I would like to have an idea of the "network quality" from my app to adapt the user experience.
I know that it is possible to know if connection is WIFI or WWAN (EDGE/3G)... but it seems not possible to make the difference between 3G and edge...
My idea is to "test the connection" by computing latency and download rate.
Before make the library myself, is thee available library for that ?
Of course I need to use "official solution" without using private APIs...
There's no lib AFAIK, because it's a very complex problem. If you were to only calculate the download speed, how would you compare this to the app responsiveness ? The latter is eventually what is important to the user; download speed is only one factor in a more complex equation. Also, how would you react to temporary network disruptions or slugginess ? (fairly common on Mobile network), they do not necessarily imply a fallback onto lighter images..
It's a pandora's box in my view. I'd tend to design an app for the worst case scenario if I were you. Small images, compatible with good view quality, and bullet proof user-notifications when the ISO stack says that something went wrong (timeout, wrong url, no response from server etc...), meaningful transitions from low pic to high pic res, ability to cancel an ongoing request, progress bars etc..
When the user is notified about what's going on, he/she will avoid/understand edge cases situations, and will not blame on the app if something goes wrong.
Now, if you want to address the app performance paradigm, I've started to look into https://newrelic.com/docs/site/apdex (I have no stake into their business, it's provided as an option with my MBaas). Seems there are good things, but I haven't integrated any of their features yet.
good luck !
Related
I live in a building where the laundry machine is a bit far away from my suite. There is only one machine there so only one person can use it at a time. Quite often I take my laundry there just to realize that the machine is in use so I have to go back defeated and try again later. I want to build a doodad that can detect when the machine is in use and broadcast that information throughout the building so that I know that the machine will be available before I go there.
This question is not about how to build the detector. I am planning on using a raspberry pi somehow. This question is about what do I do when I detect that the machine is in use. How do I broadcast that information mainly to myself or potentially to anyone in the building?
I need a cheap solution (< $100). It has to be wireless. The signal has to travel approximately 30 meters in one direction. The broadcast should be readable on any laptop or cell phone (not a requirement but nice to have).
I was considering making an android app using WiFi direct. I'm sure others in the building would be interested in this app and I can use them as peers to extend the range of the broadcast. But I don't like this solution because I know that wifi direct doesn't work with iOS devices. Also this solution will require others to side-load an apk which they might not know how to do.
Please let me know if you can come up with something a bit less reliant on p2p and more platform independent.
For those not in the know, Spaceteam is a very popular and very fun multiplayer game for iOS.
It allows for real time gameplay among multiple devices on an ad-hoc Wifi network - how does it do this?
Are there published libraries describing how to build protocols on top of ad-hoc networking libraries? Is it iOS specific, or would it be possible to build a variety of applications across different platforms?
Quickly, answer before we hit the asteroid!
Specifically which aspect are you interested in? There's nothing particularly special about mobile devices or ad hoc Wi-Fi networks (except in an ad hoc network, not all devices may be able to communicate with each other, so some mesh networking can help but unnecessarily complicates matters for the normal case).
I'll answer the broader question first, because it's more interesting. In my experience, there are a handful of major considerations:
Server/client or peer-to-peer? By this I mean whether there's a "master" deciding the true state of the world and communicating this to all clients. Avara is the only game I know of that is "peer-to-peer" in this sense (peers sent commands to all other peers; this proved bandwidth-heavy for modem users on 6-player games). I am not aware of games using more sophisticated network topologies to communicate game state (e.g. only sending data to one client on each LAN).
What do you do about latency? Avara is the only game I know of which lags everyone locally by the "latency tolerance" in order to get a consistent state of the world, which was terrible if someone was on a modem (turning off compression helped a lot). There are various ways to do "latency compensation" (e.g. in Half-Life/CS), some of which could also work on peer-to-peer games.
Time sync? For client-server games, you at least need to worry about a changing RTT. For peer-to-peer games, I think you also want to agree on timing that minimizes the effective maximum latency.
What if clients disagree about the state of the world? Avara just lets peers decide on their own state of the world (and displays "reality fragmentation detected" if it senses a mismatch, which might happen due to dropped packets or a too-low "latency tolerance").
What if a player leaves? For a P2P game, you might have to agree on a consistent game state (e.g. if the player was disconnected after sending commands to a subset of other peers). For a client-server game, you might have to elect a new master.
And now, after watching the Spaceteam trailer:
I have no idea how it works, since I haven't reverse-engineered the protocol. However, it's pretty simple to make something that works well enough:
Use some sort of P2P discovery to find players (e.g. Bonjour; there should be plenty of docs and samples out there).
Communicate with peers. I've done this with GameKit circa iOS 3/4 (I'm not sure if it still works over Wi-Fi).
Elect a master. This can be as simple as whoever presses "ready" last attempts to be the master. In some edge cases you might have to handle failure.
Let the master decide everything. Spaceteam is not latency-sensitive; Wi-Fi latency tends to be at most a handful of milliseconds, and nobody's really going to notice if one device is slower by 100 ms (as long as the UI responds fast enough).
There is a library made by Spaceteam that does this for Unity games.
https://github.com/hengineer/CaptainsMess
The creator of Spaceteam also wrote an old blog post about Networking in Spaceteam
http://spaceteamadmirals.club/blog/the-spaceteam-networking-post/
There is an iOS only library that will connect nearby devices easily called MultipeerConnectivity https://developer.apple.com/documentation/multipeerconnectivity
If you want something that will work cross-platform I have an example app here: https://github.com/brendaninnis/LocalNetworkingApp, which I explain in great detail here: http://brendaninnis.ca/connect-nearby-devices-part-1.html
Is it possible to get location data out of Google Gears, Google Gelocation API or any other web location API (such as Fire Eagle) in such a format that it appears to other software as a GPS device?
It occured to me reading these answers to my question regarding WiFi location finding, on Super User, that if I could emulate a GPS unit, many of these web services could act as a 'poor-mans' GPS to otherwise less useful software that requires it.
Is GPSD an option?
Preferably OSX & Python, but I would be interested in any implementation.
There is a very similar thread on a Python mailinglist that mentions Windows virtual COM ports and discusses Unix's pseudo-tty capabilities. If the app(s) you want to use let you type in a specific tty device file, this may be the easiest route. (Short of asking the authors to provide a plugin API for what you're trying to do, or buying yourself a $20 bluetooth GPS mouse.)
Are you using OS X?
There is a project macosxvirtualserialport on Google code that provides a graphical wrapper around some of the features of a utility called socat. I'd recommend taking a look at socat if you see potential in the pseudo-tty route. I believe you could use socat to link a pipe from a Python program to a pseudo-tty.
Most native Mac apps will be querying IOServiceMatching for a device with kIOSerialBSDRS232Type, and I doubt that a pseudo-tty will show up as an IOKit service.
In this case, unless you can find a project that has already implemented such a thing, you will need to implement a driver as described in this How to create virtual COM port thread. If you're going to the trouble of create a device driver, you would want to base it on IOKit because of that likely IOServiceMatching query. You can find the Apple16X50Serial project mentioned in that post at the top of Apple's open source code list (go to the main page and pick an older OS release if you want to target something pre-10.6).
If your app is most useful with realtime data (e.g. the RouteBuddy app mentioned in the Python mailinglist thread can log current positions) then you will want to fetch updates from your web sources (hopefully they support long-polling) and convert them to basic NMEA RMC sentences. You do not want to do this from inside your driver code. Instead, divide your work up into kernel-land and user-land pieces that can communicate, and put as little of the code as possible into the kernel part.
If you want to let apps both read and write to these web services, your best bet would probably be to simulate a Garmin device. Garmin has more-or-less documented their protocol in the IntfSpec.pdf file included with their Device Interface SDK. Again, you'd want to split as much as you could into user-space code.
I was unable to find a project or utility that implements the kernel side of an IOKit-based virtual serial interface, but I'd be surprised if there wasn't one hiding somewhere out there. Unfortunately, most of the answers I found to that question were like this, with the developer being told to get busy writing a kext.
I'm not exactly sure how to accomplish what you're asking, but I may be able to lend some insight as to how you might begin to get it done. So here goes:
A GPS device shows up to most systems as nothing more than a serial device -- a.k.a. a COM port if you're dealing with Windows, /dev/ttySx if you're in *nix. By definition, a serial port's specific duty is to stream data across a bus, one block at a time. So, it would then follow logically that if you want to emulate the presence of a GPS device, you should gather the data you're consuming and put it into a stream that somehow acts like an active serial port.
There are, however, some complications you might want to consider:
Most GPS devices don't just send out location data; there's also information on satellite locations, fix quality, bearing, and so on. Then again, nobody's made any rules saying you have to make all that data available. There's probably more to this, but I'll admit that I need to do more research in this area myself.
I'm not sure how fast you can receive data when dealing with Google Latitude, etc., but any delays in receiving would definitely result in visible pauses in your "serial port"'s data stream. Again, this may not be as big a complication as it seems, because GPS devices are known to "burst" data across the bus anyway, but I'd definitely keep an eye on that. You want to make sure there's always a surplus of data coming across, not a shortage.
Along the way you'll also have to transform the coordinates you receive into valid GPS sentences, as well. You can find specifications for those, but I would definitely make friends with the NMEA standard -- even though it is a flawed standard, it's the one everyone seems to agree on anyway.
Hope this helped you, at least a little bit. Are there anymore details specific to your problem that you think could be useful in answering this question?
Take a look to Franson GPS Gate which allows you to connect to Google Earth among other things (like simulating GPS and so on). Is windows only though but I think you could get some useful ideas from it.
I haven't looked into it very much, but have you considered using Skyhook's SDK? It might provide you with some of what you are looking for. It's available for every major desktop and mobile OS.
What sort of application can be considered to be the really business winner for automotive telematics applications related to image processing/computer vision ?
here are the criteria :
1. Innovative
2. Social
3. Fun.
Have you read the articles from the DARPA grand challenge winners?
DARPA site
Google Scholar
I believe the "DARPA Grand Challenge" style of automation meets your .1 requirement as there are plenty of innovation on that front.
But I still think that we are a good decade away from a fully autonomous vehicle, even though the technology is almost there. The main reason is that people are still very afraid of relenting control to the computer, even though it might be the safest choice.
The transition will be slow. More and more models will bring small chunks of automation, such as smarter cruise control systems (that's a big winner right now), autonomous parking (in the market for a while now) and anti collision systems.
Which brings us to your .2 and .3
The above mentioned systems are not fun, they are necessary [for increased safety]. Nowadays, Social Media and Fun don't really mix with driving because they distract the driver from its main task. In the future, when you're on the freeway in auto-pilot mode, you will be able to open your laptop and be free to do whatever you want, since computers will be always connected to the internet. So I don't believe the car itself needs to provide you that aspect of entertainment.
What I do believe it's a killer functionality for cars is the enhancement of intelligent comfort systems integrated with biometrics. Nowadays, cars already have things like personal keys that will make it adjust things like seat height and etc according to your preferences, but it would be much nicer if it could automatically identify who is the driver by some biometric feature (iris, etc) and adjust multiple parameters automatically. That's the end of the key. I'm not talking about seat and pedals adjustment, but transmission style (husband likes a more aggressive transmission), performance limiters (daughter cannot exceed 90% of posted limit... the car knows what the limit is according to where it is).
In my opinion, if you implement biometric recognition + autonomous navigation, the possibilities are endless.
Although none of the applications here use computer vision, they are probably the best once out there yet. They have received quite a bit of media hype.
Where would you recommend that I find a company to develop or buy a CD/DVD loading arm similar to: http://www.dextimus.com/
Preferably programmable via USB but if I only can get one with a serial interface that would be fine. Drivers dont matter - I can interface directly with the unit as my situation is very unique.
If you have some experience with electronics, you can give it a shot and build it yourself, like this or this.
I should add that the schematics and the source code are included, and in more details in the first project.
I suppose I might just shorten this by giving a list of resources first:
http://www.embedinc.com/ I trust this company to do good work. Expensive (actually, they are reasonably priced in the design community, but would be considered expensive by most hobbyists and individuals). Not great at people skills, but very very very good at what they do.
You should check out the various microcontroller communities and forums for hobbyists and professionals that can do this. Search for microchip, atmel, msp430, arm, powerpc, etc.
Sparkfun is a supplier to the electronics community - they have great forums where you can post your request, and you'll find people who might do it for fun with only the cost of materials. Might take longer, might not be as 'professional' or well packaged and delivered, but it might be your best low cost option.
There are many electronic design companies that could do this (for instance, I can do this sort of thing).
But there are many questions you haven't answered (and may not have researched) that could prevent success:
Is this patented?
What CD loading/unloading methods are not patented, are out of patent, or otherwise available?
What is your design goal - a one off just for you, or a device that can be built in the hundreds for industrial use, or a device meant for general office workers/consumers that is built in the millions?
Do you realize that this design qould surely cost mroe than simply buying one, if one is all you need?
As an example, assuming you don't need the nice enclosure and don't mind a 'prototype' look, just the mechanicals, electronics, and firmware design (no software on the PC) would likely be 100-250 billable hours for a design firm. At a cheap $90/hr, that's $9k to nearly $25k for one prototype. Add PC software and the nice enclosure, etc and you'll double that.
If you can find a local 'Make' group (techshop, GoTech, or similar) then you might be able to find a hobbyist that is willing to play with this idea for the cost of materials.
But if you define what your goal is, and give us an idea of your resources you may find a better answer.
-Adam
You can create a very nice simple solution using radio control servos. They come in many sizes, but even the small ones have enough torque to move a big arm to move a cd.
The real bonus with servos is that they normally have 180 degrees of rotation and internally have a variable resistor (rheostat) for positioning feedback. Positioning accuracy is normally within 1 degree of rotation which should be fine for a cd loader.
For picking up the CDs, nothing will beat a vacuum. I recommend a small battery powered vacuum cleaner. Funnel the suction into a 1/4 inch pipe. At the other end of the pipe a one inch diameter cup should provide more than enough lift from the small amount of suction.
As for the pile of blank CDs to be burnt, I would advise in moving the pile up rather than an arm down to it. probably having the top blank cd about 1/4 inch higher than the cd tray - By doing this, the arm only needs to rotate in one axis and the vacuum should be enough to suck the cd back out of the tray.
Now, for the electronics. For the servo control I suggest an rs232 serial servo controller. I've used the one from http://www.basicx.com/Products/servo/servo8t.htm as it also gives back torque information from the current draw.
For the low sample rate digital i/o, i suggest (for windows) inpout32.dll which is a dll to give you direct access to the bits of a parallel port. This will allow you to turn on the vacuum at the correct time and possibly sense when cd's have run out. Note that a parallel port can sink more current than it sources so for outputs you should connect to the 5v power line and set the output pin to 0 to turn on the output and 1 to turn it off.
The other nice option, which is very, very simple to interface and very cheap is to get hold of a picaxe from http://www.rev-ed.co.uk/picaxe/. These use a very simple programming language (a BASIC spin off) allowing you to read serial data in and control the servos and digital I/O on one chip. Last time I used one, the language was a bit simple - if statements had to jumped labels, else didn't exist.
If you do use a microcontroller and servos, it is best to use a dual voltage power supply as servos are noisy and can cause the microcontrollers to reset.
As for switching loads such as the vacuum on, you'll need to use a mosfet or (if money is no object) the simpler option, a solid state relay.
All digital inputs you use on the microcontroller should be pulled either to +V or ground with say a 5k resistor so they never float.
I cannot stress how simple and cheap the picaxes are. They have a built in interpreter so although code space is minimal on the small 8 pin units, they are programmable via a simple serial lead.
Good luck. Once you get into automation control, you'll never be able to stop. I'm in the middle of building a 3 axis CNC router so I can cut parts for other projects (I tell my girlfriend it's so she can cut out xmas decorations!).
You might want to contact Aaron Shephard about his Florian project.
I've found that a really easy board to control stepper motors or sorvos are produced by phidgets - the API is incredibly easy, and available for a vast array of platforms.