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function I = read422(fname,nc);
%
% I = read422(fname,width);
%
% read in a .422 file, need to pass image width, default = 640
%
% assume image width = 640
if nargin<2,
nc = 640;
end
%% find the image size
fid = fopen(fname);
fseek(fid,0,1);
fsize = ftell(fid);
nr = fsize/nc/2;
fseek(fid,0,-1);
%% read in Ybr data
data = fread(fid,fsize,'uchar');
%%% extract Y, Cb, Cr
Y1 = data(1:2:end); Y1 = reshape(Y1,nc,nr)';
Cb1 = data(2:4:end); Cb1 = reshape(Cb1,nc/2,nr)';
Cr1 = data(4:4:end); Cr1 = reshape(Cr1,nc/2,nr)';
Cb = zeros(size(Y1));
Cr = zeros(size(Y1));
Cb(:,1:2:end) = Cb1; Cb(:,2:2:end) = Cb1;
%Cb(:,2:2:end) = 0.5*(Cb1+[Cb1(:,2:end),Cb1(:,end)]);
Cr(:,1:2:end) = Cr1; Cr(:,2:2:end) = Cr1;
%Cr(:,2:2:end) = 0.5*(Cr1+[Cr1(:,2:end),Cr1(:,end)]);
%%% convert to r,g,b
r = 1.164*(Y1-16.0) + 1.596*(Cr-128.0);
g = 1.164*(Y1-16.0) - 0.813*(Cr-128.0) - 0.391*(Cb-128.0);
b = 1.164*(Y1-16.0) + 2.018*(Cb-128.0);
r = flipud(max(0,min(r,255)));
g = flipud(max(0,min(g,255)));
b = flipud(max(0,min(b,255)));
I = cat(3,r,g,b);
I = permute(I/255,[2,1,3]);
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