Wikipedia:Reference desk/Archives/Computing/2014 April 19

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April 19

Another Heartbleed question

From what I understand, the designer(s) wanted a way for servers to check if the other party is alive. The most obvious implementation would be:

Server A - Are you alive?

Server B - Yes, I heard you

Yet the conversation seems to be:

Server A - Just checking if you didn't die yet. Can you say "Chicken"?

Server B - Chicken

The RFC says that it was designed to overcome the following limitation: "The only mechanism available at the DTLS layer to figure out if a peer is still alive is a costly renegotiation, particularly when the application uses unidirectional traffic. Furthermore, DTLS needs to perform path MTU (PMTU) discovery but has no specific message type to realize it without affecting the transfer of user messages."

Just "Yes, I'm alive" seems to be enough for this purpose. Why did they decide to ask the other side to echo a string in the first place? Are there other protocols that have implemented a heartbeat message that uses a "challenge-response" method like this, possibly making sure it's not a faulty router replying? Especially when the "challenge" is to reply with the exact same string instead of, for instance, a checksum of that string? Joepnl (talk) 00:11, 19 April 2014 (UTC)

DTLS is Datagram TLS, and people have argued that arbitrary payloads could have uses there (see sagemode's post in that thread especially). It was also added to the far more widely used TLS-without-the-D because, hey, why not. -- BenRG (talk) 01:10, 19 April 2014 (UTC)

This looks like an attempt to salt (cryptography) the correct reply, to make it harder for a Man in the Middle to fake valid replies. - ¡Ouch! (^{hurt me} / _{more pain}) 06:00, 24 April 2014 (UTC)

Server A – If you're still alive, say "Penis".

Server B – Error: Passphrase too short.

stop-frame animation and morphing

My 17-year-old daughter wants to make a video using stop-frame animation of Lego people. She is wondering if it would be faster to shoot fewer frames and use morphing software to go from one frame to the next.

Second, I think either approach will be very time-consuming. How long do you think it would take per second of video produced? Bubba73 ^{You talkin' to me?} 03:02, 19 April 2014 (UTC)

Whether morphing is quicker would depend on the speed of the computer versus the speed for each change in position. If only one figure is moving, that ought to be quick to adjust, versus say, having an entire football field move. And you can only do so much morphing, perhaps every other frame, or it will start to look bad. You also have to put some thought into which positions you show when doing morphing. While walking, for example, you would want to capture the right foot all the way forward, and the left foot all the way forward, because morphing will never move it farther than what you have captured. If you just capture a figure standing at one position, then standing at another, the morphed version would have him slide from one position to the other, not walk.

How long it takes will also depend on the frame rate. At 10 frames per second it would look "jumpy" but might only take 10 minutes to film a second, if she can adjust the scene in a minute. StuRat (talk) 03:11, 19 April 2014 (UTC)

I was telling her that it might take an hour to produce 1 second, all things considered. Bubba73 ^{You talkin' to me?} 04:08, 19 April 2014 (UTC)

I'm not exactly Pixar here, but I have a quad-core i7 and two quad-core i5s. I saw morphing done at Comdex in 1994, when the Pentium was new. Bubba73 ^{You talkin' to me?} 04:33, 19 April 2014 (UTC)

Also, one advantage of morphing is that you don't need to be there while the computer works. If you can set up a job to morph between all your captured frames overnight, it really doesn't matter if it takes all night. (If you don't need the computer for other things, you could even run morphing software 24/7.)

Unfortunately, it may be time consuming to define which point in one frame corresponds to which point in the new frame. It would be nice if the morphing software itself could figure out that his left elbow in one frame goes with his left elbow in the next frame, but I'm not sure if it can do that yet, reliably (especially if the arm goes straight in one frame and the elbow "disappears"). I would expect that each joint would need to be so defined. StuRat (talk) 10:40, 19 April 2014 (UTC)

She wants to do a scene from Of Mice and Men that way for extra credit in literature class (which she doesn't really need). I told her that could take 100 hours or more. She doesn't believe me. Bubba73 ^{You talkin' to me?} 18:51, 19 April 2014 (UTC)

I always estimate at least one minute of video editing for each second of final film for normal film projects. If you include shooting, things start going up from there. If you add visual effects - even stop-motion - things get incredibly time-consuming. You can see why professional stop-motion studios - like Wallace and Gromit, by Aardman Animations, estimatedly required about 10 to 24 hours per each second of stop-motion footage - as much as one hour per frame. Naturally, your project complexity is lower than a major motion-picture, but you should still not under-estimate the effort, the time, and particularly pay attention to the workload that is non-parallelizable. Nimur (talk) 19:34, 19 April 2014 (UTC)

For what she wants to do I'm thinking about 1 minute per frame. Bubba73 ^{You talkin' to me?} 20:13, 19 April 2014 (UTC)

Might I suggest the final scene, where George tells Lennie to think of rabbits, then shoots him ? Very little motion takes place, yet it's quite dramatic, so could give you a lot of bang for the buck. You might need to check if such portrayals of violence are OK with the school, though. I suggest showing them from behind, so you wouldn't see their mouths moving, to reduce the workload dramatically. The sounds of barking dogs from the search party would add to the effect. She could show George slowly raising the gun, and could cut to black, just hearing the sound of the gunshot, at the end. StuRat (talk) 04:36, 20 April 2014 (UTC)

she has a scene in mind, and it might be that one, since she demonstrated a arm moving down. Bubba73 ^{You talkin' to me?} 04:39, 20 April 2014 (UTC)

OK, but you might want to check with her, as she may have a far more ambitious scene (or treatment of that scene) in mind, and might then get discouraged when she sees all the work that's required in order to do it justice. She could also have him raise and lower the gun a couple times, as if he can't quite force himself to do it. This would have the practical benefit of reusing the same frames, so she'd get more motion per frame. StuRat (talk) 07:29, 20 April 2014 (UTC)

If you are looking for software tools, I suggest "key frame" or "key framing" is a better description that "morphing", e.g. Key_frame#As_applied_to_motion. As others have discussed above, it's not necessarily clear which way will be faster, there are too many variables and decisions. But, if you use some software to fill in between the key frames, then she'll learn another cool technique at the same time :) SemanticMantis (talk) 16:13, 21 April 2014 (UTC)

Here are a few threads and tutorials I've found dealing with your specific issue [1] [2]. There are reputedly iOS apps that "automagically" do interpolation between frames for you. That might be the easiest bet, if you have an appropriate iProduct and budget. SemanticMantis (talk) 16:25, 21 April 2014 (UTC)

I've also heard it called "tweening" at least in the case of Flash animation. StuRat (talk) 15:42, 22 April 2014 (UTC)

ASCII code of ″ ?

For instance, the article Eiffel Tower gives the tower's coordinates, aka 48°51′29.6″N 2°17′40.2″ or (in the 2nd page, when you've clicked the coordinates) 48° 51′ 29.6″ N, 2° 17′ 40.2″ E . My question is : what is the ASCII code and the Excel code of this character: ″ = a kind of quotation mark (the one I've got on my PC is " which is not the same).

In Excel, my problem is: when I use the function =CODE(″) I get 63 as the answer but when I reverse it, =CAR(63) gives ? and not ″ . Thanks in advance. 178.199.181.217 (talk) 16:07, 19 April 2014 (UTC)

I believe the double quote is as close as you will get in 7-bit ASCII codes. Some 8-bit ASCII code pages use character 211 as the closing double quote (with a different character for the opening double quote), so that might work.

I assume you meant CHAR(63), and I guess the problem is that it's using the returned character as a string terminator, which confuses things. Are you forming a string like this:

PRINT CHAR(63) 

? If so, try wrapping single quotes around it, like this:

PRINT ' // CHAR(63) // '

or maybe this:

PRINT "'" // CHAR(63) // "'" 

(Fortran syntax, but hopefully similar to Excel). To specify a different character, you'd likely need to go to Unicode instead of ASCII. Does Excel support Unicode ? StuRat (talk) 16:20, 19 April 2014 (UTC)

The characters referenced are the prime (′) and double prime (″) represented as Unicode values 2032 and 2033 (hex) or 8242 and 8243 (decimal). There is no direct equivalents in the 128 character ASCII character set, so the single and double quotes are commonly used as substitutes. In Excel 2013, these characters can be inserted in an expression as =UNICHAR(8242) or =UNICHAR(8243). The codes themselves can be extracted as =UNICODE("′") or =UNICODE("″"). (The latter string literal is a double quote, double prime, double quote sequence.) Earlier versions of Excel do not support the UNICHAR() and UNICODE() functions, but you can still paste unicode characters into a quoted string. The CHAR() function only supports 8-bit characters. Any other characters are first converted to the question mark, which is why =CODE("″") yields a 63. -- Tom N talk/contrib 18:12, 19 April 2014 (UTC)

There are Wikipedia articles linked from most printable Unicode punctiation: in this case, the info you want is at ″ which redirects to prime (symbol). 70.36.142.114 (talk) 04:50, 20 April 2014 (UTC)

Thanks for all your comments. ALT-8243 in Word writes the searched "double prime" - great ! - but ALT-8243 does not work here with the Wikipedia editor and that does not work in Excel either. The function UNICAR is not available in my Excel 2007 but seems to come with Excel 2013. 178.192.217.219 (talk) 15:10, 24 April 2014 (UTC)

export list of people categorized by some criteria

Hi, In the previous century Michel Gauquelin created statistics relating people occupation and their zodiac sign. He did this manually, without a computer and Internet. Now we have a wiki and all these data are here. So I'm looking for a way (bot/script) that can export the list of people categorized by their occupation or other criteria + their birth date. I will import this in excel which will calculate the zodiac sign and will draw a nice graphs. Any idea will be good for me. Thanks in advance!

Nikolay — Preceding unsigned comment added by Jamezx (talk • contribs) 17:00, 19 April 2014 (UTC)

I can't directly answer your question but, rather than reinvent the wheel, you should know there are lots of astrological databases out there already (for example this one, and an astrological forum might be able to recommend one suited to your requirements.--Shantavira|^{feed me} 08:48, 20 April 2014 (UTC)

You should also know that a birth date alone gives a less than accurate position of the Sun (for it's the Sun, not the Moon or any of the planets, that people talk about when they say "zodiac sign". The Sun is indeed important, but it's by no means the only factor). On a certain day every month, the Sun moves from one sign to the next, and without knowing the precise time and location of a child's birth, it's not generally possible to say which sign the Sun was in at the moment of birth. People often fudge this by talking about cusps, and say a child born on the changeover day (or even 1 or 2 days either side) has characteristics of both signs. That's a little like saying the number 1 operates much like the number 2 because they're close together. Very scientific, not. -- Jack of Oz ^{[pleasantries]} 00:22, 25 April 2014 (UTC)

Mutual friend in facebook

When I log in to facebook and type fist letter of the person to whom i have sent friend request and is yet to accept the rquest appears his picture and name appears below search box and also " 1 mutual friend " though i have none such presently.What does this mean.When i type an alphabet or a few letters in search box a list around 4 peoples picture appears in list form .How is people you may know list generated. Are they at random ?117.194.242.150 (talk) 17:59, 19 April 2014 (UTC)

Part of it seems to be location. Apparently they assume everyone in the same postal code must know each other. As far as "mutual friend" goes, I assume that means that both you and this guy have a common "friend". StuRat (talk) 18:42, 19 April 2014 (UTC)

No I have no mutual friends.117.194.242.204 (talk) 03:49, 20 April 2014 (UTC)

The suggestions I get for "you may know" are friends of friends (that is, they have a mutual friend with me). - Purplewowies (talk) 21:38, 19 April 2014 (UTC)

How to really remove Savings Bull

A friend of mine got the malware Savings Bull installed on her computer either from installing Skype or visiting a travel website. I have uninstalled it for her and cleaned it from her browsers and uninstalled every program that shows as installed on her computer this year, but it keeps coming back. I followed the online instructions that said to use a command prompt to look for associated files, but was not able to identify any. Does anyone have advice where to look at this point? I rand these instructions, but found nothing I could figure out should be removed at the regedit step: http://blog.qisupport.com/remove-savings-bull-filter-remove-pesky-adware/ Thanks. μηδείς (talk) 20:40, 19 April 2014 (UTC)

One thing to watch out for is Chrome auto-syncing settings. My wife accidentally installed something she shouldn't have a few days ago, and cleaned it up right away, but some of the less dangerous bits like the home page and search provider change got synced to her account. After logging back in, the settings came back, including on her android tablet. It was easy enough to clean up, but at first it made it look like the infection had come back on her PC even though it was only the browser settings.

What OS is she running? If she has Windows 8, then a system reset is simple and will almost certainly clear it up, but she'll have to reinstall her programs. All of her files will be safe. Katie R (talk) 12:33, 21 April 2014 (UTC)

• It's Windows Vista. She doesn't use anything other than her browser and a printer. She's an 85 y/o travel agent so her needs are simple. The problem seems to have happened when her d-in-law installed skype. She always does the automatic install and imports a load of crap. Can I do a system reset for her without any risks? μηδείς (talk) 17:58, 21 April 2014 (UTC)

System reset is a Windows 8 feature that makes restoring the OS to its original state without hurting files very simple. Vista doesn't have something like that, but the system probably has a recovery partition that can be used to reinstall the whole system. There is usually some way to tell the system to boot to it at startup, but it varies from system to system. I would just back up any files she needs to a flash drive and try to figure out how to reinstall. The malware can probably be removed some other way, but it probably isn't worth the time to figure it out, especially since it doesn't sound like it will take much to get the fresh system working how she needs it. Just make sure to run Windows Update once you're done. Katie R (talk) 12:23, 22 April 2014 (UTC)

Hmm. My friend does still have all her original restoral disks. I am leary of reinstalling everything, but I will present it ot her as a possibility. μηδείς (talk) 21:34, 23 April 2014 (UTC)

Garage door switch (update and thanks)

Resolved

See Wikipedia:Reference_desk/Archives/Computing/2014_April_8#Name_that_electric_switch. I got the device to solve this problem, as you guys suggested, and it works great ! I've now disconnected the extension cord I had coming from the garage door light to power all my exterior lights, and I'm powering them from mains power, instead, but still triggered off the power pulled down by the garage door opener and lights (the garage lights are enough to trigger it). Special thanks to Vespine, who came up with the winning suggestion. StuRat (talk) 20:31, 19 April 2014 (UTC)

That's great! It's rare an answer on the help desk actually has a real world application :) Happy I could help.Vespine (talk) 22:57, 21 April 2014 (UTC)

Maybe more common here than on other desks. Thanks again ! StuRat (talk) 15:43, 22 April 2014 (UTC)

Topo maps for apps

If I wanted to make a smartphone app that required topographic data, would there be somewhere that I could get that data for free? I'm basically thinking of lat/long and elevation of various peaks. Thanks, Dismas|^(talk) 23:21, 19 April 2014 (UTC)

Data from Shuttle RADAR Topography Mission is available at no cost. Nimur (talk) 16:41, 20 April 2014 (UTC)

There is also OpenStreetMap, if it covers the area you are interested in. Looie496 (talk) 17:06, 20 April 2014 (UTC)

Thank you! Dismas|^(talk) 10:42, 21 April 2014 (UTC)