minimal-ml-inference

Copyright (C) 2022, Axis Communications AB, Lund, Sweden. All Rights Reserved.

A minimal, machine learning inference application

This example demonstrates how to create a simple Python application that performs inference on the camera image.

Overview

This example composes three different container images into an application that performs an inference using a deep learning model.

The first container contains the actual program built in this example. It then uses gRPC/protobuf to call the second container, the inference-server, that is used to capture images from the camera and perform the actual inference by implementing the TensorFlow Serving API. You can find more documentation on the Machine Learning API documentation page. This example uses a containerized version of the ACAP Runtime as the inference-server.

Lastly, there is a third container that holds the deep learning model, which is put into a volume that is accessible by the other two images. The layout of the Docker image containing the model is shown below. The MODEL_PATH variable in the configuration file you're using specifies what model to use.

model
├── ssdlite-mobilenet-v2 - TFLite model
└── objects.txt - list of object labels

Example structure

Following are the list of files and a brief description of each file in the example

minimal-ml-inference
├── config
│   ├── env.aarch64.artpec8
│   └── env.aarch64.cpu
├── simple_inference.py
├── Dockerfile
├── Dockerfile.model
├── docker-compose.yml
└── README.md

• config/* - Environment configuration files
• simple_inference.py - A Python script that captures an image and send an inference call to the model server
• Dockerfile - Build instructions for the application image that is run on the camera
• Dockerfile.model - Build instructions for the inference model
• docker-compose.yml - A docker-compose file that specifies how the application is run (mounts, environment variables, etc.,)

Requirements

Meet the following requirements to ensure compatibility with the example:

• Axis device
  • Chip: ARTPEC-8 DLPU devices (e.g., Q1656)
  • Firmware: 11.10 or higher
  • Docker ACAP version 3.0 installed and started, using TLS with TCP and IPC socket and SD card as storage
• Computer
  • Either Docker Desktop version 4.11.1 or higher,
  • or Docker Engine version 20.10.17 or higher with BuildKit enabled using Docker Compose version 1.29.2 or higher

How to run the code

Build the Docker images

Define and export the application image name in APP_NAME and the model image name in MODEL_NAME for use in the Docker Compose file. Define and export also the CHIP parameter to be used during the build to select the right manifest file.

export APP_NAME=acap4-minimal-ml-inference
export MODEL_NAME=acap-dl-models
export CHIP=artpec8 # Valid options are 'artpec8' (hardware accelerator) or 'cpu'

# Install qemu to allow build for a different architecture
docker run --rm --privileged multiarch/qemu-user-static --credential yes --persistent yes

# Build application image
docker build --tag $APP_NAME .

# Build inference model image
docker build --file Dockerfile.model --tag $MODEL_NAME .

Set your device IP address and clear Docker memory

DEVICE_IP=<actual camera IP address>
DOCKER_PORT=2376

docker --tlsverify --host tcp://$DEVICE_IP:$DOCKER_PORT system prune --all --force

If you encounter any TLS related issues, please see the TLS setup chapter regarding the DOCKER_CERT_PATH environment variable in the Docker ACAP repository.

Install the images

Browse to the application page of the Axis device:

http://<AXIS_DEVICE_IP>/index.html#apps

Click on the tab Apps in the device GUI and enable Allow unsigned apps toggle.

Next, the built images needs to be uploaded to the device. This can be done through a registry or directly. In this case, the direct transfer is used by piping the compressed application directly to the device's Docker client:

docker save $APP_NAME | docker --tlsverify --host tcp://$DEVICE_IP:$DOCKER_PORT load

docker save $MODEL_NAME | docker --tlsverify --host tcp://$DEVICE_IP:$DOCKER_PORT load

Note

If the inference-server (containerized ACAP Runtime) is not already present on the device, it will be pulled from Docker Hub when running docker compose up. If the pull action fails due to network connectivity, pull the image to your host system and load it to the device instead.

Run the containers

With the application image on the device, it can be started using docker-compose.yml:

docker --tlsverify --host tcp://$DEVICE_IP:$DOCKER_PORT compose --env-file ./config/env.aarch64.$CHIP up

# Terminate with Ctrl-C and cleanup
docker --tlsverify --host tcp://$DEVICE_IP:$DOCKER_PORT compose --env-file ./config/env.aarch64.$CHIP down --volumes

The expected output from the application is the raw predictions from the model specified in the environment variable.

Hardware acceleration

The ./config folder contains configuration files with the parameters to run the inference on different camera models, also giving the possibility to use the hardware accelerator. To achieve the best performance we recommend using DLPU (Deep Learning Processing Unit) equipped ARTPEC-8 cameras. See ACAP Computer Vision SDK hardware and compatibility

License

Apache License 2.0