如何使用 Matlab 从给定的 yuv 文件中提取 Y、U 和 V 分量？每个组件都用于进一步的像素级操作

Question

嘿伙计们。我目前正在使用 YUV 文件。您对如何从 yuv 视频中提取 y,u,v 分量有什么建议吗？我找到程序片段如下所示。但我不知道哪一部分是我想要的有效组件。谢谢。

% function mov = loadFileYuv(fileName, width, height, idxFrame)

function [mov,imgRgb] = loadFileYuv(fileName, width, height, idxFrame)
% load RGB movie [0, 255] from YUV 4:2:0 file

fileId = fopen(fileName, 'r');

subSampleMat = [1, 1; 1, 1];
nrFrame = length(idxFrame);


for f = 1 : 1 : nrFrame

    % search fileId position
    sizeFrame = 1.5 * width * height;
    fseek(fileId, (idxFrame(f) - 1) * sizeFrame, 'bof');

    % read Y component
    buf = fread(fileId, width * height, 'uchar');
    imgYuv(:, :, 1) = reshape(buf, width, height).'; % reshape RESHAPE(X,M,N) returns the M-by-N matrix 
                                                     %whose elements are taken columnwise from X.  
                                                     %An error results if X does not have M*N elements

    % read U component
    buf = fread(fileId, width / 2 * height / 2, 'uchar');
    imgYuv(:, :, 2) = kron(reshape(buf, width / 2, height / 2).', subSampleMat); % reshape and upsample

    % read V component
    buf = fread(fileId, width / 2 * height / 2, 'uchar');
    imgYuv(:, :, 3) = kron(reshape(buf, width / 2, height / 2).', subSampleMat); % reshape and upsample

    % normalize YUV values
    % imgYuv = imgYuv / 255;

    % convert YUV to RGB
    imgRgb = reshape(convertYuvToRgb(reshape(imgYuv, height * width, 3)), height, width, 3);
    % imgRgb = ycbcr2rgb(imgYuv);
    %imwrite(imgRgb,'ActualBackground.bmp','bmp');
    mov(f) = im2frame(imgRgb);
    %   mov(f).cdata = uint8(imgRgb);
    %   mov(f).colormap =  [];
    %     imwrite(imgRgb,'ActualBackground.bmp','bmp');

    %figure, imshow(imgRgb);
    %name = 'ActualBackground.bmp';
    %Image = imread(name, 'bmp');
    %figure, imshow(Image);
end
fclose(fileId);

Answer 1

不确定我是否对 YUV 文件有一些根本性的误解，但如果您像下面那样编辑函数，您就会在名为 imgYUV 的单个变量中获得每个帧的 YUV 分量。请注意，您可能会在此过程中耗尽内存，您可能不想一次性加载电影的所有帧。

function imgYUV = loadFileYuv(fileName, width, height, idxFrame)
% load YUV data from YUV 4:2:0 file

fileId = fopen(fileName, 'r');

subSampleMat = [1, 1; 1, 1];
nrFrame = length(idxFrame);

%# preassign imgYUV. In case we can't keep everything in RAM,
%# it is better that the function crashes here, rather than after
%# having wasted time slowly filling up the memory.
%# Since the images are likely to be of class 'uint8', 
%# you can save on a lot of memory by initializing
%# imgYUV as zeros(width/2,height/2,3,nrFrame,'uint8');
imgYUV = zeros(width/2 height/2, 3, nrFrame);

for f = 1 : 1 : nrFrame

    %# search fileId position
    sizeFrame = 1.5 * width * height;
    fseek(fileId, (idxFrame(f) - 1) * sizeFrame, 'bof');

    %# read Y component
    buf = fread(fileId, width * height, 'uchar');
    imgYuv(:, :, 1, f) = reshape(buf, width, height).'; 

    %# read U component
    buf = fread(fileId, width / 2 * height / 2, 'uchar');
    imgYuv(:, :, 2, f) = kron(reshape(buf, width / 2, height / 2).', subSampleMat); % reshape and upsample

    % read V component
    buf = fread(fileId, width / 2 * height / 2, 'uchar');
    imgYuv(:, :, 3, f) = kron(reshape(buf, width / 2, height / 2).', subSampleMat); % reshape and upsample

end
fclose(fileId);

Answer 2

我只需更改函数定义：

function [mov,imgYuv] = loadFileYuv(fileName, width, height, idxFrame)

无需返回 imgRgb，因为它与 mov(numel(idxFrame)).cdata 相同。

指定两个输出变量，您将在第二个变量中获得最后一帧的 YUV 分量。

---

我会更改该函数来检查缓冲区是否为空，以避免在您要求的帧数多于文件包含的帧数时出现错误。

    ...
    status = fseek(fileId, (idxFrame(f) - 1) * sizeFrame, 'bof');
    if status == -1
        error('Cannot read frame %d',idxFrame(f));
    end

    % read Y component
    buf = fread(fileId, width * height, 'uchar');
    if isempty(buf)
        error('Cannot read frame %d',idxFrame(f));
    end
    imgYuv(:, :, 1) = reshape(buf, width, height).'; % reshape

    % read U component
    buf = fread(fileId, width / 2 * height / 2, 'uchar');
    if isempty(buf)
        error('Cannot read frame %d',idxFrame(f));
    end
    imgYuv(:, :, 2) = kron(reshape(buf, width / 2, height / 2).', subSampleMat); % reshape and upsample

    % read V component
    buf = fread(fileId, width / 2 * height / 2, 'uchar');
    if isempty(buf)
        error('Cannot read frame %d',idxFrame(f));
    end
    ...