Hi Friends,
I am using 16 channels. It says that it gives 125 Sampling rate.
However, when I opened the csv file, it only gives me 50 samples per second. Fyi, I am currently using LSL4UNITY. I am wondering should anyone here has an issue like this before ?
Thanks
Comments
The Daisy sample rate is indeed 125 Hz. Cyton with 8 channels only, is 250 Hz. Have you tried a test using just the 8 channels?
Daisy samples that are streamed over Bluetooth, are processed in a special way:
https://docs.openbci.com/docs/02Cyton/CytonDataFormat#16-channel-data-with-daisy-mdule
In general, LSL streaming is not getting as much support as streaming with direct calls to the appropriate Brainflow library. I also believe there are already other Unity programmers using Brainflow. Which you could find on the Slack.
https://brainflow.org/
Regards, William
I think it is related to the number of frame rate per second. I am now recording the EEG separately instead of streaming the data into UNITY. It gives me 220 sampling rate for 16 channels.... How can it be possible ?
I am using brainflow now
Thanks
https://openbci.com/forum/index.php?p=/discussion/2329/how-steady-is-cytons-sampling-rate-resolved
I still don't get it. After I read the link above. I know that the sampling rate in Cyton is constant for 250 hz, but because of the buffering then it may get a bit lower the moment it arrived in GUI/Hub. I am not using GUI. I just don't understand since you mentioned that for 16 channels, the sampling rate is 125. Why is the sampling rate that I have got is higher than what you mentioned ?
Please re-read the previous link. Sample rate at Cyton is CONSTANT. May differ very slightly from 250.0000 Hz. For example may be 250.0234 Hz. But that is constant and does not change.
What you are seeing as different rate, is due to buffering of samples in the serial usb driver, OS, app, etc.
If you are using Brainflow, then samples are received in that library. The 'Hub' referred to in the previous link is no longer used.
So, referring to 125 Hz. Should I only take the first 125 samples in my data that can be considered for analysis?
I don't quite understand your question. You can select any sample range you wish. Usually EEG samples are correlated with some external environment condition. So you are tracking how the EEG responds to the external situation change.
Sometimes this is done with "external trigger". When the timing has to be very tight and exact, for example P300. But usually the timing constraints are not that exacting. And synchrony with external situation can be measured to the closest second or tenth of a second.
I thought that by using 16 channels it has to give 125 sampling rate. Yet, I am having 222 sampling rate for now.
I am just wondering why I have 222 instead of 125.
Thanks for your explanation
Didn't we cover this with previous comments? How are you measuring the 222 Hz? Using timestamps? The timestamps are assigned when the radio packets are received by the laptop. Thus, they may have considerable delays due to OS scheduling, buffering, usb serial delays, packet retransmission, processor utilization, etc.
The 8 channel sample rate is 250.xxx Hz. The 16 channel, 125.xxx Hz. May differ slightly, but does not jitter. This is termed 'slew' or slight difference from 125.0000. For example may be 125.123. But that stays constant.
William
If you are using Brainflow into Unity, then I suggest you post a question on the Brainflow Slack. I believe I've seen posts there by other successful Unity programmers.
https://brainflow.org/
Yes I am using timestamp.
What I am getting is sometime 222 or some other time 223. Since you mentioned that for 16 channels, 125 Hz, but I have got more. So it does not matter right ?
Once again thanks
I am currently using Brainflow Python
Thanks
Disregard the time stamps. The samples are at a constant rate.
If I disregard the timestamps, then what would be my reference since I need to sync EEG with eye tracker ?
Thanks
https://docs.openbci.com/docs/02Cyton/CytonExternal