can't play video file

I can't get the final video to play. It has a size of 1x1 when it should be 401x401.

I'm using R2014a

dir = '/Users/douglasbrenner/Documents/Rosen/AOSLO_MA_AVIs/';

base_name = 'media';

nimages = 11;

size = 31; %size of subimage around alignment point must be odd. 

size_from_center = (size - 1)/2;

for i = 3:3%nimages
    avi = [dir,base_name,int2str(i),'.avi'];
    disp('Converting')
    disp(avi)
    a = VideoReader(avi)

      v = VideoWriter('aligned.avi','Uncompressed AVI');
      open(v);
      n_frames = a.NumberOfFrames
      figure(1);
      frame = read(a,1);
      imshow(frame);
      [Xc(1),Yc(1)] = getpts(1);
      subframe = frame(int16(Yc(1)) - size_from_center:int16(Yc(1))+size_from_center,int16(Xc(1))-size_from_center:int16(Xc(1))+size_from_center);
      center = centroid(subframe,size);
      yc1 = Yc(1);
      xc1 = Xc(1);
      Xc(1) = center(2) - size_from_center;
      Yc(1) = center(1) - size_from_center;
      J = imtranslate(frame,[Xc(1),Yc(1)],'cubic');
      writeVideo(v,uint8(J(a.Height)))

      for j = 2:5%n_frames
          j
          frame = read(a,j);
          subframe = frame(int16(yc1) - size_from_center:int16(yc1)+size_from_center,int16(xc1)-size_from_center:int16(xc1)+size_from_center);
          center = centroid(subframe,size);
          Xc(j) = center(2) - size_from_center;
          Yc(j) = center(1) - size_from_center;
          J = imtranslate(frame,[Xc(j),Yc(j)],'cubic');
          writeVideo(v,uint8(J(a.Height)))

      end
  %  
      Mx = mean(Xc)
      Sx = std(Xc)
      My = mean(Yc)
      Sy = std(Yc)        
  end
  close(v);
  avi = 'aligned.avi';
  a = VideoReader(avi);
  implay(a);

thanks

Answer 1

[Douglas]

This code works. I now I need to learn how to have two movie players open at once and adjust the frame rates.

dir = '/Users/douglasbrenner/Documents/Rosen/AOSLO_MA_AVIs/';
base_name = 'media';
nimages = 11;
size = 31; %size of subimage around alignment point must be odd. 
size_from_center = (size - 1)/2;

for i = 3:3%nimages
    avi = [dir,base_name,int2str(i),'.avi'];
    disp('Converting')
    disp(avi)
    a = VideoReader(avi)
    implay(avi)
    v = VideoWriter('aligned.avi','Uncompressed AVI');
    open(v);
    n_frames = a.NumberOfFrames
    figure(1);
    frame = read(a,1);
    imshow(frame);
    [Xc(1),Yc(1)] = getpts(1);
    subframe = frame(int16(Yc(1)) - size_from_center:int16(Yc(1))+size_from_center,int16(Xc(1))-size_from_center:int16(Xc(1))+size_from_center);
    center = centroid(subframe,size);
    yc1 = Yc(1);
    xc1 = Xc(1);
    Xc(1) = center(2) - size_from_center;
    Yc(1) = center(1) - size_from_center;
    J = imtranslate(frame,[Xc(1),Yc(1)],'cubic');
    writeVideo(v,uint8(J(1:a.Height,1:a.Width)))

      for j = 2:n_frames
          j
          frame = read(a,j);
          subframe = frame(int16(yc1) - size_from_center:int16(yc1)+size_from_center,int16(xc1)-size_from_center:int16(xc1)+size_from_center);
          center = centroid(subframe,size);
          Xc(j) = center(2) - size_from_center;
          Yc(j) = center(1) - size_from_center;
          J = imtranslate(frame,[Xc(j),Yc(j)],'cubic');
          writeVideo(v,uint8(J(1:a.Height,1:a.Width)))

      end
  %  
      Mx = mean(Xc)
      Sx = std(Xc)
      My = mean(Yc)
      Sy = std(Yc)
      close(v);
  end

avi = 'aligned.avi'
implay(avi);

Answer 2

[Walter Roberson]

You create your VideoWriter within the for i loop but you do not close it until after the for i loop. That would mess up your output.

[Walter Roberson]

In your line

        writeVideo(v,uint8(J(a.Height)))

a.Height is going to be a single scalar, so you are accessing your frame data at a single location, converting the resulting scalar to a uint8 and writing out that scalar.

[Douglas]

In the workspace it still says that v is a 1x1 VideoWriter. Doesn't that suggest what to do?

Answer 3

[Douglas]

You are right about the open statement being in the loop with the close outside but the loop only executes once. Nevertheless, I moved the close into the loop where it belongs and changed the video write to writeVideo(v,uint8(J(a.Height,a.Width))). I get a Movie Player Window with a message that says Invalid video data which is what I had before.

[Walter Roberson]

a.Height and a.Width are scalars. J(a.Height, a.Width) is going to give you a scalar output.

Possibly you want

writeVideo(v,uint8( J(1:a.Height, 1:a.Width)))

A question: is your input RGB or is it indexed or is it grayscale ? Your code treats it as grayscale.

[Douglas]

I thought you had it but I got this error: Error using VideoWriter/writeVideo (line 383) Frame must be 1 by 1

Error in avi_to_single_frames (line 37) writeVideo(v,uint8(J(1:a.Height,1:a.Width)))

It would seem the size has to be established when v is created. Yes it's grayscale.

[Walter Roberson]

Did you change both writeVideo calls? You could get that error if you missed changing the first one.

Answer 4

[Douglas]

I tried changing the first writeVideo but couldn't figure out how.