mpeg file

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James 2011-7-19

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I have two task that are similar that I dont know how to do:

1 - I want to be able to import an mpeg video and save each frame of this movie as individual images into a folder.

2 - Also, I want to be able to create an mpeg video given a number of individual images saved in a folder.

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Walter Roberson 2011-7-19

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If you have a new enough MATLAB version, you could perhaps us the VideoReader class; older versions called it the mmreader. Extract frame by frame and use imwrite(). See http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F for information on automatic filename generation for such purposes.

Given a series of frames read in by imread() (in conjunction with dir() to find the file names), you can use the VideoWriter() class to produce a .avi .

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James 2011-7-20

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在 MATLAB Online 中打开

Sorry I need further help...

For task 1: - I have imported the mpeg video using:

object = mmreader('train.mpg')

and I know how to scroll through each frame using:

for i=1:NumberOfFrames
read(object,i)
end

But how do I save this frame as a jpg?

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James 2011-7-21

It seems when I double()a frame I still have the same numbers, which is not what you are saying?! However, when I use im2double() then I do get numbers between 0 and 1.

Walter Roberson 2011-7-21

Yes, double() keeps the same numeric values, such as uint8(42) becoming the double precision number 42.0. That is fine for some kinds of computations, but if you try to display or imwrite() a double precision array with such values you will have problems, as the expected range for representing graphics in double precision variables is 0 to 1. im2double() converts the data type _and_ rescales the values to be in the range 0 to 1.

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