Use the VideoWriter function with the open, writeVideo, and close methods to create video files from figures, still images, or MATLAB movies. VideoWriter can create AVI and Motion JPEG 2000 files on all platforms, and MPEG-4 files on Windows 7 platforms. VideoWriter supports files larger than 2 GB, which is the limit for avifile.

To set video properties, VideoWriter includes predefined profiles such as 'Uncompressed AVI' or 'MPEG-4'.

Construction

writerObj = VideoWriter(filename) constructs a VideoWriter object to write video data to a compressed AVI file.

writerObj = VideoWriter(filename,profile) applies a set of properties tailored to a specific file format (such as 'MPEG-4' or 'Uncompressed AVI') to a VideoWriter object.

Input Arguments

filename

String enclosed in single quotation marks that specifies the name of the file to create.

VideoWriter supports these file extensions:

`.avi`	AVI file
`.mj2`	Motion JPEG 2000 file
`.mp4` or `.m4v`	MPEG-4 file (Windows 7 systems only)

If you do not specify the file extension, VideoWriter appends the extension .avi, .mj2 or .mp4, depending on the profile. If you do not specify a value for profile, then VideoWriter creates an AVI file with the extension .avi.

profile

String enclosed in single quotation marks that describes the type of file to create. Specifying a profile sets default values for video properties such as VideoCompressionMethod. Possible values:

`'Archival'`	Motion JPEG 2000 file with lossless compression
`'Motion JPEG AVI'`	Compressed AVI file using Motion JPEG codec
`'Motion JPEG 2000'`	Compressed Motion JPEG 2000 file
`'MPEG-4'`	Compressed MPEG-4 file with H.264 encoding (Windows 7 systems only)
`'Uncompressed AVI'`	Uncompressed AVI file with `RGB24` video

Default: 'Motion JPEG AVI'

Properties

ColorChannels

Number of color channels in each output video frame. (Read-only)

AVI and MPEG-4 files have three color channels (RGB). The number of channels for Motion JPEG 2000 files depends on the input data to the writeVideo method: one for monochrome image data, three for color data.

CompressionRatio

Number greater than 1 that specifies the target ratio between the number of bytes in the input image and the number of bytes in the compressed image. The data is compressed as much as possible, up to the specified target.

Only available for objects associated with Motion JPEG 2000 files. After you call open, you cannot change the CompressionRatio value. If you previously set LosslessCompression to true, setting CompressionRatio generates an error.

Default: 10

Duration

Scalar value specifying the duration of the file in seconds. (Read-only)

FileFormat

String specifying the type of file to write: 'avi', 'mp4', or 'mj2'. (Read-only)

Filename

String specifying the name of the file. (Read-only)

FrameCount

Number of frames written to the video file. (Read-only)

FrameRate

Rate of playback for the video in frames per second. After you call open, you cannot change the FrameRate value.

Default: 30

Height

Height of each video frame in pixels. The writeVideo method sets values for Height and Width based on the dimensions of the first frame. (Read-only)

MPEG-4 files require frame dimensions that are divisible by two. If the input frame height for an MPEG-4 file is not an even number, VideoWriter pads the frame with a row of black pixels at the bottom.

LosslessCompression

Boolean value (logical true or false) only available for objects associated with Motion JPEG 2000 files. If true:

The writeVideo method uses reversible mode so that the decompressed data is identical to the input data.
VideoWriter ignores any specified value for CompressionRatio.

After you call open, you cannot change the LosslessCompression value.

Default: false for the 'Motion JPEG 2000' profile, true for the 'Archival' profile

MJ2BitDepth

Number of least significant bits in the input image data, from 1 to 16.

Only available for objects associated with Motion JPEG 2000 files. If you do not specify a value before calling the open method, VideoWriter sets the bit depth based on the input data type. For example, if the input data to writeVideo is an array of uint8 or int8 values, MJ2BitDepth is 8.

Path

String specifying the fully qualified path. (Read-only)

Quality

Number from 0 through 100. Higher quality numbers result in higher video quality and larger file sizes. Lower quality numbers result in lower video quality and smaller file sizes.

Only available for objects associated with the MPEG-4 or Motion JPEG AVI profile. After you call open, you cannot change the Quality value.

Default: 75

VideoBitsPerPixel

Number of bits per pixel in each output video frame. (Read-only)

AVI and MPEG-4 files have 24 bits per pixel (8 bits for each of three color bands).

For Motion JPEG 2000 files, the number of bits per pixel depends on the value of MJ2BitDepth and the number of bands of image data. For example, if the input data to writeVideo is a three-dimensional array of uint16 or int16 values, the default value of MJ2BitDepth is 16, and VideoBitsPerPixel is 48 (three times the bit depth).

VideoCompressionMethod

String indicating the type of video compression: 'None', 'H.264', 'Motion JPEG', or 'Motion JPEG 2000'. (Read-only)

VideoFormat

String indicating the MATLAB representation of the video format. (Read-only)

For AVI or MPEG-4 files, VideoFormat is 'RGB24'.

For Motion JPEG 2000 files, VideoFormat depends on the value of MJ2BitDepth and the format of the input image data to the writeVideo method. For example, if you do not specify the MJ2BitDepth property, VideoWriter sets the format as shown in this table.

Image Data VideoFormat

Single-band uint8 'Mono8'

Single-band int8 'Mono8 Signed'

Single-band uint16 'Mono16'

Single-band int16 'Mono16 Signed'

Three-banded uint8 'RGB24'

Three-banded int8 'RGB24 Signed'

Three-banded uint16 'RGB48'

Three-banded int16 'RGB48 Signed'

Width

Width of each video frame in pixels. The writeVideo method sets values for Height and Width based on the dimensions of the first frame. (Read-only)

MPEG-4 files require frame dimensions that are divisible by two. If the input frame width for an MPEG-4 file is not an even number, VideoWriter pads the frame with a column of black pixels along the right side.

Methods

close	Close file after writing video data
getProfiles	List profiles and file formats supported by `VideoWriter`
open	Open file for writing video data
writeVideo	Write video data to file

Copy Semantics

Handle. To learn how handle classes affect copy operations, see Copying Objects in the MATLAB Programming Fundamentals documentation.

Examples

Object Properties

Construct a VideoWriter object and view its properties.

writerObj = VideoWriter('newfile.avi')

Set the frame rate to 60 frames per second.

writerObj.FrameRate = 60;

AVI File from Animation

Write a sequence of frames to a compressed AVI file, peaks.avi.

Prepare the new file.

writerObj = VideoWriter('peaks.avi');
open(writerObj);

Generate initial data and set axes and figure properties.

Z = peaks; surf(Z); 
axis tight
set(gca,'nextplot','replacechildren');
set(gcf,'Renderer','zbuffer');

Setting the Renderer property to zbuffer or Painters works around limitations of getframe with the OpenGL renderer on some Windows systems.

Create a set of frames and write each frame to the file.

for k = 1:20 
   surf(sin(2*pi*k/20)*Z,Z)
   frame = getframe;
   writeVideo(writerObj,frame);
end

close(writerObj);

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VideoWriter class -

Description