I have a confusion regarding using CNN (VGG, ResNet) as a backbone of U-net using the segmentation library. My input shape is 512x512x3. As far I’ve understood in U-net the skip connection is used in before every layer where a downsampling happes (example: maxpool for VGG or conv with 2x2 stride for ResNet).But, in the model summary for both VGG and ResNet-based backbone I see the skip connection is there from the second downsampling (256x256x64), but there is no skip connection from the 512 resolution. Can someone explain the reasons? please check the detailed diagram of VGG19 for reference here: https://i.stack.imgur.com/FBqUy.png
I have a confusion regarding using CNN (VGG, ResNet) as a backbone of U-net using the segmentation library. My input shape is 512x512x3. As far I’ve understood in U-net the skip connection is used in before every layer where a downsampling happes (example: maxpool for VGG or conv with 2x2 stride for ResNet).But, in the model summary for both VGG and ResNet-based backbone I see the skip connection is there from the second downsampling (256x256x64), but there is no skip connection from the 512 resolution. Can someone explain the reasons? please check the detailed diagram of VGG19 for reference here: https://i.stack.imgur.com/FBqUy.png