Setting frames from mid video

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Daevin
Daevin on 19 Aug 2014
Edited: Geoff Hayes on 21 Aug 2014
I need to take 300 frames from the middle of a huge video (20000 frames) to do further manipulation. I got the following from the xylophone example but it only takes frames from the start of the video; I need to set a smaller video from frames 3701:4000:
Clip1 = VideoReader('C:\Users\(username)\Videos\Day3.4.avi'); %xylophone.mp4');
nFrames = 500; %Clip1.NumberOfFrames;
vidHeight = Clip1.Height;
vidWidth = Clip1.Width;
%%Movie Structure
mov(1:nFrames) = ...
struct('cdata',zeros(vidHeight,vidWidth, 3,'uint8'),...
'colormap',[]);
%%Reading frames
for k = 1 : nFrames
mov(k).cdata = read(Clip1,k);
end
hf = figure;
set(hf, 'position', [150 150 vidWidth vidHeight])
Any help would be greatly appriciated.

Accepted Answer

Geoff Hayes
Geoff Hayes on 20 Aug 2014
Edited: Geoff Hayes on 21 Aug 2014
Daevin - according to videoreader.read, it is possible to read in whichever frame that you wish
video = read(obj,index) reads only the specified frames. index can be a single number or a two-element array representing an index range of the video stream.
If you are interested only in the 300 frames starting at 3701, then your above code could be modified as
nFrames = 300; %Clip1.NumberOfFrames;
vidHeight = Clip1.Height;
vidWidth = Clip1.Width;
%%Movie Structure
mov(1:nFrames) = ...
struct('cdata',zeros(vidHeight,vidWidth, 3,'uint8'),'colormap',[]);
%%Reading frames
for k = 1:nFrames
mov(k).cdata = read(Clip1,3700+k);
end
Try the above and see what happens!
EDIT
Corrected the numFrames to nFrames as per Daevin's comment below.
  1 Comment
Daevin
Daevin on 21 Aug 2014
Fantastic. Of course its the last placement I didn't try. For anyone that uses this, change the numFrames to nFrames.

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