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randomly picking a fram from a video in matlab

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KT
KT 2012-4-25
my problem is that i want to randomly pick a frame from a video , using mmreader , and also i am getting the last frame of the video so that i can set limit, so that when using rand function the number can be picked from 1 to the last frame number,the code is;
readerobj = mmreader(myvideoname);
last_Frame_number = read(readerobj, inf);
end_frame=readerobj.NumberOfFrames;
random_frame=randi([1,end_frame]);
can someone tell a better solution because this take alot of time because every video has a varying size , and i want to make it more efficient.
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KT
KT 2012-4-25
and longer the video size more time it takes as it needs to fetch the last frame number

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Walter Roberson
Walter Roberson 2012-4-25
For videos that are not variable-frame-rate, the NumberOfFrames property will be set when the object is created. If you are not getting a warning when you create the object (before you even do anything to it) then the NumberOfFrames will reflect the total number in the file.
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Walter Roberson
Walter Roberson 2012-4-26
Show your current code, and indicate which line it runs out of memory on.
KT
KT 2012-4-26
readerobj = mmreader('myvideo.mpg');
last_Frame = read(readerobj, inf);
last_Frame_number=readerobj.NumberOfFrames;
frame_rand=randi([1,last_Frame_number]);
vidFrames = read(readerobj,frame_rand);
this is my code, it takes alot of time, and if i run on loop like for 5 times, it gives timeout error.

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