OpenViBE forum

The OpenViBE community
It is currently Wed Jun 20, 2018 6:00 am

All times are UTC

Post new topic Reply to topic  [ 2 posts ] 
Author Message
PostPosted: Tue Apr 11, 2017 3:44 pm 

Joined: Tue Apr 11, 2017 10:44 am
Posts: 24
I want to know if this is how the time epoch box works in the spaceship scenario . and I have 2 questions :

1 . how does the time epoching work in conjunction with the average box ? after bandpassing the input stream we have a time epoching box which I think works like this (assuming we epoch duration is 0.3 sec and epoch interval is 0.1 sec and assuming that xi is a vector):

time(msec) : 1 2 3 4 5 6

input : x1 x2 x3 x4 x5 x6

output : x1 x2 x3 x2 x3 x4 ...

now assume we give this output to the average box.

it's documentation says :

"This plugin computes the average of each incoming sample buffer and outputs the resulting signal."

"The output signal's sample count per channel per buffer is one, since a buffer contains the averages (per channel) of the values of an input buffer. "

so by epoching the signal we have increased the buffer size ? and now the average is computed over 3 vectors rather than 1 ?

also the output of the average would be the average of vectors x1 , x2 ,x3 from 0.1 to 0.2 then average of x2,x3,x4 from 0.2 to 0.3 ? is this correct ?

2. in the spaceship scenario is it necessary to epoch the signal before giving it to the DSP box with the formula "x*x" ?
as I understand "x*x" just squares the elements of the vectors in our stream . so epoching should not have an effect on it .

p.s sorry if my questions are naive !

Reply with quote  
PostPosted: Fri May 05, 2017 7:26 am 

Joined: Tue Dec 04, 2012 3:53 pm
Posts: 705
Location: INRIA Rennes, FRANCE
Hi Kiyarash,

without going into the details, if you ask epoch of 5 seconds, one buffer will contain 5 seconds worth of samples. You can imagine a sliding window of that size taking snapshots of the data with the window 'stepping forward' by the amount of time specified by the interval. The output of the box are these 'snapshots'.

The average is computed from whatever samples are in each received buffer.

Finally, although you can use simple dsp at any point, there can be a difference between E[xx] and E[x]E[x]: you need to decide if you average squares or square averages.


Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2 posts ] 

All times are UTC

Who is online

Users browsing this forum: No registered users and 3 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:  
Powered by phpBB® Forum Software © phpBB Group
Americanized by Maƫl Soucaze.