read

Read one or more video frames

Syntax

video = read(v)

video = read(v,index)

video = read(___,'native')

Description

video = read(v) reads all video frames from the file associated with v.

video = read(v,index) reads only the frames specified by index.

video = read(___,'native') returns data in the format specified by the VideoFormat property and can include any of the input arguments in the previous syntaxes.

Examples

Read Video Frames Using Frame Index

Create a VideoReader object for the sample video file xylophone_video.mp4.

v = VideoReader("xylophone_video.mp4");

Read only the first video frame.

firstFrame = read(v,1);

Read only the last video frame.

lastFrame = read(v,Inf);

Read frames 5 through 10.

earlyFrames = read(v,[5 10]);

Read from the 50th frame to the end of the video file.

lateFrames = read(v,[50 Inf]);

Display the size and type information of the video frame variables.

whos *Frame*

  Name               Size                     Bytes  Class    Attributes

  earlyFrames      240x320x3x6              1382400  uint8              
  firstFrame       240x320x3                 230400  uint8              
  lastFrame        240x320x3                 230400  uint8              
  lateFrames       240x320x3x92            21196800  uint8              

Clear the VideoReader object.

clear v

Input Arguments

v — Input VideoReader object

VideoReader object

Input VideoReader object. Use the VideoReader function to create a VideoReader object from your video file.

index — Frames to read

[1 Inf] (default) | numeric scalar | two-element array

Frames to read, specified as a numeric scalar or a two-element array.

• To read a single frame, specify a numeric scalar.

• To read a range of frames, specify a two-element array.

The first frame number is 1, and Inf represents the last frame of the file.

Example: 10

Example: Inf

Example: [1 20]

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Output Arguments

video — Video frame data

numeric array | structure array

Video frame data, returned as a numeric or structure array. The size and format of video depends on the VideoFormat property of v. When the VideoFormat property of v is 'Indexed' or 'Grayscale', the data type and dimensions of video depend on whether you call read with the 'native' argument. For most files, the data type and dimensions of video are as follows.

H is the image frame height, W is the image frame width, and F is the number of frames read.

Value of obj.VideoFormat	Data Type of video	Dimensions of video	Description
'RGB24', with or without specifying 'native'	uint8	H-by-W-by-3-by-F	RGB24 image
'Grayscale', without specifying 'native'	uint8	H-by-W-by-1-by-F	Grayscale image
'Indexed', without specifying 'native'	uint8	H-by-W-by-3-by-F	RGB24 image
'Grayscale' or 'Indexed', specifying 'native'	struct	1-by-F	MATLAB® movie, which is an array of frame structure arrays, each containing the fields cdata and colormap.

For Motion JPEG 2000 files, the data type and dimensions of video are as follows.

Value of obj.VideoFormat	Data Type of video	Dimensions of video	Description
'Mono8'	uint8	H-by-W-by-1-by-F	Mono image
'Mono8 Signed'	int8	H-by-W-by-1-by-F	Mono signed image
'Mono16'	uint16	H-by-W-by-1-by-F	Mono image
'Mono16 Signed'	int16	H-by-W-by-1-by-F	Mono signed image
'RGB24'	uint8	H-by-W-by-3-by-F	RGB24 image
'RGB24 Signed'	int8	H-by-W-by-3-by-F	RGB24 signed image
'RGB48'	uint16	H-by-W-by-3-by-F	RGB48 image
'RGB48 Signed'	int16	H-by-W-by-3-by-F	RGB48 signed image

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• Code generation for read does not support the optional positional argument native.

• Generate Code That Uses Row-Major Layout — Generate Code That Uses Row-Major Array Layout (MATLAB Coder).

Version History

Introduced in R2010b