Getting lossless images from mjpeg

I am learning with video to image conversion and vice versa.

I had a mjpeg of 3 sec, when i converted to jpeg images i got 55 images.

then i used all 55 images to make a mjpeg video but the video is not of 3 sec anymore

Please tell me correct way of video to image conversion and vice versa. i am not getting where i am going wrong.

Answer 1

[Varsha Nataraj]

hello iqra,

i am very sorry for not replying so long.

i cleared my issue after refering to this link below

https://in.mathworks.com/help/matlab/examples/convert-between-image-sequences-and-video.html

go through this

hope it helps

[Iqra Saleem]

Can you tell me from where you get motion jpeg video.

I tried to convert using Oxelon media Converter but that .mjpg video is not playing in matlab.

[Varsha Nataraj]

it will be in .avi format

Answer 2

[Walter Roberson]

It is impossible to get lossless images from Motion JPEG. mjpeg inherently uses lossy jpeg compression .

However it sounds to me as if you did not tell the video writer that the frame rate should be 55/3 frames per second. (I suspect your real frame rate is either 18 or 20 fps and that 3 seconds is an approximation )

[Varsha Nataraj]

https://in.mathworks.com/help/matlab/examples/convert-between-image-sequences-and-video.html

this link has details

Answer 3

[Iqra Saleem]

Hey;

Varsha Natraj , can you tell me please how you convert motion jpeg to jpeg images?

[Walter Roberson]

Use VideoReader (basic MATLAB) or vision.VideoFileReader (Computer Vision Toolbox) to read frame by frame from the motion JPEG file, and imwrite() each frame to a file.

[Iqra Saleem]

Thanks for your reply , i am using VideoReader in matlab but this error appear.

Error using VideoReader/init (line 619)

Unable to determine the codec required.

my video is motion jpeg with .mjpeg extension

[Walter Roberson]

See https://www.mathworks.com/matlabcentral/answers/218237-unable-to-determine-the-codec-required#answer_180148

[Iqra Saleem]

i am not getting your point. kindly help me, I want to read motion jpeg video in matlab but this error occurs:

Error using VideoReader/errorIfImageFormat (line 494)

The filename specified is an image file. Use imread instead of VideoReader.

Error in VideoReader/init (line 612) VideoReader.errorIfImageFormat(fullName);

Error in Untitled2 (line 5)

xyloObj = VideoReader('akiyo_CIF.mjpg');

[Iqra Saleem]

My matlab code is :

clc
close all
clear all
info = mmfileinfo('akiyo_CIF.mjpg');
xyloObj = VideoReader('akiyo_CIF.mjpg');
get(xyloObj)
nFrames = xyloObj.NumberOfFrames;
vidHeight = xyloObj.Height;
vidWidth = xyloObj.Width;
% Preallocate movie structure.
mov(1:nFrames) = ...
    struct('cdata', zeros(vidHeight, vidWidth, 3, 'uint8'),...
           'colormap', []);
% Read one frame at a time.
for k = 1 : 3
    mov(k).cdata = read(xyloObj, k);
end
% Size a figure based on the video's width and height.
hf = figure;
set(hf, 'position', [150 150 vidWidth vidHeight])
% Play back the movie once at the video's frame rate.
movie(hf, mov, 1, xyloObj.FrameRate);

[Walter Roberson]

Except possibly on Linux, .mpeg or .mjpg is not a supported video format. Motion JPEG is supported inside of .avi

https://www.mathworks.com/help/matlab/import_export/supported-video-file-formats.html