reading tf data from ROSBAG is way to slow

Question

Robin 2017-11-6

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https://ww2.mathworks.cn/matlabcentral/answers/365369-reading-tf-data-from-rosbag-is-way-to-slow

评论： MathWorks Robotics and Autonomous Systems Team 2017-12-5

I would like to get all tf data the whole run in a rosbag using a timeseries or struc object.

for i = 1:1000:tfselection.NumMessages      
    transformdata =cellfun(@(x) x.Transforms,   readMessages(tfselection, [i:min(i+999,tfselection.NumMessages)]), 'UniformOutput', 0);
        for im = 1:numel(transformdata)
            for tfm = 1:numel(transformdata{im})                           
                tt = transformdata{im}(tfm);                           
                messages(index, :) = {tt.Header.Stamp.Sec + tt.Header.Stamp.Sec/10^9, tt.Header.FrameId, tt.ChildFrameId, tt.Transform.Translation, tt.Transform.Rotation};
                index = index+1;   
             end   
             disp(['at ' num2str(im + i) ' from ' num2str(tfselection.NumMessages) ' msgs - containing ' num2str(index) ' msgs']);
        end     
end

since i was running out of java heap i access the messages in steps.

Without any perfomance boost I already tried

calling transformdata{im}(tfm).copy()
calling transformdata{im}(tfm).toStruc()
calling exthead = tt.header and using exthead.Stamp... etc..

Now I would like to use the vectorising functions like structfun and cell fun but unfortunately Im not quite sure how to implement these in this case.

Is this the fastest solution and can someone give me an hint please?

transformdata

1000x1 cell containing Nx1 TansformStamped where n can vary

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Robin 2017-11-7

编辑：Robin 2017-11-7

在 MATLAB Online 中打开

After a deeply debugging session I found out that the get method from the Message Classes costs the most time:

    classdef TransformStamped < robotics.ros.Message
    [...]
    if isempty(obj.Cache.Header)
         obj.Cache.Header = feval(obj.StdMsgsHeaderClass, obj.JavaMessage.getHeader);
    end
    header = obj.Cache.Header;
    [...]
    end

unfortunalety i don't dont have acces to these classes and I'm running out of options.

In HERE is briefly explained how to increase speed with slow java classes but nothing is giving me any boost.

Is there another way to read rosbag data without using java?

MathWorks Robotics and Autonomous Systems Team 2017-12-5

Sorry for the delay in responding, in couple of weeks the R2018a Prerelease version is going to be out on mathworks.com, I strongly recommend you to try the latest "rosbag" and TF extraction functionality.

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reading tf data from ROSBAG is way to slow

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