Contents
What is anchor in RCNN?
Anchor boxes eliminate the need to scan an image with a sliding window that computes a separate prediction at every potential position. This convolutional correspondence means that a CNN can extract image features for an entire image at once.
Why is RCNN faster?
The reason “Fast R-CNN” is faster than R-CNN is because you don’t have to feed 2000 region proposals to the convolutional neural network every time. Instead, the convolution operation is done only once per image and a feature map is generated from it.
How faster RCNN have improves the fast RCNN?
In terms of Detection time, Faster R-CNN is faster than both R-CNN and Fast R-CNN. The Faster R-CNN also has better mAP than both the previous ones. The above Detection time results are from the research paper.
How many anchor boxes are used in Faster RCNN?
Faster RCNN uses anchor boxes of 3 aspect ratios and 3 scales. Thus for each pixel in the feature map, there are 9 anchor boxes. The architecture is a simple convolution layer with kernel size 3*3 followed by two fully connected layers (one for objectness score (classification) and other for regression of proposals).
Which is faster selective search or Faster RCNN?
The objectness measures score between object and background (thus low score for background and higher for regions with object). The region proposal time with selective search is 2 sec per image, whereas with RPN it’s just 10ms. Faster RCNN uses anchor boxes of 3 aspect ratios and 3 scales.
What is the purpose of Faster RCNN and CNN?
Faster RCNN is a third iteration of the RCNN “ Rich feature hierarchies for accurate object detection and semantic segmentation ”. R stands for regions and cnn stands for convolutional neural networks. The main objective of faster rcnn is to reduce the computational expenses and to work at able to work at real time.
How to assign a positive label to a CNN anchor?
In the faster R-CNN paper, the author uses two conditions to assign a positive label to an anchor. These are : those anchors which have the highest Intersection-over-Union (IoU) with a ground-truth box, or an anchor that has an IoU overlap higher than 0.7 with any ground-truth box.