I am having trouble understanding latency in the context of eye-tracking. I currently work with a 30Hz eye-tracker integrated into a head-mounted display for vision research.
The way I look at it, there is an overall delay in the time when the eye actually makes a movement to the time these coordinates are provided by the eye-tracking software. There are two components to this delay ->
1) The delay because of the frequency of imaging by the eye tracker (30fps -- 33.3ms)
2) The latency because of the actual algorithm that extracts data and provides coordinates.
Am I right in thinking that the total delay is the sum of 1) and 2) ?
I spoke with the company that makes the eye-tracker, and they said the latency in eye tracking is 60ms. Does that mean that my overall latency is 60ms + (1000/30Hz) ~ 93.3ms ?
Or does the 60ms figure somehow take into account the FPS of the eye camera?
Different vendors use different definitions of eye tracking latency so you have to ask your specific vendor what definition they use when they state 60 ms latency.
As an example Tobii, one of the largest eye tracking vendors, uses the following definitions:
Processing latency: Describes the time required by the eye tracker processor to perform image processing and eye gaze computations.
Total system latency: The duration from mid-point of the eye image exposure, to when a sample is available via the API on the client computer. This includes half of the image exposure time, plus image read-out and transfer time, processing time and time to transfer the data sample to a client computer.
I would assume that the number the company gave you 60ms is the total latency of everything. This is assuming that they are the ones providing the software and the camera.
If the cameras latency is not included then your calculation for the latency should be correct.
Related
Currently I'm building my monitoring services for my e-commerce Server, which mostly focus on CPU/RAM usage. It's likely Anomaly Detection on Timeseries data.
My approach is building LSTM Neural Network to predict next CPU/RAM value on chart trending and compare with STD (standard deviation) value multiply with some number (currently is 10)
But in real life conditions, it depends on many differents conditions, such as:
1- Maintainance Time (in this time "anomaly" is not "anomaly")
2- Sales time in day-off events, holidays, etc., RAM/CPU usages increase is normal, of courses
3- If percentages of CPU/RAM decrement are the same over 3 observations: 5 mins, 10 mins & 15 mins -> Anomaly. But if 5 mins decreased 50%, but 10 mins it didn't decrease too much (-5% ~ +5%) -> Not an "anomaly".
Currently I detect anomaly on formular likes this:
isAlert = (Diff5m >= 10 && Diff10m >= 15 && Diff30m >= 40)
where Diff is Different Percentage in Absolute value.
Unfortunately I don't save my "pure" data for building neural network, for example, when it detects anomaly, I modified that it is not an anomaly anymore.
I would like to add some attributes to my input for model, such as isMaintenance, isPromotion, isHoliday, etc. but sometimes it leads to overfitting.
I also want to my NN can adjust baseline over the time, for example, when my Service is more popular, etc.
There are any hints on these aims?
Thanks
I would say that an anomaly is an unusual outcome, i.e. a outcome that's not expected given the inputs. As you've figured out, there are a few variables that are expected to influence CPU and RAM usage. So why not feed those to the network? That's the whole point of Machine Learning. Your network will make a prediction of CPU usage, taking into account the sales volume, whether there is (or was) a maintenance window, etc.
Note that you probably don't need an isPromotion input if you include actual sales volumes. The former is a discrete input, and only captures a fraction of the information present in the totalSales input
Machine Learning definitely needs data. If you threw that away, you'll have to restart capturing it. As for adjusting the baseline, you can achieve that by overweighting recent input data.
My Mera VoIP Transit Softswitch (MVTS) shows very low ACD (about 0.3 min) for several directions (route groups) at peak hours. Looking for factors causing low ACD, I foung this topic: http://support.sippysoft.com/support/discussions/topics/3000137333, but all mentioned parameters seem to be normal. There is another strange thing also. As seen at this graph, there are about 10 lines occupied for each real call. I guess these problems are related somehow, though not sure yet.
What can cause such behavior?
You should check the followings:
SIP trunk quality
Your trunk or service providers might have quality issues to these directions. You can easily test this by sending the same traffic in the same time to some other carriers.
Low call quality under high load
You can easily verify this by just making a call during peak time and hear it yourself.
Some other factor causing call drop in similar circumstances.
Causes might include maximum supported channels, billing cut-off or others.
You should grab a statistics about disconnect codes and compare it to off-peak time or to other directions
I have a project that consisted of transmitting data wirelessly from 15 tractors to a station, the maximum distance between tractor and station is 13 miles. I used a raspberry pi 3 to collect data from tractors. with some research I found that there is no wifi or GSM coverage so the only solution is to use RF communication using VHF. so is that possible with raspberry pi or I must add a modem? if yes, what is the criterion for choosing a modem? and please if you have any other information tell me?
and thank you for your time.
I had a similar issue but possibly a little more complex. I needed to cover a maximum distance of 22 kilometres and I wanted to monitor over 100 resources ranging from breeding stock to fences and gates etc. I too had no GSM access plus no direct line of sight access as the area is hilly and the breeders like the deep valleys. The solution I used was to make my own radio network using cheap radio repeaters. Everything was battery operated and was driven by the receivers powering up the transmitters. This means that the units consume only 40 micro amps on standby and when the transmitters transmit, in my case they consume around 100 to 200 milliamps.
In the house I have a little program that transmits a poll to the receivers every so often and waits for the units to reply. This gives me a big advantage because I can, via the repeater trail (as each repeater, the signal goes through, adds its code to the returning message) actually determine were my stock are.
Now for the big issue, how long do the batteries last? Well each unit has a 18650 battery. For the fence and gate controls this is charged by a small 5 volt solar panel and after 2 years running time I have not changed any of them. For the cattle units the length of time between charges depends solely on how often you poll the units (note each unit has its own code) with one exception (a bull who wants to roam and is a real escape artist) I only poll them once or twice a day and I swap the battery every two weeks.
The frequency I use is 433Mhz and the radio transmitters and receivers are very cheap ( less then 10 cents a pair if you by them in Australia) with a very small Attiny (I think) arduino per unit (around 30 cents each) and a length on wire (34.6cm long as an aerial) for the cattle and 69.2cm for the repeaters. Note these calculations are based on the frequency used i.e. 433Mhz.
As I had to install lots of the repeaters I contacted an organisation in China (sorry they no longer exist) and they created a tiny waterproof and rugged capsule that contained everything, while also improving on the design (range wise while reducing power) at a cost of $220 for 100 units not including batterys. I bought one lot as a test and now between myself and my neighbours we bought another 2000 units for only $2750.
In my case this was paid for in less then three months when during calving season I knew exactly were they were calving and was on site to assist. The first time I used it we saved a mother who was having a real issue.
To end this long message I am not an expert but I had an idea and hired people who were and the repeater approach certainly works over long distances and large areas (42 square kilometres).
Following on from the comments above, I'm not sure where you are located but spectrum around the 400mhz range is licensed in many countries so it would be worth checking exactly what you can use.
If this is your target then this is UHF rather than VHF so if you search for 'Raspberry PI UHF shield' or 'Raspberry PI UHF module' you will find some examples of cheap hardware you can add to your raspberry pi to support communication over these frequencies. Most of the results should include some software examples also.
There are also articles on using the pins on the PI to transmit directly by modulating the voltage them - this is almost certainly going to interfere with other communications so I doubt it would meet your needs.
Is there a way to calculate the electricity consumed to load and render a webpage (frontend)? I was thinking of a 'test' made with phantomjs for example:
load a web page
scroll to the bottom
And measure how much electricity was needed. I can perhaps extrapolate from CPU cycle. But phantomjs is headless, rendering in real browser is certainly different. Perhaps it's impossible to do real measurements.. but with an index it may be possible to compare websites.
Do you have other suggestions?
It's pretty much impossible to measure this internally in modern processors (anything more recent than 286). By internally, I mean by counting cycles. This is because different parts of the processor consume different levels of energy per cycle depending upon the instruction.
That said, you can make your measurements. Stick a power meter between the wall and the processor. Here's a procedure:
Measure the baseline energy usage, i.e. nothing running except the OS and the browser, and the browser completely static (i.e. not doing anything). You need to make sure that everything is stead state (SS) meaning start your measurements only after several minutes of idle.
Measure the usage doing the operation you want. Again, you want to avoid any start up and stopping work, so make sure you start measuring at least 15 seconds after you start the operation. Stopping isn't an issue since the browser will execute any termination code after you finish your measurement.
Sounds simple, right? Unfortunately, because of the nature of your measurements, there are some gotchas.
Do you recall your physics classes (or EE classes) that talked about signal to noise ratios? Well, a scroll down uses very little energy, so the signal (scrolling) is well in the noise (normal background processes). This means you have to take a LOT of samples to get anything useful.
Your browser startup energy usage, or anything else that uses a decent amount of processing, is much easier to measure (better signal to noise ratio).
Also, make sure you understand the underlying electronics. For example, power is VA (voltage*amperage) where both V and A are in phase. I don't think this will be an issue since I'm pretty sure they are in phase for computers. Also, any decent power meter understands the difference.
I'm guessing you intend to do this for mobile devices. Your measurements will only be roughly the same from processor to processor. This is due to architectural differences from generation to generation, and from manufacturer to manufacturer.
Good luck.
Hi,
In the CDMA cellular networks when MS (Mobile Station) need to change a BS(Base Station), exactly necessary for hand-off, i know that is soft hand-off (make a connection with a target BS before leaving current BS-s). But i want to know, because connection of MS remaining within a time with more than one BS, MS use the same code in CDMA to communicate with all BS-s or different code for different BS-s ?
Thanks in advance
For the benefit of everyone, i have touched upon few points before coming to the main point.
Soft Handoff is also termed as "make-before-break" handoff. This technique falls under the category of MAHO (Mobile Assisted Handover). The key theme behind this is having the MS to maintain a simultaneous communication link with two or more BS for ensuring a un-interrupted call.
In DL direction, it is achieved using different transmission codes(transmit same bit stream) on different physical channels in the same frequency by two or more BTS wherein the CDMA phone simultaneously receives the signals from these two or more BTS. In the active set, there can be more than one pilot as there could be three carriers involved in soft hand off. Also, there shall also be a rake receiver that shall do maximal combining of received signals.
In UL direction, MS shall operate on a candidate set where there could be more than 1 pilot that have sufficient signal strength for usage as reported by MS. The BTS shall tag each of the user's data with Frame reliability indicator that can provide details about the transmission quality to BSC. So, even though the signals(MS code channel) are received by both base stations, it is achieved by routing the signals to the BSC along with information of quality of received signals, which shall examine the quality based on the Frame reliability indicator and choose the best quality stream or the best candidate.