OpenViBE forum

The OpenViBE community
It is currently Sun May 26, 2019 11:30 pm

All times are UTC




Post new topic Reply to topic  [ 4 posts ] 
Author Message
 Post subject: Time delays
PostPosted: Wed Apr 17, 2019 9:24 am 
Offline

Joined: Fri May 04, 2018 2:08 pm
Posts: 2
Hi!
I'm running some simulations with OpenViBE and I found out that I have some time delays in my .ov reccorded files.
I converted my .ov file to .mat using the fonction convert_ov2mat that Jussi developed. Then I saw that I have time delays in the time values associeted to each stimulation in the .ov file if I compare them with the time values I get using a Stimulation Listener box in the OV scenario that recorded that file. What is curious is that these delays are not constant.
For the moment I'm not worried about what is generating those delays. But I would like to know if the delays are consistant between stimulations and EEG data. By now, I just can think of trying to show in the console messages the associeted EEG values to each stimulation, in the same way the Stimulation Listener does. Is there any tool that allows me to do that.
Any other ideas are welcome!

Best,

Juliana


Top
 Profile  
Reply with quote  
 Post subject: Re: Time delays
PostPosted: Wed Apr 17, 2019 2:31 pm 
Offline

Joined: Wed Oct 31, 2018 9:14 am
Posts: 79
I'm not sure I understood everything, tell me if I'm wrong :
1 - The conversion between ov and mat does not cause the delay, it was present before
2 - The ov mat have a delay between the stimulation listener
3 - the delay is not regular
4 - In case of delay are random you wan't to show the value on the log at this moment

Can you give me a little stimuluation listener output and the corresponding data.
Have you test to save your acquisition with stimulation in gdf (or csv) and the deay is always here ?


Top
 Profile  
Reply with quote  
 Post subject: Re: Time delays
PostPosted: Fri Apr 26, 2019 1:13 pm 
Offline

Joined: Fri May 04, 2018 2:08 pm
Posts: 2
Hello Thibaut!

Thanks for your answer and feedback!
About the points you mention, I think that you got me right:
1 - You're right. I was just mentioning convert_ov2mat fonction to let you know where my .mat data was coming from.
2 - Yes, the timestamps associated to stimulations in .ov file have delays compared to the timestamps the Stimulation Listener shows.
3 - Yes. If I compare the timestamps I get from the Listener with the ones from the .ov, there is not even one delay value equal to another. They are completely random.
4 - As there are delays, and they are also random, I want to show in the console messages the EEG value associated to each it stimulation the Stimulation Listener gives me.

I saved my simulation in different types of files as you suggested. By now I have just analysed the .csv file. The .csv has time delays as well if I compare it with the Stimulation Listener output.
When compearing between files, the .ov and .csv have different timestamps for the stimulations but I observed that those delays are more regular (there isn't a constant delay, but some delay values are repeated).
What I found interesting when analizing the .csv file is that there are two timestamps associated to each stimulation. If I understood well, the time values that we have in the first column corresponds to the sampling time, i.e. the time associated to each EEG sample. Then the time values that we have in the column corresponding to Event Date, are the real time values associated to the stimulation. And then, each stimulation is associated to the previous receibed data chunck. I hope I'm being clear enough.

I attach the Stimulation Listener output and the scenario I used to generate them. I can't upload the .ov and .csv because the limit is 256kb. In the .txt file it is shown the output of two different listener, one from the Lua Stimulator box that is generating the stimulations, and the other from the Acquisition client.

Best,

Juliana


Attachments:
TestDelays.7z [3.3 KiB]
Downloaded 4 times
Top
 Profile  
Reply with quote  
 Post subject: Re: Time delays
PostPosted: Mon Apr 29, 2019 10:14 am 
Offline

Joined: Wed Oct 31, 2018 9:14 am
Posts: 79
Hi Julianna,
If you sort the line by box you can see the delay is always 0,008 s for the box Graz (with lua it's normal).
The Acquisition Client can have random delay around 100ms (if you check the acquisition server you can see this delay (with the green bar).
If the time is different in ov file I don't know yet why, I'm going to search.
Thibaut


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group
Americanized by Maƫl Soucaze.