How can I save the video file from matlab videoPlayer

Question

shinnosuke kurahashi 2019-12-4

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/494742-how-can-i-save-the-video-file-from-matlab-videoplayer

回答： Walter Roberson 2019-12-4

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

How can I save the video file from matlab videoPlayer? I want to export the processed video

https://jp.mathworks.com/help/vision/examples/video-stabilization-using-point-feature-matching.html.

The file could be saved, but the file cannot be opened.If you try to open it, you will get an error with a message like this.

"The file cannot be played. The file format for this item may not be supported, the file extension may be incorrect, or the file may be corrupted."

filename = 'W1Film1_0-30s.avi';
hVideoSrc = vision.VideoFileReader(filename, 'ImageColorSpace', 'Intensity');
imgA = step(hVideoSrc); % Read first frame into imgA
imgB = step(hVideoSrc); % Read second frame into imgB
figure; imshowpair(imgA, imgB, 'montage');
title(['Frame A', repmat(' ',[1 70]), 'Frame B']);
figure; imshowpair(imgA,imgB,'ColorChannels','red-cyan');
title('Color composite (frame A = red, frame B = cyan)');
ptThresh = 0.1;
pointsA = detectFASTFeatures(imgA, 'MinContrast', ptThresh);
pointsB = detectFASTFeatures(imgB, 'MinContrast', ptThresh);
% Display corners found in images A and B.
figure; imshow(imgA); hold on;
plot(pointsA);
title('Corners in A');
figure; imshow(imgB); hold on;
plot(pointsB);
title('Corners in B');
% Extract FREAK descriptors for the corners
[featuresA, pointsA] = extractFeatures(imgA, pointsA);
[featuresB, pointsB] = extractFeatures(imgB, pointsB);
indexPairs = matchFeatures(featuresA, featuresB);
pointsA = pointsA(indexPairs(:, 1), :);
pointsB = pointsB(indexPairs(:, 2), :);
figure; showMatchedFeatures(imgA, imgB, pointsA, pointsB);
legend('A', 'B');
[tform, pointsBm, pointsAm] = estimateGeometricTransform(...
    pointsB, pointsA, 'affine');
imgBp = imwarp(imgB, tform, 'OutputView', imref2d(size(imgB)));
pointsBmp = transformPointsForward(tform, pointsBm.Location);
figure;
showMatchedFeatures(imgA, imgBp, pointsAm, pointsBmp);
legend('A', 'B');
% Extract scale and rotation part sub-matrix.
H = tform.T;
R = H(1:2,1:2);
% Compute theta from mean of two possible arctangents
theta = mean([atan2(R(2),R(1)) atan2(-R(3),R(4))]);
% Compute scale from mean of two stable mean calculations
scale = mean(R([1 4])/cos(theta));
% Translation remains the same:
translation = H(3, 1:2);
% Reconstitute new s-R-t transform:
HsRt = [[scale*[cos(theta) -sin(theta); sin(theta) cos(theta)]; ...
  translation], [0 0 1]'];
tformsRT = affine2d(HsRt);
imgBold = imwarp(imgB, tform, 'OutputView', imref2d(size(imgB)));
imgBsRt = imwarp(imgB, tformsRT, 'OutputView', imref2d(size(imgB)));
figure(2), clf;
imshowpair(imgBold,imgBsRt,'ColorChannels','red-cyan'), axis image;
title('Color composite of affine and s-R-t transform outputs');
% Reset the video source to the beginning of the file.
reset(hVideoSrc);
                      
hVPlayer = vision.VideoPlayer; % Create video viewer
% Process all frames in the video
movMean = step(hVideoSrc);
imgB = movMean;
imgBp = imgB;
correctedMean = imgBp;
ii = 2;
Hcumulative = eye(3);
while ~isDone(hVideoSrc) && ii <30 % 1200
    % Read in new frame
    imgA = imgB; % z^-1
    imgAp = imgBp; % z^-1
    imgB = step(hVideoSrc);
    movMean = movMean + imgB;
    % Estimate transform from frame A to frame B, and fit as an s-R-t
    H = cvexEstStabilizationTform(imgA,imgB);
    HsRt = cvexTformToSRT(H);
    Hcumulative = HsRt * Hcumulative;
    imgBp = imwarp(imgB,affine2d(Hcumulative),'OutputView',imref2d(size(imgB)));
    % Display as color composite with last corrected frame
    step(hVPlayer, imfuse(imgAp,imgBp,'ColorChannels','red-cyan'));
    correctedMean = correctedMean + imgBp;
    result = correctedMean;
    videoReader = hVideoSrc;
    videoFWriter=vision.VideoFileWriter('result.avi','FrameRate',videoReader.info.VideoFrameRate);
    step(videoFWriter,result);  % saves video
    
    ii = ii+1;
end
correctedMean = correctedMean/(ii-2);
movMean = movMean/(ii-2);
% Here you call the release method on the objects to close any open files
% and release memory.
release(hVideoSrc);
release(hVPlayer);
figure; imshowpair(movMean, correctedMean, 'montage');
title(['Raw input mean', repmat(' ',[1 50]), 'Corrected sequence mean']);

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Answer 1

Walter Roberson 2019-12-4

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/494742-how-can-i-save-the-video-file-from-matlab-videoplayer#answer_404653

在 MATLAB Online 中打开

    videoFWriter=vision.VideoFileWriter('result.avi','FrameRate',videoReader.info.VideoFrameRate);

You have that line inside the loop, so you are creating a new VideoFileWriter each iteration. You should be doing that line once before the loop.

With your current situation, you are ending up with a video that contains a single frame in it. I have seen in the past that a minimum of two frames are needed in some video formats for the video to be considered valid.