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NCS2 SSD Mobilenet v2 returns zeros



I'm trying to use the NCS2 with SSD Mobilenet v2 to detect objects. My problem is that when I use the converted model for detection, all I get is a DetectionOuput with shape [1,1,100,7] that consists of only zeros, except the first element which is -1. I get the same result for different example images.

I have tried 2 different models, both with the same result. I got the models from this page:

I used "SSD MobileNet V2 COCO" and "SSD Lite MobileNet V2 COCO". Since they are from the supported model zoo, I think the base models are not the problem.


This is how I convert the TensorFlow model to the IR:

 --input_shape [1,300,300,3] 
 --tensorflow_use_custom_operations_config ../../../model_optimizer/extensions/front/tf/ssd_v2_support.json 
 --tensorflow_object_detection_api_pipeline_config object_detection/common/ssd_mobilenet_v2_coco/tf/ssd_mobilenet_v2_coco_2018_03_29/pipeline.config 
 --data_type FP16 
 --input_model object_detection/common/ssd_mobilenet_v2_coco/tf/ssd_mobilenet_v2_coco_2018_03_29/frozen_inference_graph.pb 


This is the output I get when running the conversion command above:

Model Optimizer arguments:
Common parameters:
	- Path to the Input Model: 	/opt/intel/openvino_2019.2.242/deployment_tools/open_model_zoo/tools/downloader/object_detection/common/ssd_mobilenet_v2_coco/tf/ssd_mobilenet_v2_coco_2018_03_29/frozen_inference_graph.pb
	- Path for generated IR: 	/opt/intel/openvino_2019.2.242/deployment_tools/open_model_zoo/tools/downloader/.
	- IR output name: 	frozen_inference_graph
	- Log level: 	ERROR
	- Batch: 	Not specified, inherited from the model
	- Input layers: 	Not specified, inherited from the model
	- Output layers: 	detection_boxes,detection_scores,num_detections
	- Input shapes: 	[1,300,300,3]
	- Mean values: 	Not specified
	- Scale values: 	Not specified
	- Scale factor: 	Not specified
	- Precision of IR: 	FP16
	- Enable fusing: 	True
	- Enable grouped convolutions fusing: 	True
	- Move mean values to preprocess section: 	False
	- Reverse input channels: 	False
TensorFlow specific parameters:
	- Input model in text protobuf format: 	False
	- Path to model dump for TensorBoard: 	None
	- List of shared libraries with TensorFlow custom layers implementation: 	None
	- Update the configuration file with input/output node names: 	None
	- Use configuration file used to generate the model with Object Detection API: 	/opt/intel/openvino_2019.2.242/deployment_tools/open_model_zoo/tools/downloader/object_detection/common/ssd_mobilenet_v2_coco/tf/ssd_mobilenet_v2_coco_2018_03_29/pipeline.config
	- Operations to offload: 	None
	- Patterns to offload: 	None
	- Use the config file: 	/opt/intel/openvino_2019.2.242/deployment_tools/open_model_zoo/tools/downloader/../../../model_optimizer/extensions/front/tf/ssd_v2_support.json
Model Optimizer version: 	2019.2.0-436-gf5827d4
The Preprocessor block has been removed. Only nodes performing mean value subtraction and scaling (if applicable) are kept.

[ SUCCESS ] Generated IR model.
[ SUCCESS ] XML file: /opt/intel/openvino_2019.2.242/deployment_tools/open_model_zoo/tools/downloader/./frozen_inference_graph.xml
[ SUCCESS ] BIN file: /opt/intel/openvino_2019.2.242/deployment_tools/open_model_zoo/tools/downloader/./frozen_inference_graph.bin
[ SUCCESS ] Total execution time: 27.89 seconds. 


And this is a minimal code sample that reproduces the problem:

import cv2
import numpy as np
from openvino.inference_engine import IENetwork, IECore

model_xml = "./ssdlite_mobilenet_v2_coco_2018_05_09/mobilenetv2.xml"
model_bin = "./ssdlite_mobilenet_v2_coco_2018_05_09/mobilenetv2.bin"

ie = IECore()
net = IENetwork(model=model_xml, weights=model_bin)

input_blob = next(iter(net.inputs))
output_blob = next(iter(net.outputs))
net.batch_size = 1

n, c, h, w = net.inputs[input_blob].shape
print(n, c, h, w)

image = cv2.imread("dog.jpg")
img = cv2.resize(image, (w,h))

exec_net = ie.load_network(network=net, device_name="MYRIAD")
res = exec_net.infer(inputs={input_blob: np.reshape(img, [n,c,w,h])})


There is probably something wrong with the command or I'm not using the python API correctly. Any pointers would be appreciated.


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4 Replies

Dear mred,

Please try one of our SSD samples, like the Python object_detection_demo_ssd_async under demos ? Does it produce proper output ? Documentation for this demo sample is here.





Hello Shubha R.,

thank you for making me aware of the python demos, I didn't know about them before. Yes, the python demo produces proper output and while taking a look at the demo code, I found my error.

The demo preprocesses the frame like this:

in_frame = cv2.resize(frame, (w, h))
in_frame = in_frame.transpose((2, 0, 1))  # Change data layout from HWC to CHW
in_frame = in_frame.reshape((n, c, h, w))

In my own code, I did the resizing and reshaping, but not the transposing. After adding the line that changes the layout to CHW, the object detection is working now!

Thank you,



Dear mred,

I'm thrilled that the OpenVino demo helped to fix your mistake.

Thanks for using OpenVino !



Shubha R. (Intel) wrote:

Dear mred,

I'm thrilled that the OpenVino demo helped to fix your mistake.

Thanks for using OpenVino !


I'm confused, why could he get the right result although he  didn't set the "--reverse_input_channels" option.  When should I add this option? By the way, Must I set the "input_shape" option? It seems that the model works well although I did not do that.