ReIdentificationNet - NVIDIA Docs

ReIdentificationNet takes cropped images of a person from different perspectives as network input and outputs the embedding features for that person. The embeddings are used to perform similarity matching to re-identify the same person. The model supported in the current version is based on ResNet, which is the most commonly used baseline for re-identification due to its high accuracy.

Data Input for ReIdentificationNet

The ReIdentificationNet apps in TAO Toolkit expect data in Market-1501 format for training and evaluation.

See the Data Annotation Format page for more information about the Market-1501 data format.

Creating an Experiment Spec File

The spec file for ReIdentificationNet includes model, dataset, re_ranking, and train parameters. Here is an example spec for training a ResNet model on Market-1501 that contains 751 identities in the training set.

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            results_dir: "/path/to/experiment_results"
encryption_key: nvidia_tao
model:
  backbone: resnet_50
  last_stride: 1
  pretrain_choice: imagenet
  pretrained_model_path: "/path/to/pretrained_model.pth"
  input_channels: 3
  input_width: 128
  input_height: 256
  neck: bnneck
  feat_dim: 256
  neck_feat: after
  metric_loss_type: triplet
  with_center_loss: False
  with_flip_feature: False
  label_smooth: True
dataset:
  train_dataset_dir: "/path/to/train_dataset_dir"
  test_dataset_dir: "/path/to/test_dataset_dir"
  query_dataset_dir: "/path/to/query_dataset_dir"
  num_classes: 751
  batch_size: 64
  val_batch_size: 128
  num_workers: 1
  pixel_mean: [0.485, 0.456, 0.406]
  pixel_std: [0.226, 0.226, 0.226]
  padding: 10
  prob: 0.5
  re_prob: 0.5
  sampler: softmax_triplet
  num_instances: 4
re_ranking:
  re_ranking: True
  k1: 20
  k2: 6
  lambda_value: 0.3
train:
  results_dir: "${results_dir}/train"
  optim:
    name: Adam
    lr_monitor: val_loss
    steps: [40, 70]
    gamma: 0.1
    bias_lr_factor: 1
    weight_decay: 0.0005
    weight_decay_bias: 0.0005
    warmup_factor: 0.01
    warmup_iters: 10
    warmup_method: linear
    base_lr: 0.00035
    momentum: 0.9
    center_loss_weight: 0.0005
    center_lr: 0.5
    triplet_loss_margin: 0.3
  num_epochs: 120
  checkpoint_interval: 10

Parameter	Data Type	Default	Description
`model`	dict config	–	The configuration for the model architecture
`train`	dict config	–	The configuration for the training process
`dataset`	dict config	–	The configuration for the dataset
`re_ranking`	dict config	–	The configuration for the re-ranking module

model

The model parameter provides options to change the ReIdentificationNet architecture.

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            model:
  backbone: resnet_50
  last_stride: 1
  pretrain_choice: imagenet
  pretrained_model_path: "/path/to/pretrained_model.pth"
  input_channels: 3
  input_width: 128
  input_height: 256
  neck: bnneck
  feat_dim: 256
  neck_feat: after
  metric_loss_type: triplet
  with_center_loss: False
  with_flip_feature: False
  label_smooth: True

Parameter	Datatype	Default	Description	Supported Values
`backbone`	string	resnet_50	The type of model, which can be resnet_50 or a Swin-based architecture (refer to ReIdentificationNet Transformer for more details)	“resnet_50”, “swin_base_patch4_window7_224”, “swin_small_patch4_window7_224, “swin_tiny_patch4_window7_224”
`last_stride`	unsigned int	1	The number of strides during convolution	>0
`pretrain_choice`	string	imagenet	The pre-trained network	imagenet/self/””
`pretrained_model_path`	string		The path to the pre-trained model
`input_channels`	unsigned int	3	The number of input channels	>0
`input_width`	int	128	The width of the input images	>0
`input_height`	int	256	The height of the input images	>0
`neck`	string	bnneck	Specifies whether to train with BNNeck	bnneck/””
`feat_dim`	unsigned int	256	The output size of the feature embeddings	>0
`neck_feat`	string	after	Specifies which feature of BNNeck to use for testing	before/after
`metric_loss_type`	string	triplet	The type of metric loss	triplet/center/triplet_center
`with_center_loss`	bool	False	Specifies whether to enable center loss	True/False
`with_flip_feature`	bool	False	Specifies whether to enable image flipping	True/False
`label_smooth`	bool	True	Specifies whether to enable label smoothing	True/False

dataset

The dataset parameter defines the dataset source, training batch size, and augmentation.

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            dataset:
  train_dataset_dir: "/path/to/train_dataset_dir"
  test_dataset_dir: "/path/to/test_dataset_dir"
  query_dataset_dir: "/path/to/query_dataset_dir"
  num_classes: 751
  batch_size: 64
  val_batch_size: 128
  num_workers: 1
  pixel_mean: [0.485, 0.456, 0.406]
  pixel_std: [0.226, 0.226, 0.226]
  padding: 10
  prob: 0.5
  re_prob: 0.5
  sampler: softmax_triplet
  num_instances: 4

Parameter	Datatype	Default	Description	Supported Values
`train_dataset_dir`	string		The path to the train images
`test_dataset_dir`	string		The path to the test images
`query_dataset_dir`	string		The path to the query images
`num_classes`	unsigned int	751	The number of unique person IDs	>0
`batch_size`	unsigned int	64	The batch size for training	>0
`val_batch_size`	unsigned int	128	The batch size for validation	>0
`num_workers`	unsigned int	1	The number of parallel workers processing data	>0
`pixel_mean`	float list	[0.485, 0.456, 0.406]	The pixel mean for image normalization	float list
`pixel_std`	float list	[0.226, 0.226, 0.226]	The pixel standard deviation for image normalization	float list
`padding`	unsigned int	10	The pixel padding size around images for image augmentation	>=1
`prob`	float	0.5	The random horizontal flipping probability for image augmentation	>0
`re_prob`	float	0.5	The random erasing probability for image augmentation	>0
`sampler`	string	softmax_triplet	The type of sampler for data loading	softmax/triplet/softmax_triplet
`num_instances`	unsigned int	4	The number of image instances of the same person in a batch	>0

re_ranking

The re_ranking parameter defines the settings for the re-ranking module.

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            re_ranking:
  re_ranking: True
  k1: 20
  k2: 6
  lambda_value: 0.3

Parameter	Datatype	Default	Description	Supported Values
`re_ranking`	bool	True	A flag that enables the re-ranking module	True/False
`k1`	unsigned int	20	The k used for k-reciprocal nearest neighbors	>0
`k2`	unsigned int	6	The k used for local query expansion	>0
`lambda_value`	float	0.3	The weight of original distance in the combination with Jaccard distance	>0.0

train

The train parameter defines the hyperparameters of the training process.

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            train:
  optim:
    name: Adam
    lr_monitor: val_loss
    steps: [40, 70]
    gamma: 0.1
    bias_lr_factor: 1
    weight_decay: 0.0005
    weight_decay_bias: 0.0005
    warmup_factor: 0.01
    warmup_iters: 10
    warmup_method: linear
    base_lr: 0.00035
    momentum: 0.9
    center_loss_weight: 0.0005
    center_lr: 0.5
    triplet_loss_margin: 0.3
  num_epochs: 120
  checkpoint_interval: 10

Parameter	Datatype	Default	Description	Supported Values
`optim`	dict config		The configuration for the SGD optimizer, including the learning rate, learning scheduler, weight decay, etc.
`num_epochs`	unsigned int	120	The total number of epochs to run the experiment	>0
`checkpoint_interval`	unsigned int	10	The interval at which the checkpoints are saved	>0
`clip_grad_norm`	float	0.0	The amount to clip the gradient by the L2 norm. A value of 0.0 specifies no clipping.	>=0

optim

The optim parameter defines the config for the SGD optimizer in training, including the learning rate, learning scheduler, and weight decay.

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            optim:
  name: Adam
  lr_monitor: val_loss
  lr_steps: [40, 70]
  gamma: 0.1
  bias_lr_factor: 1
  weight_decay: 0.0005
  weight_decay_bias: 0.0005
  warmup_factor: 0.01
  warmup_iters: 10
  warmup_method: linear
  base_lr: 0.00035
  momentum: 0.9
  center_loss_weight: 0.0005
  center_lr: 0.5
  triplet_loss_margin: 0.3

Parameter	Datatype	Default	Description	Supported Values
`name`	string	Adam	The name of the optimizer	Adam/SGD/Adamax/…
`lr_monitor`	string	val_loss	The monitor value for the AutoReduce scheduler	val_loss/train_loss
`lr_steps`	int list	[40, 70]	The steps to decrease the learning rate for the `MultiStep` scheduler	int list
`gamma`	float	0.1	The decay rate for the WarmupMultiStepLR	>0.0
`bias_lr_factor`	float	1	The bias learning rate factor for the WarmupMultiStepLR	>=1
`weight_decay`	float	0.0005	The weight decay coefficient for the optimizer	>0.0
`weight_decay_bias`	float	0.0005	The weight decay bias for the optimizer	>0.0
`warmup_factor`	float	0.01	The warmup factor for the WarmupMultiStepLR scheduler	>0.0
`warmup_iters`	unsigned int	10	The number of warmup iterations for the WarmupMultiStepLR scheduler	>0
`warmup_method`	string	linear	The warmup method for the optimizer	linear/cosine
`base_lr`	float	0.00035	The initial learning rate for the training	>0.0
`momentum`	float	0.9	The momentum for the WarmupMultiStepLR optimizer	>0.0
`center_loss_weight`	float	0.0005	The balanced weight of center loss	>0.0
`center_lr`	float	0.5	The learning rate of SGD to learn the centers of center loss	>0.0
`triplet_loss_margin`	float	0.3	The margin value for triplet loss	>0.0

Training the Model

Use the following command to run ReIdentificationNet training:

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            tao model re_identification train -e <experiment_spec_file>
                            -r <results_dir>
                            -k <key>
                            [train.gpu_ids=<gpu id list>]

Required Arguments

-e, --experiment_spec_file: The path to the experiment spec file.
-r, --results_dir: The path to a folder where the experiment outputs should be written.
-k, --key: The user-specific encoding key to save or load a .tlt model.

Optional Arguments

train.gpu_ids: The GPU indices list for training. If you set more than one GPU ID, multi-GPU training will be triggered automatically.

Here’s an example of using the ReIdentificationNet training command:

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            tao model re_identification train -e $DEFAULT_SPEC -r $RESULTS_DIR -k $KEY

Evaluating the model

The evaluation metric of ReIdentificationNet is the mean average precision and ranked accuracy. The plots of sampled matches and the cumulative matching characteristic (CMC) curve can be obtained using the evaluate.output_sampled_matches_plot and evaluate.output_cmc_curve_plot parameters, respectively.

Use the following command to run ReIdentificationNet evaluation:

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            tao model re_identification evaluate -e <experiment_spec_file>
                               -r <results_dir>
                               -k <key>
                               evaluate.checkpoint=<model to be evaluated>
                               evaluate.output_sampled_matches_plot=<path to the output sampled matches plot>
                               evaluate.output_cmc_curve_plot=<path to the output CMC curve plot>
                               evaluate.test_dataset=<path to test data>
                               evaluate.query_dataset=<path to query data>
                               [evaluate.gpu_id=<gpu index>]

Required Arguments

-e, --experiment_spec_file: The experiment spec file to set up the evaluation experiment
-r, --results_dir: The path to a folder where the experiment outputs should be written
-k, --key: The encoding key for the .tlt model
evaluate.checkpoint: The .tlt model
evaluate.output_sampled_matches_plot: The path to the plotted file of sampled matches
evaluate.output_cmc_curve_plot: The path to the plotted file of the CMC curve
evaluate.test_dataset: The path to the test data
evaluate.query_dataset: The path to the query data

Optional Argument

evaluate.gpu_id: The GPU index used to run the evaluation. You can specify the GPU index used to run evaluation when the machine has multiple GPUs installed. Note that evaluation can only run on a single GPU.

Here’s an example of using the ReIdentificationNet evaluation command:

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            tao model re_identification evaluate -e $DEFAULT_SPEC -r $RESULTS_DIR -k $KEY evaluate.checkpoint=$TRAINED_TLT_MODEL evaluate.output_sampled_matches_plot=$OUTPUT_SAMPLED_MATCHED_PLOT evaluate.output_cmc_curve_plot=$OUTPUT_CMC_CURVE_PLOT evaluate.test_dataset=$TEST_DATA evaluate.query_dataset=$QUERY_DATA

Running Inference on the Model

Use the following command to run inference on ReIdentificationNet with the .tlt model.

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            tao model re_identification inference -e <experiment_spec>
                                -r <results_dir>
                                -k <key>
                                inference.checkpoint=<inference model>
                                inference.output_file=<path to output file>
                                inference.test_dataset=<path to gallery data>
                                inference.query_dataset=<path to query data>
                                [inference.gpu_id=<gpu index>]

The output will be a JSON file that contains the feature embeddings of all the test and query data.

Required Arguments

-e, --experiment_spec: The experiment spec file to set up inference
-r, --results_dir: The path to a folder where the experiment outputs should be written
-k, --key: The encoding key for the .tlt model
inference.checkpoint: The .tlt model to perform inference with
inference.output_file: The path to the output JSON file
inference.test_dataset: The path to the test data
inference.query_dataset: The path to the query data

Optional Argument

inference.gpu_id: The index of the GPU that will be used to run inference. You can specify this value when the machine has multiple GPUs installed. Note that inference can only run on a single GPU.

Here’s an example of using the ReIdentificationNet inference command:

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            tao model re_identification inference -e $DEFAULT_SPEC -r $RESULTS_DIR -k $KEY inference.checkpoint=$TRAINED_TLT_MODEL inference.output_file=$OUTPUT_FILE inference.test_dataset=$TEST_DATA inference.query_dataset=$QUERY_DATA

The expected output would be as follows:

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            [
  {
    "img_path": "/path/to/img1.jpg",
    "embedding": [-0.30, 0.12, 0.13,...]
  },
  {
    "img_path": "/path/to/img2.jpg",
    "embedding": [-0.10, -0.06, -1.85,...]
  },
  ...
  {
    "img_path": "/path/to/imgN.jpg",
    "embedding": [1.41, 0.63, -0.15,...]
  }
]

Exporting the Model

Use the following command to export ReIdentificationNet to .onnx format for deployment:

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            tao model re_identification export -e <experiment_spec>
                             -r <results_dir>
                             -k <key>
                             export.checkpoint=<tlt checkpoint to be exported>
                             [export.onnx_file=<path to exported file>]
                             [export.gpu_id=<gpu index>]

Required Arguments

-e, --experiment_spec: The experiment spec file to set up export.
-r, --results_dir: The path to a folder where the experiment outputs should be written.
-k, --key: The encoding key for the .tlt model.
export.checkpoint: The .tlt model to be exported.

Optional Arguments

export.onnx_file: The path to save the exported model to. The default path is in the same directory as the \*.tlt model.
export.gpu_id: The index of the GPU that will be used to run the export. You can specify this value when the machine has multiple GPUs installed. Note that export can only run on a single GPU.

Here’s an example of using the ReIdentificationNet export command:

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            tao model re_identification export -e $DEFAULT_SPEC -r $RESULTS_DIR -k $KEY export.checkpoint=$TRAINED_TLT_MODEL

Deploying the Model

You can deploy the trained deep -earning and computer-vision models on edge devices–such as a Jetson Xavier, Jetson Nano, or Tesla–or in the cloud with NVIDIA GPUs. The exported \*.onnx model can also be used with TAO Toolkit Triton Apps.

Running ReIdentificationNet Inference on the Triton Sample

The TAO Toolkit Triton Apps provide an inference sample for ReIdentificationNet. It consumes a TensorRT engine and supports running with a directory of query (probe) images and a directory of test (gallery) images containing the same identities.

To use this sample, you need to generate the TensorRT engine from an \*.onnx model using trtexec.

Generating TensorRT Engine Using `trtexec`

For instructions on generating a TensorRT engine using the trtexec command, refer to the trtexec guide for ReIdentificationNet.

Running the Triton Inference Sample

You can generate the TensorRT engine when starting the Triton server using the following command:

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            bash scripts/start_server.sh

When the server is running, you can get results from a directory of query images and a directory of test images using the following command with a client:

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            python tao_client.py <path_to_query_directory> \
                    --test_dir <path_to_test_directory>
                    -m re_identification_tao model \
                    -x 1 \
                    -b 16 \
                    --mode Re_identification \
                    -i https \
                    -u localhost:8000 \
                    --async \
                    --output_path <path_to_output_directory>

Note

The server will perform inference on the input image directories. The results are saved as a JSON file. The following is a sample of the JSON output:

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            [
  ...,
  {
    "img_path": "/localhome/Data/market1501/query/1121_c3s2_156744_00.jpg",
    "embedding": [-1.1530249118804932, -1.8521332740783691,..., 0.380886435508728]
  },...
  {
    "img_path": "/localhome/Data/market1501/bounding_box_test/1377_c2s3_038007_05.jpg",
    "embedding": [0.09496910870075226, 0.26107653975486755,..., 0.2835155725479126]
  },...
]

End-to-End Inference Using Triton

The TAO Toolkit Triton Apps provides a sample for end-to-end inference from a directory of query images and a directory of test images. The sample downloads the Market-1501 dataset and randomly samples a subset of 100 identities. The client implicitly converts the image samples into arrays and sends them to the Triton server. The feature embedding for each image is returned and saved to the JSON output. An image of sampled matches and a figure of the CMC curve is also generated for visualization.

You can start the Triton server using the following command (only the ReIdentificationNet model will be downloaded and converted into a TensorRT engine):

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            bash scripts/re_id_e2e_inference/start_server.sh

Once the Triton server has started, open another terminal and use the following command to run re-identification on the query and test images using the Triton server instance that you have previously spun up:

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            bash scripts/re_id_e2e_inference/start_client.sh