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OpenCV读写视频文件解析（二）

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07/27
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OpenCV读写视频文件解析（二）

VideoCapture::set

设置视频捕获中的属性。

C++:bool VideoCapture::set(int propId, double value)

Python:cv2.VideoCapture.set(propId, value) → retval

C:int cvSetCaptureProperty(CvCapture* capture, int property_id, double value)

Python:cv.SetCaptureProperty(capture, property_id, value) → retval

Parameters:

  • propId –

Property identifier. It can be one of the following:

o   CV_CAP_PROP_POS_MSEC Current position of the video file in milliseconds.

o   CV_CAP_PROP_POS_FRAMES 0-based index of the frame to be decoded/captured next.

o   CV_CAP_PROP_POS_AVI_RATIO Relative position of the video file: 0 - start of the film, 1 - end of the film.

o   CV_CAP_PROP_FRAME_WIDTH Width of the frames in the video stream.

o   CV_CAP_PROP_FRAME_HEIGHT Height of the frames in the video stream.

o   CV_CAP_PROP_FPS Frame rate.

o   CV_CAP_PROP_FOURCC 4-character code of codec.

o   CV_CAP_PROP_FRAME_COUNT Number of frames in the video file.

o   CV_CAP_PROP_FORMAT Format of the Mat objects returned by retrieve() .

o   CV_CAP_PROP_MODE Backend-specific value indicating the current capture mode.

o   CV_CAP_PROP_BRIGHTNESS Brightness of the image (only for cameras).

o   CV_CAP_PROP_CONTRAST Contrast of the image (only for cameras).

o   CV_CAP_PROP_SATURATION Saturation of the image (only for cameras).

o   CV_CAP_PROP_HUE Hue of the image (only for cameras).

o   CV_CAP_PROP_GAIN Gain of the image (only for cameras).

o   CV_CAP_PROP_EXPOSURE Exposure (only for cameras).

o   CV_CAP_PROP_CONVERT_RGB Boolean flags indicating whether images should be converted to RGB.

o   CV_CAP_PROP_WHITE_BALANCE_U The U value of the whitebalance setting (note: only supported by DC1394 v 2.x backend currently)

o   CV_CAP_PROP_WHITE_BALANCE_V The V value of the whitebalance setting (note: only supported by DC1394 v 2.x backend currently)

o   CV_CAP_PROP_RECTIFICATION Rectification flag for stereo cameras (note: only supported by DC1394 v 2.x backend currently)

o   CV_CAP_PROP_ISO_SPEED The ISO speed of the camera (note: only supported by DC1394 v 2.x backend currently)

o   CV_CAP_PROP_BUFFERSIZE Amount of frames stored in internal buffer memory (note: only supported by DC1394 v 2.x backend currently)

  • value – Value of the property.

参数：

propId -属性标识符。它可以是下列之一：

CV_CAP_PROP_POS_MSEC视频文件的当前位置（毫秒）。

CV_CAP_PROP_POS_FRAMES下一个要解码/捕获的帧的基于0的索引。

CV_CAP_PROP_POS_AVI_RATIO视频文件的相对位置：0-胶片开始，1-胶片结束。

CV_CAP_PROP_FRAME_WIDTH视频流中帧的宽度。

CV_CAP_PROP_FRAME_HEIGHT视频流中帧的高度。

CV_CAP_PROP_FPS帧速率。

CV_CAP_PROP_FOURCC编解码器的4个字符代码。

CV_CAP_PROP_FRAME_COUNT视频文件中的帧数。

CV_CAP_PROP_FORMAT retrieve（）返回的Mat对象格式。

CV_CAP_PROP_MODE后端特定值，指示当前捕获模式。

CV_CAP_PROP_BRIGHTNESS 图像亮度（仅适用于相机）。

CV_CAP_PROP_CONTRAST图像的对比度（仅适用于相机）。

CV_CAP_PROP_SATURATION图像饱和度（仅适用于相机）。

CV_CAP_PROP_HUE  图像的色调（仅适用于相机）。

CV_CAP_PROP_GAIN图像的增益（仅适用于相机）。

CV_CAP_PROP_EXPOSURE曝光（仅适用于相机）。

CV_CAP_PROP_CONVERT_RGB布尔标志，指示是否应将图像转换为RGB。

CV_CAP_PROP_WHITE_BALANCE_U设置白平衡的U值（注意：当前仅受DC1394 v 2.x后端支持）

CV_CAP_PROP_WHITE_BALANCE_V设置白平衡的V值（注意：当前仅受DC1394 V 2.x后端支持）

CV_CAP_PROP_RECTIFICATION立体摄像机的校正标志（注：目前仅受DC1394 v 2.x后端支持）

CV_CAP_PROP_ISO_SPEED相机的ISO速度（注意：当前仅受DC1394 v 2.x后端支持）

CV_CAP_PROP_BUFFERSIZE存储在内部缓冲存储器中的帧数量（注意：当前仅受DC1394 v 2.x后端支持）

value–属性的值。

VideoWriter

class VideoWriter

Video writer class.

VideoWriter::VideoWriter

VideoWriter constructors构造

C++:VideoWriter::VideoWriter()

C++:VideoWriter::VideoWriter(const string& filename, int fourcc, double fps, Size frameSize, bool isColor=true)

Python:cv2.VideoWriter([filename, fourcc, fps, frameSize[, isColor]]) → <VideoWriter object>

C:CvVideoWriter* cvCreateVideoWriter(const char* filename, int fourcc, double fps, CvSize frame_size, int is_color=1 )

Python:cv.CreateVideoWriter(filename, fourcc, fps, frame_size, is_color=true) → CvVideoWriter

Python:cv2.VideoWriter.isOpened() → retval

Python:cv2.VideoWriter.open(filename, fourcc, fps, frameSize[, isColor]) → retval

Python:cv2.VideoWriter.write(image) → None

Parameters:

  • filename – Name of the output video file.
  • fourcc – 4-character code of codec used to compress the frames. For example,
  • CV_FOURCC('P','I','M','1') is a MPEG-1 codec,
  • CV_FOURCC('M','J','P','G') is a motion-jpeg codec etc. List of codes can be obtained at Video Codecs by FOURCC page.
  • fps – Framerate of the created video stream.
  • frameSize – Size of the video frames.
  • isColor – If it is not zero, the encoder will expect and encode color frames, otherwise it will work with grayscale frames (the flag is currently supported on Windows only).
  • 参数：
  • file Name–输出视频文件的名称。
  • fourcc–用于压缩帧的编解码器的4字符代码。例如，CV_FOURCC（'P'，'I'，'M'，'1'）是MPEG-1编解码器，CV_FOURCC（'M'，'J'，'P'，'G'）是运动jpeg编解码器等。可通过FOURCC页面在视频编解码器处获得代码列表。
  • fps–创建的视频流的帧速率。
  • frameSize–视频帧的大小。
  • isColor–如果不为零，编码器将期望并编码彩色帧，否则将使用灰度帧（该标志当前仅在Windows上受支持）。
  • 构造函数/函数初始化视频写入程序。在Linux上，FFMPEG用于编写视频；在Windows上，FFMPEG或VFW用于编写视频；在MacOSX上，QTKit用于编写视频。
  • ReleaseVideoWriter
  • 释放AVI writer。
  • C:void cvReleaseVideoWriter(CvVideoWriter** writer)
  • The function should be called after you finished using CvVideoWriter opened with CreateVideoWriter().
  • 在使用完用CreateVideoWriter（）打开的CvVideoWriter之后，应该调用该函数。
  • VideoWriter::open
  • 初始化或重新初始化视频编写器。

C++:bool VideoWriter::open(const string& filename, int fourcc, double fps, Size frameSize, bool isColor=true)

Python:cv2.VideoWriter.open(filename, fourcc, fps, frameSize[, isColor]) → retval

  • The method opens video writer. Parameters are the same as in the constructor
  • VideoWriter::VideoWriter()
  • 该方法打开视频编写器。参数与构造函数VideoWriter::VideoWriter（）中的参数相同。
  • VideoWriter::isOpened
  • 如果已成功初始化视频编写器，则返回true。

C++:bool VideoWriter::isOpened()

Python:cv2.VideoWriter.isOpened() → retval

VideoWriter::write

写入下一个视频帧

C++:VideoWriter& VideoWriter::operator<<(const Mat& image)

C++:void VideoWriter::write(const Mat& image)

Python:cv2.VideoWriter.write(image) → None

C:int cvWriteFrame(CvVideoWriter* writer, const IplImage* image)

Python:cv.WriteFrame(writer, image) → int

Parameters:

  • writer – Video writer structure (OpenCV 1.x API)
  • image – The written frame

参数：

writer—视频编写器结构（OpenCV 1.x API）

image –写入帧

函数/方法将指定的图像写入视频文件。它的大小必须与打开视频编写器时指定的大小相同。