Artificial Intelligence with Tensorflow is a standard for image intelligent recognition industry. Even if examples are available to use Raspberry PI with tensorflow, all of these work only if an HDMI cable is connected to a monitor. Image classification video streaming from headless Raspberry PI is also possible with a few code edits
In this tutorial I’m going to show how to get image classification video streaming from headless (Lite) Raspberry PI installation with TensorFlow Lite.
With Tensorflow spreading in Artificial Intelligence applications and becoming more and more used in this industry, developers from all the world have adapted this open source framework to run on quite every device. A relatively new brunch merged from original one, adapting this framework to small devices using ARM processors. This is the case of IoT devices, smartphones and… Raspberry PIs. A lighter version of TensorFlow was born: TensorFlow Lite.
With Raspberry PI, new examples have been published on GitHub, the most significant being https://github.com/tensorflow/examples/tree/master/lite/examples/image_classification/raspberry_pi. But I wasn’t able to find tutorials explaining how to get it working on headless installation. I think this is based on the fact that they used one of most common PI camera python frameworks: “picamera”. Default usage includes preview function, which should require an HDMI cable connected. This means a Desktop installation that wastes Raspberry PI computing resources for desktop environment when not used.
In Picamera basic examples, on the other hand, network streaming is realized with start_recording function.
So, I decided to try in changing tensorflow image classification scrtipt, introducing socket management and streaming video over network. result is described in this guide.
In this tutorial I’m going to use a Raspberry PI 3 model A+, but it applies to all Raspberry PI boards able to run TensorFlow lite.
What We Need
As usual, I suggest adding from now to your favourite e-commerce shopping cart all needed hardware, so that at the end you will be able to evaluate overall costs and decide if continue with the project or remove them from the shopping cart. So, hardware will be only:
- Raspberry PI 3 Model A+ (including proper power supply or using a smartphone micro usb charger with at least 3A) or newer Raspberry PI Board
- high speed micro SD card (at least 16 GB, at least class 10)
- Raspberry PI Camera
Check hardware prices with following links:
Prepare Operating System
Start with your OS. You can use install Raspberry PI OS Lite guide (for headless, fast operating system). This tutorial is based, of course, on headless installation but, if you prefer, you can also use this guide with Raspberry PI OS Desktop (in this case working from its internal terminal).
Make your OS up to date. From terminal:
sudo apt update -y && sudo apt upgrade -y
Connect your camera module to Raspberry PI and enable camera from raspi-config tool. From terminal:
Terminal will show following page:
Go to option 3 (Interface Option) and press ENTER:
Select fist option (Camera) and press ENTER. In next screen move selectio from “No” to “Yes”:
Press ENTER and confirm also in following screen.
You wil go back to raspi-config home. Move to finish button and press ENTER.
This operation will require a reboot. Confirm in next screen and wait for reboot:
Once your Raspberry PI is rebooted, connect again to terminal and install required libraries. A note: numpy coming from pip3 repository is not compatible with current python3 default version from apt (3.7). For this reason we need to be sure that numpy from pip is uninstalled and get it from apt. This makes our versions a bit older, but we get a simpler way to install requirements. If you prefer to use last versions, you need to get all required packages from source. From terminal:
sudo apt install python3-pip git pip3 uninstall numpy pip3 install image sudo apt install python3-numpy libopenjp2-7-dev libtiff5
Use pip to install tensowflow lite. Link to .whl installation file are available from https://www.tensorflow.org/lite/guide/python?hl=en and depends on hardware and OS. With Raspberry PI OS (32 bit), at the time of this article installation will be done with this terminal command:
pip3 install https://github.com/google-coral/pycoral/releases/download/release-frogfish/tflite_runtime-2.5.0-cp37-cp37m-linux_armv7l.whl
Create a folder where files will be stored:
mkdir imclassif cd imclassif
Get raw requirements file and download script from github source portal:
wget https://raw.githubusercontent.com/tensorflow/examples/master/lite/examples/image_classification/raspberry_pi/requirements.txt wget https://raw.githubusercontent.com/tensorflow/examples/master/lite/examples/image_classification/raspberry_pi/download.sh
Get modified classify script from my download area:
From terminal, download pretrained models and labels:
bash download.sh ./
Run classify script with following command:
python3 peppe8o_classify.py --model mobilenet_v1_1.0_224_quant.tflite --label labels_mobilenet_quant_v1_224.txt
Raspberry PI will start listening on port 8000 for imcoming connections. You will be able to stop this process with common interrupt keys (CTRL+C).
That’s all on remote RPI. Now switch on local computer where you want to get image classification video stream.
Receiving Image Classification Streaming
I will use VLC media player, but you can use whatever media player able to manager network streams with h264 format.
Open VLC interface:
From “Media” menu use “Open Network stream” option:
Switch to “Network” tab and use your Raspberry PI IP address (mine one is 192.168.1.177) to set stream connection string. Compose URL with “tcp/h264://” + your RPI address + “:8000”. You shold use something similar to following:
You will get a result similar to following one:
What’s New Compared to Image Classification Original Code
Comparing to original code, I had to make some changed on code to stream video flow.
I added socket library to manage socket connection:
I also added socket management code in main block. This part opens a socket connection binding for every connection coming to Raspberry PI on port 8000 (please refer to picamera basic recipes page). setsockopt manages script interruption and re-execution after a few time: because of a intended behaviour, socket library keeps occuped connection for several seconds after script execution, so giving “address already in use” error if you try before this timeout. With “setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)” you can reuse address and port without waiting for resources to be free:
server_socket = socket.socket() server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) server_socket.bind(('0.0.0.0', 8000)) server_socket.listen(0) connection = server_socket.accept().makefile('wb')
Instead of start_preview function, I use start_recording according to picamera network streaming docs:
I prefer managing script interruprion with KeyboardInterrup exception instead of “finally”. This block stops camera and closes connection socket.
except KeyboardInterrupt: camera.stop_recording() connection.close()
This tutorial uses pre-trained model from tensowrflox examples. While this can be a good start, you will need to train your own model to get more accurate results.
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