OpenCV讀寫視頻文件解析（二）

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后端特定值，指示當前捕獲模式。

CV_CAP_PROP_BRIGHTNESS 圖像亮度（僅適用於相機）。             

CV_CAP_PROP_CONTRAST圖像的對比度（僅適用於相機）。             

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布爾標志，指示是否應將圖像轉換為RGB。

CV_CAP_PROP_WHITE_BALANCE_U設置白平衡的U值（注意：當前僅受DC1394 v 2.x后端支持）             

CV_CAP_PROP_WHITE_BALANCE_V設置白平衡的V值（注意：當前僅受DC1394 V 2.x后端支持）             

CV_CAP_PROP_RECTIFICATION立體攝像機的校正標志（注：目前僅受DC1394 v 2.x后端支持）             

CV_CAP_PROP_ISO_SPEED相機的ISO速度（注意：當前僅受DC1394 v 2.x后端支持）             

CV_CAP_PROP_BUFFERSIZE存儲在內部緩沖存儲器中的幀數量（注意：當前僅受DC1394 v 2.x后端支持）             

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]]) → <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).
• 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–如果不為零，編碼器將期望並編碼彩色幀，否則將使用灰度幀（該標志當前僅在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之后，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(CvVideoWriter* writer, 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。