在Nvidia Jetson Nano上利用YOLO进行目标检测的实践过程

硬件

Nvidia Jetson Nano

  Nvidia Jetson Nano是英伟达推出的深度学习开发板，性价比极高。本人也用过其他国产的深度学习开发板，比如某为的开发套件，难用的一批。Nvidia Jetson Nano上手及其容易，只要是有深度学习基础的人用起来和普通计算机一样，当然CPU的架构不同。但是所有深度学习代码都能在这上面跑，但是需要注意Nano的内存只有4G，性能并不是很好。

[官方Jetson Nano Developer Kit地址]
[Nvidia Jetson Nano官方镜像百度网盘下载地址] ❗ 提取码：sa5e ❗

  官方的Nano镜像包含了CUDA10.1和OpenCV，其他的环境需要自己配置。另外并不建议Nano更换为国内源，国内并没有很好的Arm架构Ubuntu源。

软件

要求

①识别类别2类：人和车(汽车、卡车等)。
②轻量化网络：在Nvidia Jetson Nano可以运行。
③当FPS减小时尽量提高网络精度。

网络结构可视化工具推荐

   Netron是神经网络、深度学习和机器学习模型的可视化工具。Netron支持ONNX (.onnx, .pb, .pbtxt), Keras (.h5, .keras), Core ML (.mlmodel), Caffe (.caffemodel, .prototxt), Caffe2 (predict_net.pb, predict_net.pbtxt), MXNet (.model, -symbol.json), TorchScript (.pt, .pth), NCNN (.param) and TensorFlow Lite (.tflite)。Netron在实验上支持 PyTorch (.pt, .pth), Torch (.t7), CNTK (.model, .cntk), Deeplearning4j (.zip), PaddlePaddle (.zip, model), Darknet (.cfg), MNN (.mnn), scikit-learn (.pkl), ML.NET (.zip), TensorFlow.js (model.json, .pb) and TensorFlow (.pb, .meta, .pbtxt).

[Netron在线网络结构可视化工具]
[Netron网络结构可视化工具下载地址]

YOLO

[YOLO系列官方主页]
[YOLO：You Only Look Once系列的学习]
[轻量化卷积神经网络]

  Nano很适合跑YOLO，不需要安装其他的深度学习框架，Nano上因为性能的限制不可能跑训练，所以建议在服务器上预先训练好网络，再在Nano上测试。所以我选择重新训练网络，首先是数据集，保留人和车类别，修改网络结构。

  以下是目前取得的结果：

name	Characteristic	AP(0.5)	AR(0.5:0.95)	Time	FPS(ON Nano)	cfg	weights	model structure	test result*
baseline	基于官方YOLOv3_tiny的修改	0.532	0.338	76S	10.0~11.0	[cfg]	[weights]	[svg]	[coco.json]
muti_conv	多维卷积	0.603	0.386	140S	5.8~6.5	[cfg]	[weights]	[svg]	[coco.json]
deep*	深层网络，计算量稍大	0.753	0.508	394S	1.9 ~ 2.0	[cfg] oymg	[weights] itpz	[svg]	[coco.json]
deep_prune*	深层网络的模型剪枝	0.720	0.479	273S	2.9~3.1	[cfg]	[weights]	[svg]	[coco.json]

表中*注释的位置，23486_images是COCO2014的Val数据集经过处理的总数(仅包含人和各种车的类别)，test result是此数据集的测试结果。deep网络结构参考自 [SlimYOLOv3] ，deep_prune参考自 [YOLOv3-model-pruning] ，测试的配置是RTX 2070。

具体步骤

baseline

  在yolov3-tiny.cfg文件中，通过查找[yolo]，找到网络结构的两个yolo层，

[yolo]
mask = 0,1,2
anchors = 10,14,  23,27,  37,58,  81,82,  135,169,  344,319
classes=80
num=6
jitter=.3
ignore_thresh = .7
truth_thresh = 1
random=1

将其中的classes=80改为classes=2。注意这里还需要改两个地方，2个[yolo]结构前面的[convolutional]层的通道数需要修改：$$filters=3\times (classes+5)$$也就是filters=21。

训练

运行：

./darknet detector train cfg/coco.data cfg/yolov3-tiny.cfg darknet53.conv.74

如果需要记录训练过程可以运行：

./darknet detector train cfg/coco.data cfg/yolov3-tiny.cfg darknet53.conv.74 >> train.txt

这样会记录下运行的过程但是不会在terminal中打印。
如果继续训练运行：

./darknet detector train cfg/coco.data cfg/yolov3-tiny.cfg backup/yolov3-tiny.backup

训练完成后会在backup文件夹中生成yolov3-tiny_final.weights文件。

测试

  此测试只在COCO2014Val数据集上进行测试，本人未找到任何COCO2014Test数据集的标签数据。运行：

./darknet detector valid cfg/coco.data cfg/yolov3-tiny.cfg backup/yolov3-tiny_final.weights

运行结束后会在results文件夹下生成coco_results.json文件，并打印出：

Total Detection Time: 76.561128 Seconds

  运行[coco_eval.py]。注意需要修改coco_eval.py文件中cocoGt_file、cocoDt_file的路径分别为下载的label.json路径和运行生成的coco_results.json文件。运行后会打印：

loading annotations into memory...
Done (t=1.45s)
creating index...
index created!
23443
Loading and preparing results...
DONE (t=2.25s)
creating index...
index created!
Running per image evaluation...
Evaluate annotation type *bbox*
DONE (t=22.27s).
Accumulating evaluation results...
DONE (t=1.07s).
 Average Precision  (AP) @[ IoU=0.50:0.95 | area=   all | maxDets=100 ] = 0.249
 Average Precision  (AP) @[ IoU=0.50      | area=   all | maxDets=100 ] = 0.532
 Average Precision  (AP) @[ IoU=0.75      | area=   all | maxDets=100 ] = 0.208
 Average Precision  (AP) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = 0.057
 Average Precision  (AP) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.292
 Average Precision  (AP) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.482
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets=  1 ] = 0.127
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets= 10 ] = 0.299
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets=100 ] = 0.338
 Average Recall     (AR) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = 0.137
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.401
 Average Recall     (AR) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.579

应用

muti_conv

  下载muti_conv的cfg文件，与baseline训练方法相同将yolov3-tiny.cfg改为muti_conv.cfg。
  muti_conv的网络结构是受到[MixNet]的启发，对浅层的特征进行多维卷积提取，如下图所示：

  在原先yolov3-tiny中，只有3×3的卷积核，这里我引入了多维卷积核：3×3、5×5、7×7和9×9四种。并在之后结合更多维的特征。经过长时间的训练和测试后得到：

Total Detection Time: 140.834962 Seconds
loading annotations into memory...
Done (t=1.50s)
creating index...
index created!
23475
Loading and preparing results...
DONE (t=3.22s)
creating index...
index created!
Running per image evaluation...
Evaluate annotation type *bbox*
DONE (t=26.13s).
Accumulating evaluation results...
DONE (t=1.26s).
 Average Precision  (AP) @[ IoU=0.50:0.95 | area=   all | maxDets=100 ] = 0.301
 Average Precision  (AP) @[ IoU=0.50      | area=   all | maxDets=100 ] = 0.603
 Average Precision  (AP) @[ IoU=0.75      | area=   all | maxDets=100 ] = 0.268
 Average Precision  (AP) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = 0.093
 Average Precision  (AP) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.354
 Average Precision  (AP) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.548
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets=  1 ] = 0.142
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets= 10 ] = 0.342
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets=100 ] = 0.386
 Average Recall     (AR) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = 0.170
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.455
 Average Recall     (AR) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.643

应用

deep

  deep网络的结构是参考了 [SlimYOLOv3] ，SlimYOLOv3是从YOLOv3-spp上经过模型剪枝得到，YOLOv3-spp由于计算量大、内存需求大不能在Nano上运行，但是SlimYOLOv3可以在Nano上以1.9 ~ 2.0帧/秒运行，极大的保证了准确率。SlimYOLOv3中采用了大量的残差模块，如下图所示：

  不断的加深残差结构的数量保证了网络性能更好，经过训练和测试得到：

Total Detection Time: 394.622764 Seconds
loading annotations into memory...
Done (t=1.79s)
creating index...
index created!
23486
Loading and preparing results...
DONE (t=2.90s)
creating index...
index created!
Running per image evaluation...
Evaluate annotation type *bbox*
DONE (t=119.78s).
Accumulating evaluation results...
DONE (t=5.71s).
 Average Precision  (AP) @[ IoU=0.50:0.95 | area=   all | maxDets=100 ] = 0.425
 Average Precision  (AP) @[ IoU=0.50      | area=   all | maxDets=100 ] = 0.754
 Average Precision  (AP) @[ IoU=0.75      | area=   all | maxDets=100 ] = 0.426
 Average Precision  (AP) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = 0.225
 Average Precision  (AP) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.488
 Average Precision  (AP) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.632
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets=  1 ] = 0.166
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets= 10 ] = 0.445
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets=100 ] = 0.508
 Average Recall     (AR) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = 0.341
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.567
 Average Recall     (AR) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.699

应用

deep_prune

  deep_prune网络的结构是参考自 [YOLOv3-model-pruning]。其相当于是对于deep网络的剪枝，网络深度和特征通道数减少，以至于其在Nano可以2.9~3.1帧/秒运行。

pythonTotal Detection Time: 273.457744 Seconds
loading annotations into memory...
Done (t=1.45s)
creating index...
index created!
23469
Loading and preparing results...
DONE (t=2.58s)
creating index...
index created!
Running per image evaluation...
Evaluate annotation type *bbox*
DONE (t=110.36s).
Accumulating evaluation results...
DONE (t=5.37s).
 Average Precision  (AP) @[ IoU=0.50:0.95 | area=   all | maxDets=100 ] = 0.398
 Average Precision  (AP) @[ IoU=0.50      | area=   all | maxDets=100 ] = 0.720
 Average Precision  (AP) @[ IoU=0.75      | area=   all | maxDets=100 ] = 0.393
 Average Precision  (AP) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = 0.183
 Average Precision  (AP) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.454
 Average Precision  (AP) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.637
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets=  1 ] = 0.164
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets= 10 ] = 0.424
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets=100 ] = 0.479
 Average Recall     (AR) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = 0.292
 Average Recall     (AR) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.537
 Average Recall     (AR) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.705

应用

传送门
  [目标检测]
  [YOLO：You Only Look Once系列的学习]
  [在Nvidia Jetson Nano上利用YOLO进行目标检测的实践过程]