How to get file (video) from PSNR on the video compression?

I am a student

I have a project fro my lecturer to analyze video compression. I don't know how to get file (video) from the variable video compression (PSNR).

can anyone help me?

thank you

Answer 1

[Walter Roberson]

You cannot do that. Psnr is a statistical measure. You cannot recover the image from it.

[Joni Afria]

PSNR is a comparison between input and output files. I already got PSNR, but I have trouble to get the output file.

[Walter Roberson]

It is not possible to work backwards from psnr to compressed image.

For some kinds of compression if you were given an original image and a target psnr then it would be possible to construct a compressed image with that psnr.

[Joni Afria]

I get the matlab code from here

https://www.mathworks.com/matlabcentral/fileexchange/55901-h-264-baseline-codec-v2

[Walter Roberson]

There are 32 or so functions in that contribution. You need to be more specific.

[Joni Afria]

% *************************************************************************
%% H.264/AVC DECODER
% It works on YUV sequence
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% This script/function was created by
% Abdullah Al Muhit
% contact - Almuhit [At] Gmail.com
% website - https://sites.google.com/site/almuhit/
% Please use it at your own risk. Also, Please cite the following paper:
% A A Muhit, M R Pickering, M R Frater and J F Arnold, “Video Coding using Elastic Motion Model and Larger Blocks,” IEEE Trans. Circ. And Syst. for Video Technology, vol. 20, no. 5, pp. 661-672, 2010. [Impact factor – 3.18] [PDF]
% A A Muhit, M R Pickering, M R Frater and J F Arnold, “Video Coding using Geometry Partitioning and an Elastic Motion Model,” accepted for publication in Journal of Visual Communication and Image Representation. [Impact factor – 1.33] [PDF]
% Modification is done by Ali Radmehr
% Feel free to contact us: Radmehr.Telecom [AT] Gmail.Com
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Initialization
clear all;
clc;
close all;
tic
system_dependent('DirChangeHandleWarn', 'Never');
addpath(genpath('.'));

%% Input - load the encoded file

load ./bitstream_enc.mat; % correct packets

global h w QP block_size

%%%%%%%%%%%%%%%%%%%%
Frame_start = 20;        % I frame
Frame_end = 25;          % Following P frames
FrameNo = 1+(Frame_end-Frame_start);
%%%%%%%%%%%%%%%%%%%%
width = 176;
height = 144;
[mov,imgRgb] = loadFileYuv('suzie_qcif.yuv',width,height,Frame_start:Frame_end); % loading yuv file
mov_yuv = zeros(height,width,3,FrameNo); % (h,w,y/u/v,number of frames!!
% Deviding yuv components.
% Just y component is needed!
mov_y = zeros(height,width,FrameNo);
for i =1:FrameNo
    mov_yuv(:,:,:,i) = double(mov(i).cdata);
    mov_y(:,:,i) = mov_yuv(:,:,1,i);
end
%-------------------------
idx = 1;
block_size = 16; % change blocksize if needed!

%---------------------------------------------------------
% Decode header
[h,w,QP,Frame_start,Frame_end,m] = dec_header(bitstream);
idx = idx + m - 1;

N = 1 + (Frame_end - Frame_start);

if (strcmp(bitstream(idx:idx+3),'1111'))
    disp('Decoding I Frame')
    idx = idx + 4;
    [Ceq_r(:,:,1),idx]=decode_i_frame(idx,bitstream);
    
    Ceq(:,:,1) = mov_y(:,:,1);
    PSNR_rec(1)=find_psnr(Ceq(:,:,1),Ceq_r(:,:,1));
    PSNR_rec_ec(1)=find_psnr(Ceq(:,:,1),Ceq_r(:,:,1));
end

Ceq_r_ec(:,:,1) = Ceq_r(:,:,1);
figure(1)
pause(1)
image(Ceq_r_ec(:,:,1))
title(['Frame No. ' num2str(Frame_start)]);
colormap(gray(256))
truesize([2*h 2*w])
drawnow
for k = 2:N
    if (strcmp(bitstream(idx:idx+3),'0000'))
        disp('Decoding P Frame')
        idx = idx + 4;
        
        %-----------PERFORMING EC ON THE ERRONEOUS FRAME---------------
        B=0; %1.4; % Average Burst Length
        PLR=0; %5/100; % Packet Loss Rate
        [Ceq_r_ec(:,:,k),idx,ErrorMat]= decode_p_frame(idx,bitstream,Ceq_r_ec(:,:,k-1),B,PLR); % decoding using ec
        if isempty(ErrorMat) == 0 % if there is any error, EC would be applied.
            Ceq_r_ec(:,:,k) = EC(Ceq_r_ec(:,:,k),Ceq_r_ec(:,:,k-1),ErrorMat,1,block_size); %mode 1 is frame-copy method.
        end
        % visualizing the decoded frame with error concealment
        figure(1)
        image(Ceq_r_ec(:,:,k))
        title(['Frame No. ' num2str(Frame_start+k-1)]);
        colormap(gray(256))
        truesize([2*h 2*w])
        drawnow
        pause(1)
        
        %--------------------------------------------------------------
        
        Ceq(:,:,k) = mov_y(:,:,k);
        %PSNR_rec(k) = find_psnr(Ceq(:,:,k),Ceq_r(:,:,k));
        PSNR_rec_ec(k) = find_psnr(Ceq(:,:,k),Ceq_r_ec(:,:,k));
    end
    
end
% disp(['average PSNR without any error concealment is: ', num2str(mean(PSNR_rec))])
disp([ 'average PSNR with frame-copy error concealment is: ', num2str(mean(PSNR_rec_ec))])
toc

[Joni Afria]

Mr @walter roberson

Now i can recontruct video from the code https://www.mathworks.com/matlabcentral/fileexchange/55901-h-264-baseline-codec-v2

but, now i have new problem, the video just play one frame for 5 second. Can you help me Mr?