Open neeveermoree opened 4 years ago
I have same question.
But many SSD's implementation use s_1 = 0.1
.
e.g.) ssd.pytorch
...
s_k = self.min_sizes[k]/self.image_size
...
min_size = [30, 60, 11, 262, 213, 264]
. So, s_1 =30/300=0.1
.
Where s_k=0.1
is from?? I can't find one in original paper...
Author says "An alternative way of improving SSD is to design a better tiling of default boxes so that its position and scale are better aligned with the receptive field of each position on a feature map. We leave this for future work."
s_1=0.1
may be from feature work :(
EDIT: chainercv's issue comments helped me.
Hello, it's been a while since I read the paper, so I don't remember my thought process regarding why I went ahead with a scale of 0,1 for conv4_3
.
Looking at the paper now, in Section 3.1 (Page 7), it is stated the conv4_3
will use a scale of 0.1.
We set default box with scale 0.1 on
conv4_3
.
So does this mean s_min
is now 0.1? Apparently not, because the paper treats conv4_3
as somewhat of a special case and considers s_min
to be the scale of conv7
instead. And from conv7
onwards, they are regularly spaced up to s_max
.
This is apparent in their wording throughout the paper. At the end of page 7:
For SSD512 model, we add extra
conv12_2
for prediction, sets_min
to 0.15, and 0.07 onconv4_3
.
Here too, the scale for conv4_3
is set separately.
On page 11:
We follow the strategy mentioned in Sec. 2.2, but now our smallest default box has a scale of 0.15 instead of 0.2, and the scale of the default box on
conv4_3
is 0.07 (e.g. 21 pixels for a 300 × 300 image)For SSD512 model, we add extra
conv12_2
for prediction, sets_min
to 0.1, and 0.04 onconv4_3
.
I don't remember if my understanding of this is as clear now as it was when I wrote the code, but this is all I can tell you now, off the top of my head. I'm sure I must have been confused at that time too, and I must've checked with other repositories to confirm. This paper is a little too empirical sometimes.
@sgrvinod
We set default box with scale 0.1 on conv4_3.
Oh, it's written!!! Thanks a lot! You saved a lot of my time!
which relationship between anchors and min_size. Suppose I have 6 anchors box (w:h) (100,50)(125:75)(150:175), (175,180),(205,175),(235,153). How to calculate min_size, max_size. Thanks in advance if share the formular.
These are the values used in
In paper this values are used:
Proper values are:
0.2 , 0.34, 0.48, 0.62, 0.76, 0.9
Code to check: