Wikipedia:Reference desk/Archives/Computing/2009 November 7

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November 7

Collapsing JPGs into a video

Resolved

Hello! I have a lot of JPG files of screenshots that I want to compress into a single video file. The screenshot program saves the screen image about every second to a JPEG (not ideal, I know). I would like to create the video file by specifying about a .2 second delay in-between images to get an animation. Is there any free and open source software out there that will let me do this? And is there a video format that will take up less space by eliminating all the redundant information in the jpegs (since the screen hardly changes every second)? Thank you!--el Aprel (^facta-_facienda) 05:19, 7 November 2009 (UTC)

If you have Linux, you can do something like [1] (or you can get mplayer on Windows, dunno how easy that is though). --antilived^{T | C | G} 05:48, 7 November 2009 (UTC)

Thanks, antilived. Actually, after I posted this question, I realized Windows movie maker does this fairly well.--el Aprel (^facta-_facienda) 05:58, 7 November 2009 (UTC)

This often seems like so much 'black-art' - but understanding what's going on 'under the hood' is very instructive in this case:

Most video codecs compress data by comparing two consecutive frames and storing only the differences between the two. For still images - there are no differences. Hence, at first sight, it shouldn't make MUCH difference to the final size of the file whether you record at one frame every two seconds or 60 frames a second because the differences will be zero for almost all of the frames.

However, there is a little 'gotcha' which is what's going to dominate the size of your resulting files. Most formats store things called 'i-frames' at some interval. i-frames are simple, complete video frames with no difference coding. By default, they store them perhaps one per second or so - but with decent software, you can control this interval. They do this to allow you to jump in at the middle of the video without having to start at the first frame and add up all of the differences up to that point. So the video file contains a series of i-frames (maybe one per second) - each followed by a bunch of 'difference' frames (called: p-frames and b-frames for reasons too complicated to explain here).

So what you need to do is to make sure that you aren't generating i-frames at greater than the update rate of your images and ideally, you'd want to make the i-frame timing come at precisely the update rate of your images so all of your p- and b-frames are empty. If you get that right, it won't matter much what frame rate you pick because each frame will just say "no changes from the previous frame" - which is a minimal amount of information. You can read more about this in Video compression picture types. Good video compression software gives you control of the rate of i-frames - check out (for example) mplayer and mencoder.

SteveBaker (talk) 16:16, 7 November 2009 (UTC)

Thank you very much, SteveBaker! That really clears up a lot of the doubts I had about how to compress out all the old frame data. I will have a look at the software you mention.--el Aprel (^facta-_facienda) 19:37, 7 November 2009 (UTC)

A theoretically better way, which may or may not work in practice, is to use variable-length frames. That is, instead of encoding 10 identical frames in a row at 5 fps, just encode one frame and tell the player to display it for 2 seconds. AVI doesn't support variable-length frames, but Matroska does. Matroska isn't supported by nearly as many players as AVI, and I don't know how many Matroska-producing tools will let you produce variable-length frames, but if you can get it to work you will get a smaller file and playback will be easier on the CPU. -- BenRG (talk) 23:31, 7 November 2009 (UTC)

BSOD

Does Microsoft refer to the Blue Screen of Death by that name? jc iindyysgvxc (my contributions) 09:17, 7 November 2009 (UTC)

[2][3]F (talk) 09:26, 7 November 2009 (UTC)

Looks like it is only the occasional "tech column" and tech support that mentions it as such. Doesn't look like they officially use it in any of their official literature. --Mr.98 (talk) 12:52, 7 November 2009 (UTC)

The official terms are "blue screen", "bug check screen" and "stop screen" according to this page. I doubt you'll find "BSOD" in official Microsoft documentation. "Blue screen" by itself is somewhat ambiguous because NT uses the same blue screen for startup messages, though as of XP it doesn't look much like the bug-check blue screen any more. -- BenRG (talk) 13:28, 7 November 2009 (UTC)

Javascript and windows handles?

This is a very strange question, but can javascript be written to retrieve the "Handle" to a users desktop? (mine is currently "65842" in decimal).

Also can it detect the Operating system and only output the result to the web page if the user has Vista Premium or Vista Ultimate? Thanks!

137.81.112.176 (talk) 10:28, 7 November 2009 (UTC)

Javascript can't manipulate anything outside of the browser scope. That would include the desktop.

It can, however, detect the OS — here is some code. However I'm not sure it can detect the difference between Premium or Ultimate specifically if you want that... looking at my own server logs, all Vistas look pretty similar, but there are a lot of numbers involved (e.g. here is one Vista machine: MSIE 7.0; Windows NT 6.0; WOW64; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.5.21022; .NET CLR 3.5.30729; .NET CLR 3.0.30618), so maybe one of them indicates Premium v. Ultimate. Hmm. Note that crafting your page to be compatible with only one browser is pretty bad design, and if it is because of incompatibilities, indicates fundamental problems in the coding (reliance on proprietary functions, etc.). Once you've detected Vista (look for that "Windows NT 6.0" string), you could easily have an operator at the top that either redirected the page somewhere else or refused to output the rest of the page. --Mr.98 (talk) 12:49, 7 November 2009 (UTC)

Okay let me fill you in a little. I am doing something that can only be done in Vista premium or MAYBE ultimate, it is simply that what i am getting a user to do CANT be done at all in any other OS, so its not really some mainstream website for all to see. Also, if JS cant detect the desktop handle due to scope, is there anything i can attach to the site to do so besides making the user download something? :) —Preceding unsigned comment added by 137.81.112.176 (talk) 13:12, 7 November 2009 (UTC)

As for Vista, well, OK, I guess, though I do wonder what it is you are trying to do that is apparently dependent on only one or two flavors of a single OS. As for accessing the filesystem, you can't do it with Javascript (with the one exception being that you can have users upload files through form submission, but that's it). There are other options—like Java applets—that can do more than that (with the approval of the user). Javascript is inherently limited to browser scope, though, for security purposes (imagine the mayhem if every page out there could access your hard drive contents). --Mr.98 (talk) 13:37, 7 November 2009 (UTC)

I think my anser, then, lies in making an "AutoIt v3" script, which does handles and could be downloaded by a user in exe format. thanks!

137.81.112.176 (talk) 01:12, 8 November 2009 (UTC)

Resolved

Game For ZX Spectrum

Does anyone remember the name of a game for the ZX Spectrum where the player takes command of a robot shaped like a ball with three legs, walking around a map of a town and shooting bouncing bombs at flies? I think it begins with 'A'. Cheers! --KageTora - SPQW - (影虎) (talk) 12:56, 7 November 2009 (UTC)

If you don't mind the robot having four legs, there's Amaurote. 88.112.58.122 (talk) 14:20, 7 November 2009 (UTC)

Excellent! That's the one! --KageTora - SPQW - (影虎) (talk) 14:45, 7 November 2009 (UTC)

Windows 7

Just like to say thanks to all here for the recent help with my Windows 7 questions. I've installed it and it's working great, so much better than Vista (so far anyway... hoping there won't be any big problems >_>) —Preceding unsigned comment added by 82.43.89.85 (talk) 14:08, 7 November 2009 (UTC)

Glad to hear it. Keep us posted, I'm sure that those of us considering getting Windows 7 would love to hear about any warnings or problems, before we make the plunge. StuRat (talk) 23:58, 7 November 2009 (UTC)

Microwave oven that blows my circuit breaker

It works fine most of the time, but every few months it causes the circuit breaker to pop, sometimes only when the door is opened (which turns on the light). I don't want to toss out the microwave oven because of this, but it is rather annoying to go down in the basement with a flashlight searching for the fusebox. Is there any fix for this ? If nothing else, I suppose a surge protector with a low amperage circuit breaker would work here. Then, every time it pops, I could just reset it right there. Do they sell something that looks like an outlet strip, and has a circuit breaker, but lacks surge protection ? If so, maybe that would be cheaper. StuRat (talk) 14:16, 7 November 2009 (UTC)

It certainly sounds like your microwave is faulty. That makes it potentially dangerous. You need to either replace it or get a professional to fix it. --Tango (talk) 20:23, 7 November 2009 (UTC)

What danger is there other than it overloading the house wiring ? That danger can be addressed simply by adding a power strip with a circuit breaker, right ? StuRat (talk) 23:56, 7 November 2009 (UTC)

What exactly is being triggered though? Is it the circuit breaker or the RCD? --antilived^{T | C | G} 00:03, 8 November 2009 (UTC)

It is a circuit breaker, in the fuse box in the basement. StuRat (talk) 00:06, 8 November 2009 (UTC)

This may indicate a fault with the switches that detect if the door is open. These switches are intended to prevent the oven operating with the door open (and thus irradiating the user). One microwave oven that I owned (a National) was wired such that when you pressed the handle to open the door, that handle activated a switch to disconnect the microwave generator, as well as sending a signal to the electronic controller. But the door also had two independent mechanical switches that would close when the door was opened. One of these switches applied a direct short circuit across the microwave generator, so that if the door was open and the handle had failed to stop the microwave generator, the short circuit would prevent the generator from working - and trip the circuit breaker. I have been told that this is not uncommon practice for such applications. The reason being that it is more reliable to short out the "dangerous" item, which will cause any of several fuse or circuit breakers to blow, than to disconnect the circuit. (Personally, I'm not commenting on whether this is a good idea or not, but my oven certainly was wired that way.) Thus if your circuit breaker keeps tripping, it might indicate a fault in the power supply to the microwave generator. Mitch Ames (talk) 00:54, 8 November 2009 (UTC)

Here's some links describing this concept, found by a Google search for microwave oven door switch short circuit: Description with circuit diagram, Patent (the first of several found by the search). Mitch Ames (talk) 01:03, 8 November 2009 (UTC)

Thanks, that's quite informative. StuRat (talk) 15:50, 8 November 2009 (UTC)

Microwaves can be dangerous, so you should really replace it. Here's a video of a science program where the presenter "builds a microwave death ray to prove the existence of invisible and untapped energy". --h2g2bob (talk) 01:59, 8 November 2009 (UTC)

But my microwave oven is dangerous how, exactly ? Is it going to generate microwaves with the door open ? Is it going to catch fire ? What's the safety concern ? StuRat (talk) 15:45, 8 November 2009 (UTC)

The fire part is what you need to be worried about. Tan | 39 15:48, 8 November 2009 (UTC)

But if the circuit breaker pops whenever there's a short circuit, won't that prevent a fire ? StuRat (talk) 15:50, 8 November 2009 (UTC)

You need to be worried about why the breaker is tripping. You have one of three problems: an overloaded circuit, a short circuit, or a ground fault. If I had to guess, you have a short circuit caused by some loose or miswired circuits with the microwave door. So now, in effect, you are trusting your circuit breaker to kill that short - and possibly prevent a fire. If I were you, I wouldn't trust my kitchen and house to a circuit breaker; I'd have it fixed or replace the entire unit. Tan | 39 16:01, 8 November 2009 (UTC)

Yes, it seems to be a somewhat intentional short circuit, according to the info Mitch Ames provided above. StuRat (talk) 16:36, 8 November 2009 (UTC)

TCP/IP not enabled

Whenever I try to repair the connection labelled as 1394 connection under "LAN or high speed internet" in Network Connections, I get the error message "Windows could not finish repairing becuase TCP/IP is not enabled" But when I got to that connections properties, I can see that it is enabled. Is there any way to fix this problem? (I use Windows XP.)Thanks in advance. 117.194.224.97 (talk) 17:36, 7 November 2009 (UTC)

IEEE 1394 is more commonly associated with connections to video cameras. It is unusual to use it as an interface for TCP/IP networking (though it can be done). Astronaut (talk) 00:29, 8 November 2009 (UTC)

Game for Commodore 64?

Relating to the question about a game for the ZX Spectrum above, I have to ask this question here. I played a Commodore 64 game at my cousin's place in the early 1980s. The only recollection I have of it is that it was made in the early 1980s, it came on a cassette tape, it was a platformer-style arcade game, and at some point it had a merry-go-round or something. It was not a game for infants but instead a standard, full-blown game for schoolchildren and teenagers. I think it may have had something to do with Pac-Man but I don't trust this memory, I might have it confused with some other game. This description isn't of much help, but my memory is very vague, because I only ever played it once, and this was over two decades ago. My cousin wouldn't remember it if I asked him, that's for sure. JIP | Talk 21:41, 7 November 2009 (UTC)

There are websites that are about C64 games, including some that have been re-made to run on Windows, so I suggest Googling for something like "commodore 64 games" and see if any of the sites that come up mention your game. 78.147.8.170 (talk) 13:45, 8 November 2009 (UTC)

How to help a nincompoop?

An acquaintance sent me mail to ask if I could help him with a computer problem, and I said sure, because it was a very simple problem. But it turned into a nightmare; he never does what I tell him, and comes up with the weirdest alternatives instead. He has this half knowledge that is dangerous enough to wreak havoc, but he has problems understanding even what a link is. My dilemma is: I want to get out of this, because even if I help him this time, I'm sure he'll come up with more such requests later. But I do not want to offend him, and I can not just turn my back on him because I see him on other occasions. How to get out of this? I thought of pointing him here, but that probably wouldn't be fair to the rest of you. Compu732 (talk) 22:06, 7 November 2009 (UTC)

I have one of these - you may want to get one! --Tango (talk) 22:14, 7 November 2009 (UTC)

That's a good idea - it's certainly a notch more polite than "Go away or I'll replace you with a shell script". But the thing is, I do enjoy helping other people - just not this particular one. Compu732 (talk) 22:22, 7 November 2009 (UTC)

That's a very good idea. Whenever I talk to strangers and mention that I work as a computer programmer, they immediately ask if I can fix their Internet connection or peripherals for them. Internet connections and peripherals aren't even my speciality - my education and work experience is very near to 100% software. I've only ever had to deal with hardware when upgrading my own computer. JIP | Talk 19:10, 8 November 2009 (UTC)

Shrug and say "I really don't know, maybe you need to ask someone else". —Preceding unsigned comment added by 82.43.89.85 (talk) 22:26, 7 November 2009 (UTC)

I hate the idea of him telling everyone else "he didn't even know that". But you may be right, it's usually a good idea to give up one's foolish pride. Compu732 (talk) 22:30, 7 November 2009 (UTC)

I second the idea of claiming to be at the end of your own knowledge, or your own abilities, and recommend he take it to, say, BestBuy or whatever. It's not actually any skin off of your back, and it'll save you time. The sooner he decides to start going elsewhere for computer help, the better you'll be. --Mr.98 (talk) 03:39, 8 November 2009 (UTC)

Tell him that you have to use VNC to help him in the future for the sake of precision and that diagnosing and fixing problems via a game of Telephone is inefficient and actually dangerous. Tempshill (talk) 07:00, 8 November 2009 (UTC)

Why not just politely tell him what you have told us. Do not call him a nincompoop though. 78.147.8.170 (talk) 13:48, 8 November 2009 (UTC)

So what would you call him? Compu732 (talk) 05:58, 9 November 2009 (UTC)

http://www.xkcd.com/627/ SteveBaker (talk) 21:48, 8 November 2009 (UTC)

That's hilarious! Even my gf loved it. Compu732 (talk) 05:58, 9 November 2009 (UTC)