How to record a 60 fps constant frame rate video?

Question

Oscar Cobos 2016-7-7

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/294156-how-to-record-a-60-fps-constant-frame-rate-video

评论： Mariana Alegria Palacios 2024-5-15

I bought a camera that records at 60 and 120 fps and it has set default recording with variable frame rate. I need record at 60 fps constant. If I record setting the following properties the frame rate is variable and lower than 60 fps:

    video = videoinput('winvideo', 1, 'MJPG_800x600');
    % Get the frame rates
    source = getselectedsource(video);
    frameRates = set(source, 'FrameRate')
    % Set the frame rate to 60 fps
    fps = frameRates{1};
    source.FrameRate = fps;
    video.TimeOut = Inf;
    video.TriggerRepeat = Inf;
    video.FrameGrabInterval = 1;
    video.FramesPerTrigger = 1;
    video.LoggingMode = 'disk';
    %%Create the VideoWriter object and set the DiskLogger Property
    timenow = datestr(now,'hhMMss_ddmmyy');
    v = VideoWriter(['video_', timenow,'.avi']);
    v.Quality = 100;
    v.FrameRate = str2double(fps);
    video.DiskLogger = v;

I create a figure with a preview, so I stop recording when the figure is closed.

   start(video)
   uiwait(fig)                                
   stop(video)

I have tried another way based on the example "Creating Time-Lapse Video Using Timer Events" (edit demoimaq_timelapse2):

    function ejemplo_timer_aaaaaaaaaaa()
    %%Creating Time-Lapse Video Using Timer Events
    %
    % This example shows how to create a time-lapse video using timer events to prequalify frames.
    %
    % The Image Acquisition Toolbox(TM) makes it easy to produce time-lapse
    % video.  In this example, we will use timer events to acquire
    % frames to an AVI file.  This technique of time decimation has the
    % advantage that it allows you to make a decision about each frame before
    % storing it. An application of this would be to only store frames that
    % meet certain illumination levels, have motion relative to the previous
    % frame, etc.
    %
    % Copyright 2005-2014 The MathWorks, Inc.
    %%Create a Video Input Object
    % Before acquiring images using the Image Acquisition Toolbox,
    % create a video input object.
    % When executing the following code, you may need to
    % modify it to match your acquisition hardware.
    info = imaqhwinfo('winvideo');
    id = 1;
    formats = info.DeviceInfo(id).SupportedFormats;
    % For windows
    vid = videoinput('winvideo', id, formats{7});
    %%Configure the Timer
    % To generate timer events, we specify two things: what happens when it
    % occurs, and how often it should occur.  The |TimerFcn| property
    % specifies the callback function to execute when a timer event
    % occurs.  A timer event occurs when the time period specified by the
    % |TimerPeriod| property expires.
    %
    % The callback function is responsible for triggering the acquisition and
    % storing the frame into the AVI file. More details on how to use this
    % callback can be found in the documentation.
    % The configuration we will use is
    %
    % * timelapse_timer will execute each time the timer elapses
    % * The timer function will execute every one second
    vid.TimerPeriod = 1/60;
    vid.TimerFcn = @timelapse_timer_v2;
    %%Store the VideoWriter Object
    % Store the VideoWriter object in the |UserData| property of the
    % video input object so that it will be available inside the callback.
    vwObj = VideoWriter('timelapsevideo', 'Uncompressed AVI');
    vwObj.FrameRate = 60;
    open(vwObj);
    vid.UserData = vwObj;
    %%Configure the Video Input Object to Use Manual Triggering
    % Each time the timer event occurs
    %
    % * Manually trigger the acquisition using the |triggerconfig| command
    % * Acquire one frame
    % * Acquire 9 additional triggers worth of data, for a total of 10 frames
    triggerconfig(vid, 'manual');
    vid.FramesPerTrigger = 1;
    vid.TriggerRepeat = 240;
    vid
    %%Perform the Time-Lapse Acquisition
    % Now, start the time lapse acquisition, and wait for up to 20 seconds
    % for the acquisition to complete.
    start(vid);
    % Wait 4 seconds
    wait(vid,4);
    %%Close the AVI File
    % Once the capture is completed, retrieve the VideoWriter object stored in
    % the UserData property, and use the |close| function to release the
    % resources associated with it.
    % vwObj = vid.UserData;
    close(vwObj);
    %%Play Back the Time-Lapse AVI Sequence
    % To play back the time-lapse AVI sequence, right-click on
    % the filename in the MATLAB(R) Current Folder browser, and choose
    % Open Outside MATLAB from the context menu.
    %%Clean Up
    % When you are done with the video input object, you should
    % use the |delete| function to free the hardware resources associated with
    % it, and remove it from the workspace using the |clear| function. Also
    % delete and clear the VideoWriter object.
    delete(vid);
    delete(vwObj);
    clear vid;
    clear vwObj;
    %%The Timer Callback Function
    % The following is a description of the callback function executed for each
    % timer event
    %
    % * Trigger the toolbox to acquire a single frame
    % * Retrieve the frame
    % * Use the |writeVideo| function to add the frame to the AVI file
    %
    % The VideoWriter object is stored in the |UserData| property of the
    % object.
    %
        function timelapse_timer_v2(vid,~)
            % This callback function triggers the acquisition and saves frames to an AVI file.
            tic
            % trigger the acquisition and get the frame
            trigger(vid);
            frame = getdata(vid,1);
            %frame = getsnapshot(vid);       
            % Retrieve the VideoWriter object stored in the UserData
            % property.
            v = vid.UserData;
            % Add the frame to the AVI
            writeVideo(v, frame);
            time = toc
        end
    end

The timer function will be called every 1/60 = 0.016667 seconds, but the comands lines in the function takes to run 0.04 seconds, so it does not works. Any solutions?

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Answer 1

Augusto Sanches 2019-3-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/294156-how-to-record-a-60-fps-constant-frame-rate-video#answer_363932

在 MATLAB Online 中打开

Hello, Oscar!

Would you try that?

clear all
clc
vid1 = videoinput('winvideo', 1);
set(vid1, 'FramesPerTrigger', Inf);
set(vid1, 'ReturnedColorspace', 'rgb')
vid1.FrameGrabInterval = 1;
src1 = getselectedsource(vid1);
frameRates = set(src1, 'FrameRate')
fps = frameRates{1};
src1.FrameRate = fps;
myVideo1 = VideoWriter('cam1.avi');
myVideo1.FrameRate = str2double(fps);
open(myVideo1);
start(vid1);
totalFrames = 150;
while(vid1.FramesAcquired<=totalFrames || vid2.FramesAcquired<=totalFrames)
    img1 = getsnapshot(vid1);
    writeVideo(myVideo1, img1);
end
close(myVideo1);
stop(vid1);
flushdata(vid1);
delete(vid1);

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Mariana Alegria Palacios 2024-5-15

Hi Augusto, I have tried your solution but it generates a video with half the real time, i.e. if you record 60 frames it generates a 1 sec video, but in reality it corresponds to a 2 sec video.

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