OpenCV讀寫視頻文件解析（二）
VideoCapture::set
設置視頻捕獲中的屬性。
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.
參數：
propId -屬性標識符。它可以是下列之一：
CV_CAP_PROP_POS_MSEC視頻文件的當前位置（毫秒）。
CV_CAP_PROP_POS_FRAMES下一個要解碼/捕獲的幀的基於0的索引。
CV_CAP_PROP_POS_AVI_RATIO視頻文件的相對位置：0-膠片開始，1-膠片結束。
CV_CAP_PROP_FRAME_WIDTH視頻流中幀的寬度。
CV_CAP_PROP_FRAME_HEIGHT視頻流中幀的高度。
CV_CAP_PROP_FPS幀速率。
CV_CAP_PROP_FOURCC編解碼器的4個字符代碼。
CV_CAP_PROP_FRAME_COUNT視頻文件中的幀數。
CV_CAP_PROP_FORMAT retrieve（）返回的Mat對象格式。
CV_CAP_PROP_MODE後端特定值，指示當前捕獲模式。
CV_CAP_PROP_BRIGHTNESS 圖像亮度（僅適用於機）。
CV_CAP_PROP_CONTRAST圖像的對比度（僅適用於機）。
CV_CAP_PROP_SATURATION圖像飽和度（僅適用於相機）。
CV_CAP_PROP_HUE 圖像的色調（僅適用於相機）。
CV_CAP_PROP_GAIN圖像的增益（僅適用於相機）。
CV_CAP_PROP_EXPOSURE曝光（僅適用於相機）。
CV_CAP_PROP_CONVERT_RGB布爾標誌，指示是否應將圖像轉換爲RGB。
CV_CAP_PROP_WHITE_BALANCE_U設置白平衡的U值（注意：當前僅受DC1394v 2.x後端支持）
CV_CAP_PROP_WHITE_BALANCE_V設置白平衡的V值（注意：當前僅受DC1394V 2.x後端支持）
CV_CAP_PROP_RECTIFICATION立體攝像機的校正標誌（注：目前僅受DC1394 v 2.x後端支持）
CV_CAP_PROP_ISO_SPEED相機的ISO速度（注意：當前僅受DC1394v 2.x後端支持）
CV_CAP_PROP_BUFFERSIZE存儲在內部緩衝存儲器中的幀數量（注意：當前僅受DC1394 v 2.x後端支持）
value–屬性的值。
VideoWriter
class VideoWriter
Video writer class.
VideoWriter::VideoWriter
VideoWriter constructors構造
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]]) →
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).
· 參數：
· file Name–輸出視頻文件的名稱。
· fourcc–用於壓縮幀的編解碼器的4字符代碼。例如，CV_FOURCC（‘P’，‘I’，‘M’，‘1’）是MPEG-1編解碼器，CV_FOURCC（‘M’，‘J’，‘P’，‘G’）是運動jpeg編解碼器等。可通過FOURCC頁面在視頻編解碼器處獲得代碼列表。
· fps–創建的視頻流的幀速率。
· frameSize–視頻幀的大小。
· isColor–如果不爲零，編碼器將期望並編碼彩色幀，否則將使用灰度幀（該標誌當前僅在Windows上受支持）。
· 構造函數/函數初始化視頻寫入程序。在Linux上，FFMPEG用於編寫視頻；在Windows上，FFMPEG或VFW用於編寫視頻；在MacOSX上，QTKit用於編寫視頻。
· ReleaseVideoWriter
· 釋放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（）打開的CvVideoWriter之後，應該調用該函數。
· VideoWriter::open
· 初始化或重新初始化視頻編寫器。
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().
· 該方法打開視頻編寫器。參數與構造函數VideoWriter::VideoWriter（）中的參數相同。
· VideoWriter::isOpened
· 如果已成功初始化視頻編寫器，則返回true。
C++: bool VideoWriter::isOpened()
Python: cv2.VideoWriter.isOpened() → retval
VideoWriter::write 寫入下一個視頻幀
C++: VideoWriter& VideoWriter::operator<<(const Mat& image)
C++: void VideoWriter::write(const Mat& image)
Python: cv2.VideoWriter.write(image) → None
C: int cvWriteFrame(CvVideoWriterwriter, const IplImage image)
Python: cv.WriteFrame(writer, image) → int
Parameters:
· writer – Video writer structure (OpenCV 1.x API)
· image – The written frame
參數：
writer—視頻編寫器結構（OpenCV 1.x API）
image –寫入幀
函數/方法將指定的圖像寫入視頻文件。它的大小必須與打開視頻編寫器時指定的大小相同。