Mask_rcnn: What is the meaning of BACKBONE_STRIDES?

[Mabinogiysk]

Is BACKBONE_STRIDES the feature map size in each stage?
If I change the image size from 128*128 to 512*512, should I change the value of BACKBONE_STRIDES?
Thanks!

[waleedka]

The backbone stride is the stride of each layer of the backbone network relative to the input image. For example, the C2 layer of the pyramid has a stride of 4, meaning that it's dimensions are 1/4 of the dimensions of the input image (i.e. if the input image is 1024x1024 the C2 size is 256x256).

Changing the input image size doesn't affect the backbone stride.

[John1231983]

@waleedka : What is BACKBONE_STRIDES value when I use resnet50 model, instead of 101? Because your document said that

The strides of each layer of the FPN Pyramid. These values
are based on a Resnet101 backbone.
BACKBONE_STRIDES = [4, 8, 16, 32, 64]

[waleedka]

Resnet50 has the same strides as Resnet101