite masking is used, so all segmentation pixel values that are either 9 or 12 get set to 0, and all other pixels get set to 255. For values of pixel masks, refer to the ADE20K or COCO mask values. For example with ADE20K, person=12, sky=2, grass=9, road=6, etc.

~network (String, default "deeplab_resnet50_ade")

. Name of the network symbol to load. Choices include "vgg_resnet50_ade", "psp_resnet50_ade", "deeplab_resnet50_ade" and others. See GluonCV's Segmentation Model Zoo for a more complete list.

~enable_gpu (Bool, default false)

  • Use the GPU or CPU for inference.

~throttle_timer (Int32, default 5)

  • Seconds to wait between segmentation runs. If timer is set to less than the possible inference rate, the node will run inference as fast as possible and probably take up most of the computer's resources (CPU or GPU).

~latency_threshold (Int32, default 2)

  • Seconds to allow the images to get stale before discarding and waiting for next new image. In the worst case, if there is substantial time delay between the image publisher and reception of images by this node, this may need to be increased just to allow the node to function. In typical low latency systems, this can be decreased.

Example Launch File

<launch>
  <node name="rr_mxnet_segmentation" pkg="rr_mxnet" type="mxnet_segmentation_node.py" output="screen" >
    <param name="image_topic" value="/usb_cam/image_raw" />
    <param name="mask_topic" value="~segmentation_mask" />
    <param name="overlay_topic" value="~segmentation_overlay" />
    <param name="enable_gpu" value="true" type="bool" />
    <param name="avg_segmentation_frames" value="5" type="int" />
    <param name="run_continuous" value="false" type="bool" />
    <param name="mask_values" value="9, 12" />
    <param name="throttle_timer" value="5" type="int" />
    <param name="latency_threshold" value="2" type="int" />
    <param name="network" value="deeplab_resnet50_ade" />
  </node>
</launch>

Release Notes

This package is currently in pre-release meaning the code has been tested and is functional, but backwards compatibility is not guaranteed until v1.0.0, so make note of which version you are using and read the changelog carefully before updating.

Wiki: rr_mxnet (last edited 2018-10-05 20:57:45 by ErikBeall)