Video

Video

Provides interface between the Qml type SVideo and python. So to communicate with SVideo in python you will have to use Video.

import statement

import soloman 2.2

Basic Usage

example.qml

import QtQuick 2.14
import QtQuick.Controls 2.14
import solomon 2.2

ApplicationWindow {
	visible: true
	width: 800
	height: 500

    SVideo {
        id: scr_01
        objectName: "scr_01"  // declare objectName to be used in python
    }
    
}

example.py

# -*- coding: utf-8 -*-
import sys
import cv2
import threading
from time import sleep

from PyQt5.QtGui import QGuiApplication
from PyQt5.QtQml QQmlApplicationEngine
import soloman

app = QGuiApplication(sys.argv)

# Create a QML engine.
engine = QQmlApplicationEngine()
engine.quit.connect(app.quit)
engine.load(QUrl('example.qml'))

# Get SVideo
vid = soloman.Video(engine)
vid.get_SVideo('scr_01')  # objectName goes here

# Capture
capture = cv2.VideoCapture(0)  # capture camera

def start_capt():
    # start thread
    o_thread = threading.Thread(target=_start_capt)
    o_thread.daemon = True
    o_thread.start()

def _start_capt():

    while True:

        ret, frame = capture.read()

        if not ret:
            break

        vid.show_frame(frame)
        sleep(1/24)

# Call to start capturing
start_capt()

# Run the app
ret_value = app.exec_()
capture.release()
sys.exit(0)

The above example uses the show_frame to display the frame. This is best for showing a capturing device like a camera. But for a video as OpenCV is capable of, this can but isn't very suitable for the job. Use update instead.

...
# Capture
capture = cv2.VideoCapture('mining.mp4')
...
def _start_capt():

    while True:
        ...
        vid.update(frame)
        sleep(1/40)  # use 40 just to be safe for 24 frames_per_second
...

It is also important you beef up your refresh rate for the update . It plays 24 frames per second. In case some other thing is running so that, your program runs slow, the update is not very patient, it is going to read that as an end of file. So a sleep function of exactly 0.042 seconds sleep(1/24), is fine, but unsafe, beef it up a little, like say 0.025 seconds sleep(1/40).

Methods

• _init_
• get_current_frame
• get_SVideo
• show_frame
• update

_init_

Does some initialization.

__init__(engine=None)

engine is the QmlEngine instance returned by calling either QmlEngine() or QQmlApplicationEngine()

It is called automatically when you create an instance of the class

vid = soloman.Video(QmlEngine)

get_current_frame

Gives you the current frame.

get_current_frame()

frame = solomon.Video(engine).get_SVideo('scr_01').get_current_frame()

frame is the filename of a temporary file, copy it to a location you can access later.

get_SVideo

Sets the corresponding handler for the SVideo Qml type so we can use to control it from python

get_SVideo(objectName)

objectName is the objectName declared in Qml like:

Svideo {
	objectName: "sv_01"
}

so it becomes:

vid = soloman.Video()
svid = vid.get_SVideo("sv_01")

show_frame

show_frame is like an instant update.

show_frame(frame)

frame is a numpy array, which is a datatype cv2.VideoCapture returns.

It is suitable for controlling your own frames per second. It is also less on system resources.

It is excellent for capturing devices.

cap = cv2.VideoCapture(0)  # capture the camera
while True:
    ret, frame = cap.read()
    solomon.Video(engine).get_SVideo('scr_01').show_frame(frame)
    sleep(1/24)

update

update is best suited for video analysis

update(frame)

frame is a numpy array, which is a datatype cv2.VideoCapture returns.

It is suitable for video analysis. It plays 24fps even if you supply it with more frames per each second, meaning it stores it in a list and plays it later. For that reason, if you supply it with less than 24 frames per second it reads that as an end-of-file and exits. When reading from a video file with cv2, please make sure the seconds you pass into the sleep function is below 0.025 seconds, i.e. sleep(1/40)

cap = cv2.VideoCapture('whether.mp4')  # capture from a video feed
while True:
    ret, frame = cap.read()
    solomon.Video(engine).get_SVideo('scr_01').update(frame)
    sleep(1/40)

Properties

N/A