Human friendly video for linux
Project description
v4l2py
Video for linux 2 (V4L2) python library
A two purpose API:
- high level Device API for humans to play with :-)
- raw python binding for the v4l2 (video4linux2) userspace API, using ctypes (don't even bother wasting your time here. You probably won't use it)
Only works on python >= 3.7.
Installation
From within your favorite python environment:
$ pip install v4l2py
Usage
Without further ado:
>>> from v4l2py import Device
>>> with Device.from_id(0) as cam:
>>> for i, frame in enumerate(cam):
... print(f"frame #{i}: {len(frame)} bytes")
... if i > 9:
... break
...
frame #0: 54630 bytes
frame #1: 50184 bytes
frame #2: 44054 bytes
frame #3: 42822 bytes
frame #4: 42116 bytes
frame #5: 41868 bytes
frame #6: 41322 bytes
frame #7: 40896 bytes
frame #8: 40844 bytes
frame #9: 40714 bytes
frame #10: 40662 bytes
Getting information about the device:
>>> from v4l2py.device import Device, BufferType
>>> cam = Device.from_id(0)
>>> cam.open()
>>> cam.info.card
'Integrated_Webcam_HD: Integrate'
>>> cam.info.capabilities
<Capability.STREAMING|EXT_PIX_FORMAT|VIDEO_CAPTURE: 69206017>
>>> cam.info.formats
[ImageFormat(type=<BufferType.VIDEO_CAPTURE: 1>, description=b'Motion-JPEG',
flags=<ImageFormatFlag.COMPRESSED: 1>, pixelformat=<PixelFormat.MJPEG: 1196444237>),
ImageFormat(type=<BufferType.VIDEO_CAPTURE: 1>, description=b'YUYV 4:2:2',
flags=<ImageFormatFlag.0: 0>, pixelformat=<PixelFormat.YUYV: 1448695129>)]
>>> cam.get_format(BufferType.VIDEO_CAPTURE)
Format(width=640, height=480, pixelformat=<PixelFormat.MJPEG: 1196444237>}
>>> for ctrl in cam.controls.values(): print(ctrl)
<Control name=Brightness, type=INTEGER, min=0, max=255, step=1>
<Control name=Contrast, type=INTEGER, min=0, max=255, step=1>
<Control name=Saturation, type=INTEGER, min=0, max=100, step=1>
<Control name=Hue, type=INTEGER, min=-180, max=180, step=1>
<Control name=Gamma, type=INTEGER, min=90, max=150, step=1>
<Control name=White Balance Temperature, type=INTEGER, min=2800, max=6500, step=1>
<Control name=Sharpness, type=INTEGER, min=0, max=7, step=1>
<Control name=Backlight Compensation, type=INTEGER, min=0, max=2, step=1>
<Control name=Exposure (Absolute), type=INTEGER, min=4, max=1250, step=1>
asyncio
v4l2py is asyncio friendly:
$ python -m asyncio
>>> from v4l2py import Device
>>> with Device.from_id(0) as camera:
... async for frame in camera:
... print(f"frame {len(frame)}")
frame 10224
frame 10304
frame 10224
frame 10136
...
(check examples/basic_async.py)
gevent
v4l2py is also gevent friendly:
$ python
>>> from v4l2py import Device, GeventIO
>>> with Device.from_id(0, io=GeventIO) as camera:
... for frame in camera:
... print(f"frame {len(frame)}")
frame 10224
frame 10304
frame 10224
frame 10136
...
(check examples/basic_gevent.py and examples/web/app.py)
Bonus track
You've been patient enough to read until here so, just for you, a 20 line gem: a flask web server displaying your device on the web:
$ pip install flask
# web.py
import flask
from v4l2py import Device
app = flask.Flask('basic-web-cam')
def gen_frames():
with Device.from_id(0) as cam:
for frame in cam:
yield b"--frame\r\nContent-Type: image/jpeg\r\n\r\n" + frame.data + b"\r\n"
@app.route("/")
def index():
return '<html><img src="/stream" /></html>'
@app.route("/stream")
def stream():
return flask.Response(
gen_frames(), mimetype='multipart/x-mixed-replace; boundary=frame')
run with:
$ FLASK_APP=web flask run -h 0.0.0.0
Point your browser to 127.0.0.1:5000 and you should see your camera rolling!
Migrating from 1.x to 2
A frame changed from a simple bytes object to a Frame which contains the data plus all frame metadata.
As a consequence, when migrating from 1.x to 2, you will need to cast
frame object with bytes or access the frame.data item:
Before:
with Device.from_id(0) as cam:
for frame in cam:
buff = io.BytesIO(frame)
Now:
with Device.from_id(0) as cam:
for frame in cam:
frame = bytes(frame) # or frame = frame.data
buff = io.BytesIO(frame)
References
See the linux/videodev2.h header file for details.
Video for Linux Two Specification <http://linuxtv.org/downloads/v4l-dvb-apis/ch07s02.html>
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