MATLAB视频处理

MATLAB AVI视频资源处理方案

1、用matlab读取avi电影（只能读一定压缩各式的avi电影）

aviinfo('d:\j.avi');%显示存在d盘的电影j.avi的信息,在matlab2010版本中，该函数换成mmreader

mov=aviread('d:\j.avi');%读入存在d盘的电影j.avi

movie(mov);%放映电影

2、将电影转成图片序列

mov=aviread('d:\j.avi');%读入

fnum=size(mov,2); %读取电影的祯数，mov为1*temp

for i=1:fnum

strtemp=strcat('d:\转换的图片\',int2str(i),'.','jpg'); %将每祯转成jpg的图片

imwrite(mov(i).cdata(:,:,Smile,mov(i).colormap,strtemp);

end

3、aviread有两种使用方式：

aviread(filename);

aviread(filename, index);%读取avi文件的第index帧图像；

例：

mov = aviread('highwayI_raw.A VI')

mov = aviread('highwayI_raw.A VI',1) %读取第一帧图像

4、读取图像以后储存的格式是一个结构体，该结构体有两个元素：cdata和colormap

例：

frame = aviread('highwayI_raw.A VI', i);

frame.cdata 表示了一个数据数组，彩色图像就是3维的，灰度图像就是2维的。

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frame.colormap 见（help aviread)

5、将彩色图像转换为灰度图像，很简单：

frame = aviread('highwayI_raw.A VI', i);

f_gray = rgb2gray(frame.cdata); 这样就可以将文件的第i帧转换为灰度图像。

6、 imwrite的用法：

imwrite(recover_image, 'recover.jpg', 'jpg');

在matlab2010中，上述的函数都发生了变化：

读取函数为mmreader,该函数可以读取所有的多媒体文件，返回值为一个结构体；然后可以用read函数进行读取文件，用法如下例：readobj = mmreader('Laboratory_raw.avi');

vidframe = read(readobj);

mov.cdata = vidframe(:,:,:,1);

mov.colormap = [];

movie(mov);

7、doc aviread from MATLAB

aviread

Read Audio/Video Interleaved (AVI) file

Note aviread will be removed in a future release. Use VideoReader instead.

Syntax

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mov = aviread(filename)

mov = aviread(filename, index)

Description

mov = aviread(filename) reads the AVI movie filename into the MATLAB movie structure mov. If filename does not include an extension, then .avi is used. Use the movie function to view the movie mov. On UNIX platforms, filename must be an uncompressed AVI file.

mov has two fields, cdata and colormap. The content of these fields varies depending on the type of image.

Image Type cdata Field colormap Field

Truecolor Height-by-width-by-3 array of uint8 values Empty

Indexed Height-by-width array of uint8 values m-by-3 array of double values

aviread supports 8-bit frames, for indexed and grayscale images, 16-bit grayscale images, or 24-bit truecolor images.

Note, however, that movie only accepts 8-bit image frames; it does not accept 16-bit grayscale image frames.

mov = aviread(filename, index) reads only the frames specified by index. index can be a single index or an array of indices into the video stream. In AVI files, the first frame has the index value 1, the second frame has the index value 2, and so on.

8、doc aviinfo from MATLAB

avifile

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Create new Audio/Video Interleaved (AVI) file Syntax

aviobj = avifile(filename )

avifile(filename , ParameterName , ParameterValue )

Description

aviobj = avifile(filename ) creates an avifile object, giving it the name specified in filename , using default values for all avifile object properties. If filename does not include an extension, avifile appends .avi to the

file name. AVI is a file format for storing audio and video data.

avifile returns a handle to an AVI file object aviobj . Use this object to refer to the AVI file in other functions. An AVI file object supports properties and methods that control aspects of the AVI file created.

aviobj = avifile(filename , ParameterName , ParameterValue ) accepts one or more comma-separated parameter

name/value pairs. Set parameter values before any calls to addframe . The following table lists the available parameters and values. Parameter Name

Value

Default

'colormap' An m -by-3 matrix defining the colormap for indexed AVI movies, where m is no more than 256

(236 for Indeo compression).

Valid only when the 'compression' is 'MSVC', 'RLE', or 'None'.

No default

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Parameter Name

Value

Default

'compression'

A text string specifying the compression codec to use. To create an uncompressed file,

specify a value of 'None'.

On UNIX operating systems, the only valid value is 'None'.

On Windows systems, valid values include:

?

'MSVC' ? 'RLE'

? 'Cinepak' on 32-bit systems.

? 'Indeo3' or 'Indeo5' on 32-bit Windows XP systems.

Alternatively, specify a custom compression codec on Windows systems using the four-character code that identifies the codec (typically included in the codec documentation). If MATLAB cannot find the specified codec, it returns an error.

'Indeo5' on Windows systems. 'None' on UNIX systems.

'fps'

A scalar value specifying the speed of the AVI movie in frames per second (fps).

15 fps 'keyframe' For compressors that support temporal compression, the number of key frames per second.

2.1429 key frames per second

'quality' A 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.

Valid only for compressed movies.

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Parameter Name Value

Default

'videoname' A descriptive name for the video stream, no more than 64 characters.

filename

Tips

? On some Windows systems, including all 64-bit systems, the default Indeo ? 5 codec is not available. MATLAB issues a warning, and creates an uncompressed file.

?

On 32-bit Windows XP systems, MATLAB can create AVI files compressed with Indeo 3 and Indeo 5 codecs. However, Microsoft Windows XP Service Pack 3 (SP3) with Security Update 954157 disables playback of Indeo 3 and Indeo 5 codecs in Windows Media ? Player and Internet Explorer ?. Consider specifying a compression value of 'None'. ? avifile cannot write files larger than 2 GB.

? You can use dot notation to set avifile object properties. For example, set the quality property to 100: ?

aviobj = avifile('myavifile'); aviobj.quality = 100;

All property names of an avifile object are the same as the parameter names, except for the keyframe parameter, which corresponds to the KeyFramePerSec property. For example, change keyframe to 2.5: aviobj.KeyFramePerSec = 2.5;

Example

Create the AVI file example.avi:

aviobj = avifile('example.avi','compression','None');

t = linspace(0,2.5*pi,40);

fact = 10*sin(t);

fig=figure;

[x,y,z] = peaks;

for k=1:length(fact)

h = surf(x,y,fact(k)*z);

axis([-3 3 -3 3 -80 80])

axis off

caxis([-90 90])

F = getframe(fig);

aviobj = addframe(aviobj,F);

end

close(fig);

aviobj = close(aviobj);

Alternatives

Use VideoWriter rather than avifile to create AVI files. VideoWriter supports files larger than 2 GB, and by default, creates files with Motion JPEG compression, which all platforms support.

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