This code is great. It can be sped up dramatically though by rewriting the clipValue function in a vectorized fashion. That is, replace the code in clipValue.m with these two lines:
val(val < valMin) = valMin;
val(val > valMax) = valMax;
for me this sped up conversion from >8s to <0.3s for a 2560 pixels x 1280 pixels image.
I Am try to execute function [mov,imgRgb] = loadFileYuv(fileName, width, height, idxFrame) but matlab send to me this message :-
??? function [mov,imgRgb] = loadFileYuv(fileName, width, height, idxFrame)
|
Error: Function definitions are not permitted in this context.
I am little confused how he's separating Y,U and V components here,because I am not sure how data is saved in a YUV file. when he first uses uses buf = fread(fileId, width * height, 'uchar'); and after reshaping this data he uses fread(fileId,width/2*height/2,'uchar')
that is 1/4 of the data used in previous 'fread' function and because there is no fseek between these 2 fread function and the next fread function the read data should be the same(atleast first 1/4 part of the data read using fread(fileId,height*width,'uchar') and fread(fileID,height/2*width/2,'uchar')).I am also not getting why/how he's using 'kron' to reshape the U and V components.
Shashi, I believe you are referring to the line
sizeFrame = 1.5 * width * height;
occuring in the file loadFileYuv.m.
The author is preparing enough memory to be able to load one whole YUV (or YCbCr) 4:2:0 frame. This type of video encoding is called "Chroma Subsampling". 4:2:0 means that all luminance values of the scene are recorded, but Cb and Cr are each subsampled at a factor of 2 both horizontally and vertically. This means the total amount of data required to store each frame is:
Total = luminance + Cb + Cr
Total = full resolution + 1/4 res + 1/4 res
Total = 1.5 * full resolution
For more information, see Wikipedia's article on Chroma Subsampling:
http://en.wikipedia.org/wiki/Chroma_subsampling
Chroma subsampling is also discussed at 24:21 minutes through A Digital Media Primer for Geeks at:
http://xiph.org/video/
I have matlab 7.0.1 and unfortunately i can't find functions for yuv, e.g i want to load yuv file into matlab and i cannot find the appropriate function, help? thank you
"idxFrame" is the frame number within the YUV 4:2:0 video you want extracted to an RGB image. Thus, each time you run the function loadFileYuv, it will open the YUV file, extract the specified frame from the video file in the fileName string, and close the YUV file.
For sample YUV 4:2:0 files, use the Video Trace Library at http://trace.eas.asu.edu/yuv/index.html
A versatile and extremely reliable YUV player is located here: http://www.yuvplayer.com/index.html
It is now freeware, as evidenced by here: http://www.yuvplayer.com/register.html
Currently the program lacks an example of how to use the code.
e.g. in the file, loadFileYuv.m, the function call is:
function [mov,imgRgb] = loadFileYuv(fileName, width, height, idxFrame)
What is idxFrame? I thought it might be frames per second, but the code seems to indicate it is some sort of structure. Does this mean the YUV video file needs to be loaded into MATLAB as a variable before this subroutine is used?
It seems like this code may work well, but it just needs an example so most people can use it!! Any help would be appreciated.
hi
i need to convert yuv sequences downloaded from http://www.cipr.rpi.edu/resource/sequences/
into 4:2:0 yuv video file.
if you have any idea. please help me out.
I need to convert a YUV file into a YUV16 file and also a RAW file. Then I need to convert back from these two variants to YUV.
Could this be altered to accomodate this?
25 Feb 2008
Jeo Jaje
It seems a good code. But I need reverse of this. I want to write a 4:2:0 YUV file from a sequence of 2D image files (matrix form). Any idea? please help.
