A possible method of importing a video in to the PIVlab GUI without using DaVis

[Billy]

Hi, William

I spoke to you the other day about a possible method of importing a video into the gui without using DaVis. Would you possibly have any suggestion? If this is not possible, do you have any suggestions on the most accurate way of analysing my results? Could this be to split the video into several images and perform the analysis as demonstrated in your tutorial? Attached is the data I am working with. 

Thankyou 

Billy 

[William Thielicke]

Hi Billy, yes just convert this to image files. However, the video quality is very bad with lots of compression artifacts and poor resolution, so you need to choose suitable parameters.

[billyb...@gmail.com]

Okay thank you!

So it may be advisable to take some better quality footage if I want my analysis to be more accurate?

Also one more thing, If I am analysing similar footage that is of a significantly higher frequency and manage to split that into images, will the PIV lab tool be able to differentiate this difference and provide me with the increased output values. E.g. I would expect the velocity magnitude to be greater when the oscillation frequency is greater. 

Thanks  

[William Thielicke]

Hi,

yes, you need better footage. Especially noise and compression need to be low. You should also pay attention to zooming in to the region of your interest. What frame rate and resolution are you currently recording with? Typical PIV recordings that I worked with had between 500 and 2000 fps at full HD.

And yes, if your velocity is higher, then PIVlab will accurately measure that.

Here is an example that uses video footage that is a little bit similar to yours:

https://pivlab.blogspot.com/2018/05/slow-motion-of-clothes-in-drying-machine.html

[billyb...@gmail.com]

Hi,

Okay I will try and take some better quality footage. I only have access to an iPhone 7 therefore my framerate and resolution is limited. I think its around 250 fps and 1334x750 resolution. Will that be suitable to obtain some results?  

[William Thielicke]

Hi,
Yes "some results" is the correct wording ;). Don't blame PIVlab if you are unhappy with the results, it is only as good as the images.

[b.walki...@gmail.com]

Hi William I have used piv lab and it

appears to give me some reasonable results. I wondered whether it is possible for me to obtain data of the sand/rubber particles relative to the box. What I mean by this is effectively zeroing the movement of the box in my video and obtaining data specifically of the particles. Is this possible?

Thank you for your time

Chat conversation end

Type a message...

[William Thielicke]

You can measure the velocity of the box in PIVlab, and then subtract that velocity from the rest in PIVlab.