H.264帧内预测编码matlab

H.264是一种视频编码标准，其中的帧内预测是其中一种压缩技术。在MATLAB中实现H.264编码可以使用一些开源库和工具，例如JM、x264等。以下是一个示例代码，实现了H.264帧内预测编码：

% Read input video
vidObj = VideoReader('input_video.mp4');

% Create output video object
outputVideo = VideoWriter('output_video.mp4','MPEG-4');
outputVideo.FrameRate = vidObj.FrameRate;
open(outputVideo);

% Set H.264 encoder parameters
params = struct('Profile','High','Level','4.0','BitRate',5000000,'FrameRate',vidObj.FrameRate);

% Loop through each video frame
while hasFrame(vidObj)
    
    % Read current frame
    frame = readFrame(vidObj);
    
    % Convert to YCbCr color space
    YCbCr = rgb2ycbcr(frame);
    
    % Split YCbCr into separate components
    Y = YCbCr(:,:,1);
    Cb = YCbCr(:,:,2);
    Cr = YCbCr(:,:,3);
    
    % Perform frame intra prediction on Y component
    Y_pred = intra_prediction(Y);
    
    % Combine YCbCr components
    YCbCr_pred = cat(3,Y_pred,Cb,Cr);
    
    % Convert back to RGB color space
    frame_pred = ycbcr2rgb(YCbCr_pred);
    
    % Write encoded frame to output video
    writeVideo(outputVideo,frame_pred);
end

% Close output video object
close(outputVideo);

function Y_pred = intra_prediction(Y)
    % Block size (8x8)
    block_size = 8;
    
    % Pad input image
    [rows,cols] = size(Y);
    Y_pad = padarray(Y,[block_size-1 block_size-1],'replicate','post');
    
    % Perform intra prediction on each block
    for r = 1:block_size:rows
        for c = 1:block_size:cols
            
            % Get current block
            block = Y_pad(r:r+block_size-1,c:c+block_size-1);
            
            % Calculate prediction mode
            mode = calculate_mode(block);
            
            % Perform prediction
            switch mode
                case 0 % DC mode
                    pred = mean(block(:));
                case 1 % Horizontal mode
                    pred = repmat(block(1,:),[block_size 1]);
                case 2 % Vertical mode
                    pred = repmat(block(:,1),[1 block_size]);
                case 3 % Diagonal mode
                    pred = diag(block);
                    pred = repmat(pred(:),[1 block_size]) + repmat(pred(:)',[block_size 1]);
                    pred = pred/(block_size+1);
                otherwise
                    error('Invalid prediction mode');
            end
            
            % Subtract prediction from current block
            Y_pred(r:r+block_size-1,c:c+block_size-1) = block - pred;
        end
    end
end

function mode = calculate_mode(block)
    % Calculate sum of absolute differences (SAD) for each mode
    SAD = zeros(4,1);
    SAD(1) = sum(abs(block(:)-mean(block(:))));
    SAD(2) = sum(abs(block(1,:)-mean(block(:))));
    SAD(3) = sum(abs(block(:,1)-mean(block(:))));
    SAD(4) = sum(abs(diag(block)-mean(block(:))));
    
    % Find mode with minimum SAD
    [~,mode] = min(SAD);
    mode = mode-1;
end

这段代码实现了一个简单的帧内预测编码器，基于直接模式选择方法（mode selection），并且使用直流、水平、垂直和对角线预测模式进行预测。在实际应用中，需要使用更复杂的编码器和预测算法，以达到更好的压缩效果。