# DetectionOutput¶

Versioned name : DetectionOutput-8

Category : Object detection

Short description : DetectionOutput performs non-maximum suppression to generate the detection output using information on location and confidence predictions.

Detailed description : Reference. The layer has 3 mandatory inputs: tensor with box logits, tensor with confidence predictions and tensor with box coordinates (proposals). It can have 2 additional inputs with additional confidence predictions and box coordinates described in the article. The output tensor contains information about filtered detections described with 7 element tuples: [batch_id, class_id, confidence, x_1, y_1, x_2, y_2]. The first tuple with batch_id equal to -1 means end of output.

At each feature map cell, DetectionOutput predicts the offsets relative to the default box shapes in the cell, as well as the per-class scores that indicate the presence of a class instance in each of those boxes. Specifically, for each box out of k at a given location, DetectionOutput computes class scores and the four offsets relative to the original default box shape. This results in a total of $$(c + 4)k$$ filters that are applied around each location in the feature map, yielding $$(c + 4)kmn$$ outputs for a m * n feature map.

Attributes :

NOTE : num_classes, a number of classes attribute, presents in DetectionOutput_1 has been removed. It can be computed as cls_pred_shape[-1] // num_prior_boxes where cls_pred_shape and num_prior_boxes are class predictions tensor shape and a number of prior boxes.

• background_label_id

• Description : background label id. If there is no background class, set it to -1.

• Range of values : integer values

• Type : int

• Default value : 0

• Required : no

• top_k

• Description : maximum number of results to be kept per batch after NMS step. -1 means keeping all bounding boxes.

• Range of values : integer values

• Type : int

• Default value : -1

• Required : no

• variance_encoded_in_target

• Description : variance_encoded_in_target is a flag that denotes if variance is encoded in target. If flag is false then it is necessary to adjust the predicted offset accordingly.

• Range of values : false or true

• Type : boolean

• Default value : false

• Required : no

• keep_top_k

• Description : maximum number of bounding boxes per batch to be kept after NMS step. -1 means keeping all bounding boxes after NMS step.

• Range of values : integer values

• Type : int[]

• Required : yes

• code_type

• Description : type of coding method for bounding boxes

• Range of values : “caffe.PriorBoxParameter.CENTER_SIZE”, “caffe.PriorBoxParameter.CORNER”

• Type : string

• Default value : “caffe.PriorBoxParameter.CORNER”

• Required : no

• share_location

• Description : share_location is a flag that denotes if bounding boxes are shared among different classes.

• Range of values : false or true

• Type : boolean

• Default value : true

• Required : no

• nms_threshold

• Description : threshold to be used in the NMS stage

• Range of values : floating-point values

• Type : float

• Required : yes

• confidence_threshold

• Description : only consider detections whose confidences are larger than a threshold. If not provided, consider all boxes.

• Range of values : floating-point values

• Type : float

• Default value : 0

• Required : no

• clip_after_nms

• Description : clip_after_nms flag that denotes whether to perform clip bounding boxes after non-maximum suppression or not.

• Range of values : false or true

• Type : boolean

• Default value : false

• Required : no

• clip_before_nms

• Description : clip_before_nms flag that denotes whether to perform clip bounding boxes before non-maximum suppression or not.

• Range of values : false or true

• Type : boolean

• Default value : false

• Required : no

• decrease_label_id

• Description : decrease_label_id flag that denotes how to perform NMS.

• Range of values :

• false - perform NMS like in Caffe*.

• true - perform NMS like in MxNet*.

• Type : boolean

• Default value : false

• Required : no

• normalized

• Description : normalized flag that denotes whether input tensor with proposal boxes is normalized. If tensor is not normalized then input_height and input_width attributes are used to normalize box coordinates.

• Range of values : false or true

• Type : boolean

• Default value : false

• Required : no

• input_height (input_width)

• Description : input image height (width). If the normalized is 1 then these attributes are not used.

• Range of values : positive integer number

• Type : int

• Default value : 1

• Required : no

• objectness_score

• Description : threshold to sort out confidence predictions. Used only when the DetectionOutput layer has 5 inputs.

• Range of values : non-negative float number

• Type : float

• Default value : 0

• Required : no

Inputs

• 1 : 2D input tensor with box logits with shape [N, num_prior_boxes \* num_loc_classes \* 4] and type T. num_loc_classes is equal to num_classes when share_location is 0 or it’s equal to 1 otherwise. Required.

• 2 : 2D input tensor with class predictions with shape [N, num_prior_boxes \* num_classes] and type T. Required.

• 3 : 3D input tensor with proposals with shape [priors_batch_size, 1, num_prior_boxes \* prior_box_size] or [priors_batch_size, 2, num_prior_boxes \* prior_box_size]. priors_batch_size is either 1 or N. Size of the second dimension depends on variance_encoded_in_target. If variance_encoded_in_target is equal to 0, the second dimension equals to 2 and variance values are provided for each boxes coordinates. If variance_encoded_in_target is equal to 1, the second dimension equals to 1 and this tensor contains proposals boxes only. prior_box_size is equal to 4 when normalized is set to 1 or it’s equal to 5 otherwise. Required.

• 4 : 2D input tensor with additional class predictions information described in the article. Its shape must be equal to [N, num_prior_boxes \* 2]. Optional.

• 5 : 2D input tensor with additional box predictions information described in the article. Its shape must be equal to first input tensor shape. Optional.

Outputs

• 1 : 4D output tensor with type T. Its shape depends on keep_top_k or top_k being set. It keep_top_k[0] is greater than zero, then the shape is [1, 1, N \* keep_top_k[0], 7]. If keep_top_k[0] is set to -1 and top_k is greater than zero, then the shape is [1, 1, N \* top_k \* num_classes, 7]. Otherwise, the output shape is equal to [1, 1, N \* num_classes \* num_prior_boxes, 7].

Types

• T : any supported floating-point type.

Example

<layer ... type="DetectionOutput" version="opset8">
<data background_label_id="1" code_type="caffe.PriorBoxParameter.CENTER_SIZE" confidence_threshold="0.019999999552965164" input_height="1" input_width="1" keep_top_k="200" nms_threshold="0.44999998807907104" normalized="true" share_location="true" top_k="200" variance_encoded_in_target="false" clip_after_nms="false" clip_before_nms="false" objectness_score="0" decrease_label_id="false"/>
<input>
<port id="0">
<dim>1</dim>
<dim>5376</dim>
</port>
<port id="1">
<dim>1</dim>
<dim>2688</dim>
</port>
<port id="2">
<dim>1</dim>
<dim>2</dim>
<dim>5376</dim>
</port>
</input>
<output>
<port id="3" precision="FP32">
<dim>1</dim>
<dim>1</dim>
<dim>200</dim>
<dim>7</dim>
</port>
</output>
</layer>