video - Matlab thinks an AVI it's written is corrupt -

i'm using matlab interface scientific camera using mex, , matlab program uses videowriter() write file disc. camera rgb-capable, , if write file such, video fine. however, current application, need grayscale images, , i'm using rgb2gray() convert it. unfortunately, when analysis code tried read video file again, error:

error using videoreader/init (line 450) unable read file. file appears corrupt. 

and attempting read video vlc confirms corrupt. difference in code between grayscale , colour versions line:

frame = rgb2gray(frame); 

my whole writing section of code is:

vid = videowriter('testvid.avi'); vid.framerate = framerate; vid.quality = 100; open(vid); = 1 : frames;     %read frame data variable 'frame'     frame = rgb2gray(frame);     writevideo(vid,frame); end 

i've spent far long fighting this, ideas?

you need close video object, using close(vid) after writing last frame.