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MaixPy Video Stream JPEG Streaming / Sending Images to Server
date author version content
2024-04-03
neucrack
1.0.0
Initial document
date author version content
2024-05-20
lxowalle
1.0.1
update JPEG-HTTP usage

Introduction

Sometimes it is necessary to send images to a server, or to push video from a webcam to a server, so here are two ways to do it.

  • One of the simplest methods is to compress images into JPEG format and send them one by one to the server. Note, this is a very basic method and not a formal way to stream video. It is also not suitable for high-resolution, high-frame-rate video streams, as it involves sending images one by one. For more efficient video streaming, please use the RTSP or RTMP modules discussed later.

  • Set up an HTTP server, so that the PC side can be accessed directly through the browser.

Methods for pushing streams as a client

from maix import image
import requests

# create image
img = image.Image(640, 480, image.Format.FMT_RGB)
# draw something
img.draw_rect(60, 60, 80, 80, image.Color.from_rgb(255, 0, 0))

# convert to jpeg
jpeg = img.to_format(image.Format.FMT_JPEG) # image.Format.FMT_PNG
# get jpeg bytes
jpeg_bytes = jpeg.to_bytes()

# faster way, borrow memory from jpeg object,
# but be careful, when jpeg object is deleted, jpeg_bytes object MUST NOT be used, or program will crash
# jpeg_bytes = jpeg.to_bytes(copy = False)

# send image binary bytes to server
url = "http://192.168.0.123:8080/upload"
res = requests.post(url, data=jpeg_bytes)
print(res.status_code)
print(res.text)

As you can see, the image is first converted into JPEG format, and then the binary data of the JPEG image is sent to the server via TCP.

Methods for pushing streams as a server

from maix import camera, time, app, http

html = """<!DOCTYPE html>
<html>
<head>
    <title>JPG Stream</title>
</head>
<body>
    <h1>MaixPy JPG Stream</h1>
    <img src="/stream" alt="Stream">
</body>
</html>"""

cam = camera.Camera(320, 240)
stream = http.JpegStreamer()
stream.set_html(html)
stream.start()

print("http://{}:{}".format(stream.host(), stream.port()))
while not app.need_exit():
    t = time.time_ms()
    img = cam.read()
    jpg = img.to_jpeg()
    stream.write(jpg)
    print(f"time: {time.time_ms() - t}ms, fps: {1000 / (time.time_ms() - t)}")

Steps:

  1. Import the image, camera and http modules:

    from maix import image, camera, http

  2. Initialize the camera:

    cam = camera.Camera(320, 240)

  3. Initialize Stream Object

    stream = http.JpegStreamer()
stream.start()
    • http.JpegStreamer() is used to create a JpegStreamer object, which will start an http server that will be used to publish jpeg image streams to clients.
    • stream.start() is used to start the http server.

  4. Custom html styles (optional)

    html = """<!DOCTYPE html>
<html>
<head>
    <title>JPG Stream</title>
</head>
<body>
    <h1>MaixPy JPG Stream</h1>
    <img src="/stream" alt="Stream">
</body>
</html>"""

stream.set_html(html)
    • html = xxx is the html code that can be used to customise the style of your web page. Note that the core code is <img src=‘/stream’ alt=‘Stream’>, be sure not to miss this line of code.
    • stream.set_html(html) is used to set the custom html code, this step is optional. The default browsing address is http://device_ip:8000.

  5. Getting images from the camera and pushing streams

    while 1:
    img = cam.read()
    jpg = img.to_jpeg()
    stream.write(jpg)
    • img = cam.read() gets an image from the camera, when initialised as cam = camera.Camera(320, 240) the img object is an RGB image with a resolution of 320x240.
    • jpg = img.to_jpeg() converts the image to jpeg format
    • stream.write(jpg) writes the image format to the server and the http server will send this image to the http client.
    1. Done, after running the code above, you can see the video stream directly through your browser, the default address is http://device_ip:8000. Open your browser and take a look!