fourcc = cv2.VideoWriter_fourcc(*'MJPG')实现什么功能
时间: 2024-09-25 13:21:02 浏览: 31
`cv2.VideoWriter_fourcc(*'MJPG')`是OpenCV (Computer Vision Library) 中的一个函数,用于创建VideoWriter对象时指定视频编码格式。这里的`fourcc`代表四字符代码(Four Character Code),是一种标准方法来表示视频编码类型。`*'MJPG'`是一个元组解包,其中`MJPEG`是 Motion JPEG 的缩写,这是一种常用的视频压缩格式,常用于实时视频传输和存储,因为它的压缩效率相对较高,同时保持一定的图像质量。
当你将`cv2.VideoWriter_fourcc(*'MJPG')`作为参数传递给`cv2.VideoWriter()`函数,例如:
```python
out = cv2.VideoWriter('output.mp4', cv2.VideoWriter_fourcc(*'MJPG'), fps, frame_size)
```
这里,`fps`是帧率(每秒帧数),`frame_size`是每一帧的尺寸,这样你就创建了一个能够以MJPEG格式写入视频的输出流。你可以使用这个`out`对象来写入每一帧的图像数据。
相关问题
import sys import cv2 from showPic import Ui_MainWindow from PyQt5 import QtGui from PyQt5.QtCore import * from PyQt5.QtGui import * from PyQt5.QtWidgets import * class videoShow(QMainWindow,Ui_MainWindow): def __init__(self): super().__init__() self.setupUi(self) @pyqtSlot() def on_pushButton_record_clicked(self): camera_path = 0 # 0:自带摄像头 1:外接摄像头 "xxx.mp4" "rtsp://admin:pwd@192.168.2.10/cam/..." capture = cv2.VideoCapture(camera_path) # 初始化播放器 流媒体 fourcc = cv2.VideoWriter_fourcc('M', 'P', '4', 'V') # XVID/DIVX MPEG MJPG X264 video_writer = cv2.VideoWriter("image/myself.mp4", fourcc, 25, (960, 540)) # 存放路径、、帧率fps、尺寸(且保证下面的frame也是这个尺寸) while True: flag, frame = capture.read() if flag is False: continue frame = cv2.resize(frame, (960, 540)) video_writer.write(frame) self.display_image(frame, self.label) # 显示帧到标签 key = cv2.waitKey(25) if key == 27: video_writer.release() break @pyqtSlot() def on_pushButton_play_clicked(self): video_path = "image/myself.mp4" # 已经录制好的视频路径 capture = cv2.VideoCapture(video_path) # 初始化播放器 while True: flag, frame = capture.read() if flag is False: break self.display_image(frame, self.label) # 显示帧到标签 key = cv2.waitKey(25) if key == 27: break capture.release() def display_image(self, frame, label): pic_image = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB) # 将BGR格式图像转换成RGB height, width = pic_image.shape[:2] pixMap = QImage(pic_image.data, width, height, width * 3, QImage.Format_RGB888) # 将RGB格式图像转换为八位图 pixMap = QPixmap.fromImage(pixMap) ratio = max(width / self.label.width(), height / self.label.height()) pixMap.setDevicePixelRatio(ratio) # 根据图片比例显示 self.label.setAlignment(Qt.AlignCenter) # 设置居中 self.label.setPixmap(pixMap) if __name__ == '__main__': app = QApplication(sys.argv) ui = videoShow() ui.show() sys.exit(app.exec_())修改这段代码,实现点击按钮停止录制以及保存视频
你可以在 `videoShow` 类中添加一个标志位 `recording` 来控制录制的开始和停止。同时,在停止录制时保存视频。以下是修改后的代码示例:
```python
import sys
import cv2
from showPic import Ui_MainWindow
from PyQt5 import QtGui
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
class videoShow(QMainWindow, Ui_MainWindow):
def __init__(self):
super().__init__()
self.setupUi(self)
self.recording = False
@pyqtSlot()
def on_pushButton_record_clicked(self):
if self.recording:
self.recording = False
self.pushButton_record.setText('开始录制')
self.video_writer.release() # 释放视频写入对象
else:
self.recording = True
self.pushButton_record.setText('停止录制')
camera_path = 0 # 0:自带摄像头 1:外接摄像头 "xxx.mp4" "rtsp://admin:pwd@192.168.2.10/cam/..."
capture = cv2.VideoCapture(camera_path) # 初始化播放器 流媒体
fourcc = cv2.VideoWriter_fourcc('M', 'P', '4', 'V') # XVID/DIVX MPEG MJPG X264
self.video_writer = cv2.VideoWriter("image/myself.mp4", fourcc, 25, (960, 540)) # 存放路径、、帧率fps、尺寸(且保证下面的frame也是这个尺寸)
while self.recording:
flag, frame = capture.read()
if flag is False:
continue
frame = cv2.resize(frame, (960, 540))
self.video_writer.write(frame)
self.display_image(frame, self.label) # 显示帧到标签
key = cv2.waitKey(25)
if key == 27:
break
@pyqtSlot()
def on_pushButton_play_clicked(self):
video_path = "image/myself.mp4" # 已经录制好的视频路径
capture = cv2.VideoCapture(video_path) # 初始化播放器
while True:
flag, frame = capture.read()
if flag is False:
break
self.display_image(frame, self.label) # 显示帧到标签
key = cv2.waitKey(25)
if key == 27:
break
capture.release()
def display_image(self, frame, label):
pic_image = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB) # 将BGR格式图像转换成RGB
height, width = pic_image.shape[:2]
pixMap = QImage(
pic_image.data, width, height, width * 3, QImage.Format_RGB888
) # 将RGB格式图像转换为八位图
pixMap = QPixmap.fromImage(pixMap)
ratio = max(width / self.label.width(), height / self.label.height())
pixMap.setDevicePixelRatio(ratio) # 根据图片比例显示
self.label.setAlignment(Qt.AlignCenter) # 设置居中
self.label.setPixmap(pixMap)
if __name__ == "__main__":
app = QApplication(sys.argv)
ui = videoShow()
ui.show()
sys.exit(app.exec_())
```
这样,点击 "开始录制" 按钮将开始录制视频,并将按钮文本更改为 "停止录制"。再次点击 "停止录制" 按钮将停止录制,并保存视频文件。
self.cap.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc('M','J','P','G'))
这行代码是用来设置视频编码器的,它使用了 OpenCV 中的 `cv2.VideoWriter_fourcc()` 函数来指定视频编码器的四字符代码,这里使用的是 MJPG 编码器。四字符代码是一种用于标识视频编码器的短字符串,每个编码器都有自己的唯一代码。在这里,我们将 MJPG 编码器的四字符代码设置为 `'M','J','P','G'`,它代表了 MJPG 编码器。
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