Handling Large Video Files

Hello!

I am currently making program that pulls specific frames from a large video. I have found that loading the video file into the Matlab workspace drastically speeds up the process. However, because the files are large, I receive an error stating that there is not enough memory to open all of the frames. The video is 9min 45sec long, but I want to be able to handle even larger files, on the order of an hour+. Is there any way for Matlab to open these kinds of matrices its workspace?

Also, feel free to let me know if I am going about this the wrong way.

The idea is to create a function such that when it is called, it quickly (hopefully >>10sec) opens part of a video and plays a short clip of it,

For your reference, here are 2 versions of the code

Version 1: The file does not need to be in the workspace, but it is limited by the Java Heap Space available.

function [] = videoPlayer(file1, interval, hour, min, sec)
%Plays the video around a selected frame
% file1 denotes the name of the movie file. User MUST include file
% extension (.mp4, .avi, .mov etc)
% interval denotes how many seconds around selected frame to play
% hour, min, sec denote which frame user would like to select

video = VideoReader(file1);
nFrames = video.NumberOfFrames;
vidHeight = video.Height;
vidWidth = video.Width;
fps = round(video.FrameRate);

time = hour*3600 + min*60 + sec;

frameSelected = fps*time;
initial = frameSelected-(interval*fps);
final = frameSelected+(interval*fps);
frameNum = final-initial;

mov(1:frameNum) = struct ('cdata', zeros(vidHeight, vidWidth, 3, 'uint8'), 'colormap', []);

for i = 1:frameNum
    mov(i).cdata= read(video,((initial-1)+i));
end

hf = figure;
set(hf, 'position', [150 150 vidWidth vidHeight]);

movie (hf,mov,1,fps);

end

Version 2: Where you take info from the file itself, and from the array loaded into the Matlab workspace.

function [] = videoPlayer2(file1, video1, interval, hour, min, sec)
%Plays the video around a selected frame
% file1 denotes the name of the movie file. User MUST include file
% extension (.mp4, .avi, .mov etc)
% video1 is file1 opened in Matlab workspace
% interval denotes how many seconds around selected frame to play
% hour, min, sec denote which frame user would like to select

video = VideoReader(file1);
nFrames = video.NumberOfFrames;
vidHeight = video.Height;
vidWidth = video.Width;
fps = round(video.FrameRate);

time = hour*3600 + min*60 + sec;

frameSelected = fps*time;
initial = frameSelected-(interval*fps);
final = frameSelected+(interval*fps);
frameNum = final-initial;

mov(1:frameNum) = struct ('cdata', zeros(vidHeight, vidWidth, 3, 'uint8'), 'colormap', []);

for i = 1:frameNum
    mov(i).cdata= video1 (:,:,:,((initial-1)+i));
end

hf = figure;
set(hf, 'position', [150 150 vidWidth vidHeight]);

movie (hf,mov,1,fps);

end

[per isakson]

My first thought: memmapfile, Create memory map to a file