some questions about offset&steps

[CrazySssst]

question about offset:
i found that you set offsets=[2.5, 2.5, 10.5, 26.5, 90.5, 160.5] in ssd_pascal_resnet_321.py , but offset is 0.5 in origin ssd(VGG), my question is:
1.why you do these changes?
2.how select the value of offset ( i mean why you use 2.5 instead of 1.5 or 3 )?

question about steps:
step of res7_relu (6 x 6) and res8_relu(3 x 3) are equal , you set them to 64 , but their resolutions are different. could you give some explains?

[caiqi]

@CrazySssst hi, have you figured out why the offsets should be [2.5, 2.5, 10.5, 26.5, 90.5, 160.5]? I think at least offsets should be less than 1.0 for original ssd's code. Here the start looks like equaling to offset * step.

[CrazySssst]

@chengyangfu @caiqi yes, i have the same confusion as you .
in dssd branch , i find these code in prior_box_layer.cpp

 for (int h = 0; h < layer_height; ++h) {
    for (int w = 0; w < layer_width; ++w) {
      float center_x = (w + offset_) * step_w;
      float center_y = (h + offset_) * step_h;

and
offset_ = prior_box_param.offset();
i can't understand the mean of (w+160.5)*step_w.
maybe author forgot to update this file?

[qianwangn]

@CrazySssst Hi,do you find out how to change the offset to get the correct result ?

[foralliance]

@CrazySssst
@caiqi
@johnlanbor
@chengyangfu
Hi

have u solve the problem？？