org.opencv.videoio

Class VideoWriter

java.lang.Object

org.opencv.videoio.VideoWriter

public class VideoWriter
extends Object

Video writer class. The class provides C++ API for writing video files or image sequences.

Field Summary

Fields

Modifier and Type	Field and Description
protected long	nativeObj

Constructor Summary

Constructors

Modifier	Constructor and Description
	VideoWriter() Default constructors The constructors/functions initialize video writers.
protected	VideoWriter(long addr)
	VideoWriter(String filename, int fourcc, double fps, Size frameSize)
	VideoWriter(String filename, int fourcc, double fps, Size frameSize, boolean isColor)
	VideoWriter(String filename, int fourcc, double fps, Size frameSize, MatOfInt params) The params parameter allows to specify extra encoder parameters encoded as pairs (paramId_1, paramValue_1, paramId_2, paramValue_2, ...
	VideoWriter(String filename, int apiPreference, int fourcc, double fps, Size frameSize) The apiPreference parameter allows to specify API backends to use.
	VideoWriter(String filename, int apiPreference, int fourcc, double fps, Size frameSize, boolean isColor) The apiPreference parameter allows to specify API backends to use.
	VideoWriter(String filename, int apiPreference, int fourcc, double fps, Size frameSize, MatOfInt params)

Method Summary

Modifier and Type	Method and Description
static VideoWriter	__fromPtr__(long addr)
protected void	finalize()
static int	fourcc(char c1, char c2, char c3, char c4) Concatenates 4 chars to a fourcc code
double	get(int propId) Returns the specified VideoWriter property
String	getBackendName() Returns used backend API name Note: Stream should be opened.
long	getNativeObjAddr()
boolean	isOpened() Returns true if video writer has been successfully initialized.
boolean	open(String filename, int fourcc, double fps, Size frameSize) Initializes or reinitializes video writer.
boolean	open(String filename, int fourcc, double fps, Size frameSize, boolean isColor) Initializes or reinitializes video writer.
boolean	open(String filename, int fourcc, double fps, Size frameSize, MatOfInt params)
boolean	open(String filename, int apiPreference, int fourcc, double fps, Size frameSize)
boolean	open(String filename, int apiPreference, int fourcc, double fps, Size frameSize, boolean isColor)
boolean	open(String filename, int apiPreference, int fourcc, double fps, Size frameSize, MatOfInt params)
void	release() Closes the video writer.
boolean	set(int propId, double value) Sets a property in the VideoWriter.
void	write(Mat image) Writes the next video frame

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

nativeObj

protected final long nativeObj

Constructor Detail

VideoWriter

protected VideoWriter(long addr)

VideoWriter

public VideoWriter()

Default constructors The constructors/functions initialize video writers.

• On Linux FFMPEG is used to write videos;
• On Windows FFMPEG or MSWF or DSHOW is used;
• On MacOSX AVFoundation is used.

VideoWriter

public VideoWriter(String filename,
                   int fourcc,
                   double fps,
                   Size frameSize,
                   boolean isColor)

Parameters:

filename - Name of the output video file.

fourcc - 4-character code of codec used to compress the frames. For example, VideoWriter::fourcc('P','I','M','1') is a MPEG-1 codec, VideoWriter::fourcc('M','J','P','G') is a motion-jpeg codec etc. List of codes can be obtained at [MSDN](https://docs.microsoft.com/en-us/windows/win32/medfound/video-fourccs) page or with this [page](https://fourcc.org/codecs.php) of the fourcc site for a more complete list). FFMPEG backend with MP4 container natively uses other values as fourcc code: see [ObjectType](http://mp4ra.org/#/codecs), so you may receive a warning message from OpenCV about fourcc code conversion.

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. Tips:

• With some backends fourcc=-1 pops up the codec selection dialog from the system.
• To save image sequence use a proper filename (eg. img_%02d.jpg) and fourcc=0 OR fps=0. Use uncompressed image format (eg. img_%02d.BMP) to save raw frames.
• Most codecs are lossy. If you want lossless video file you need to use a lossless codecs (eg. FFMPEG FFV1, Huffman HFYU, Lagarith LAGS, etc...)
• If FFMPEG is enabled, using codec=0; fps=0; you can create an uncompressed (raw) video file.
• If FFMPEG is used, we allow frames of odd width or height, but in this case we truncate the rightmost column/the bottom row. Probably, this should be handled more elegantly, but some internal functions inside FFMPEG swscale require even width/height.

VideoWriter

public VideoWriter(String filename,
                   int fourcc,
                   double fps,
                   Size frameSize)

Parameters:

filename - Name of the output video file.

fourcc - 4-character code of codec used to compress the frames. For example, VideoWriter::fourcc('P','I','M','1') is a MPEG-1 codec, VideoWriter::fourcc('M','J','P','G') is a motion-jpeg codec etc. List of codes can be obtained at [MSDN](https://docs.microsoft.com/en-us/windows/win32/medfound/video-fourccs) page or with this [page](https://fourcc.org/codecs.php) of the fourcc site for a more complete list). FFMPEG backend with MP4 container natively uses other values as fourcc code: see [ObjectType](http://mp4ra.org/#/codecs), so you may receive a warning message from OpenCV about fourcc code conversion.

fps - Framerate of the created video stream.

frameSize - Size of the video frames. will work with grayscale frames. Tips:

• With some backends fourcc=-1 pops up the codec selection dialog from the system.
• To save image sequence use a proper filename (eg. img_%02d.jpg) and fourcc=0 OR fps=0. Use uncompressed image format (eg. img_%02d.BMP) to save raw frames.
• Most codecs are lossy. If you want lossless video file you need to use a lossless codecs (eg. FFMPEG FFV1, Huffman HFYU, Lagarith LAGS, etc...)
• If FFMPEG is enabled, using codec=0; fps=0; you can create an uncompressed (raw) video file.
• If FFMPEG is used, we allow frames of odd width or height, but in this case we truncate the rightmost column/the bottom row. Probably, this should be handled more elegantly, but some internal functions inside FFMPEG swscale require even width/height.

VideoWriter

public VideoWriter(String filename,
                   int apiPreference,
                   int fourcc,
                   double fps,
                   Size frameSize,
                   boolean isColor)

The apiPreference parameter allows to specify API backends to use. Can be used to enforce a specific reader implementation if multiple are available: e.g. cv::CAP_FFMPEG or cv::CAP_GSTREAMER.

Parameters:

filename - automatically generated

apiPreference - automatically generated

fourcc - automatically generated

fps - automatically generated

frameSize - automatically generated

isColor - automatically generated

VideoWriter

public VideoWriter(String filename,
                   int apiPreference,
                   int fourcc,
                   double fps,
                   Size frameSize)

The apiPreference parameter allows to specify API backends to use. Can be used to enforce a specific reader implementation if multiple are available: e.g. cv::CAP_FFMPEG or cv::CAP_GSTREAMER.

Parameters:

filename - automatically generated

apiPreference - automatically generated

fourcc - automatically generated

fps - automatically generated

frameSize - automatically generated

VideoWriter

public VideoWriter(String filename,
                   int fourcc,
                   double fps,
                   Size frameSize,
                   MatOfInt params)

The params parameter allows to specify extra encoder parameters encoded as pairs (paramId_1, paramValue_1, paramId_2, paramValue_2, ... .) see cv::VideoWriterProperties

Parameters:

filename - automatically generated

fourcc - automatically generated

fps - automatically generated

frameSize - automatically generated

params - automatically generated

VideoWriter

public VideoWriter(String filename,
                   int apiPreference,
                   int fourcc,
                   double fps,
                   Size frameSize,
                   MatOfInt params)

Method Detail

getNativeObjAddr

public long getNativeObjAddr()

__fromPtr__

public static VideoWriter __fromPtr__(long addr)

open

public boolean open(String filename,
                    int fourcc,
                    double fps,
                    Size frameSize,
                    boolean isColor)

Initializes or reinitializes video writer. The method opens video writer. Parameters are the same as in the constructor VideoWriter::VideoWriter.

Parameters:

filename - automatically generated

fourcc - automatically generated

fps - automatically generated

frameSize - automatically generated

isColor - automatically generated

Returns:

true if video writer has been successfully initialized The method first calls VideoWriter::release to close the already opened file.

open

public boolean open(String filename,
                    int fourcc,
                    double fps,
                    Size frameSize)

Initializes or reinitializes video writer. The method opens video writer. Parameters are the same as in the constructor VideoWriter::VideoWriter.

Parameters:

filename - automatically generated

fourcc - automatically generated

fps - automatically generated

frameSize - automatically generated

Returns:

true if video writer has been successfully initialized The method first calls VideoWriter::release to close the already opened file.

open

public boolean open(String filename,
                    int apiPreference,
                    int fourcc,
                    double fps,
                    Size frameSize,
                    boolean isColor)

open

public boolean open(String filename,
                    int apiPreference,
                    int fourcc,
                    double fps,
                    Size frameSize)

open

public boolean open(String filename,
                    int fourcc,
                    double fps,
                    Size frameSize,
                    MatOfInt params)

open

public boolean open(String filename,
                    int apiPreference,
                    int fourcc,
                    double fps,
                    Size frameSize,
                    MatOfInt params)

isOpened

public boolean isOpened()

Returns true if video writer has been successfully initialized.

Returns:

automatically generated

release

public void release()

Closes the video writer. The method is automatically called by subsequent VideoWriter::open and by the VideoWriter destructor.

write

public void write(Mat image)

Writes the next video frame

Parameters:

image - The written frame. In general, color images are expected in BGR format. The function/method writes the specified image to video file. It must have the same size as has been specified when opening the video writer.

set

public boolean set(int propId,
                   double value)

Sets a property in the VideoWriter.

Parameters:

propId - Property identifier from cv::VideoWriterProperties (eg. cv::VIDEOWRITER_PROP_QUALITY) or one of REF: videoio_flags_others

value - Value of the property.

Returns:

true if the property is supported by the backend used by the VideoWriter instance.

get

public double get(int propId)

Returns the specified VideoWriter property

Parameters:

propId - Property identifier from cv::VideoWriterProperties (eg. cv::VIDEOWRITER_PROP_QUALITY) or one of REF: videoio_flags_others

Returns:

Value for the specified property. Value 0 is returned when querying a property that is not supported by the backend used by the VideoWriter instance.

fourcc

public static int fourcc(char c1,
                         char c2,
                         char c3,
                         char c4)

Concatenates 4 chars to a fourcc code

Parameters:

c1 - automatically generated

c2 - automatically generated

c3 - automatically generated

c4 - automatically generated

Returns:

a fourcc code This static method constructs the fourcc code of the codec to be used in the constructor VideoWriter::VideoWriter or VideoWriter::open.

getBackendName

public String getBackendName()

Returns used backend API name Note: Stream should be opened.

Returns:

automatically generated

finalize

protected void finalize()
                 throws Throwable

Overrides:

finalize in class Object

Throws:

Throwable