Wikipedia:Reference desk/Archives/Computing/2009 November 2

= November 2 =

blog-style website
I'd like to start a blog-style website, but I'm not sure which host would be right for what I have in mind. Specifically, I'd like a site that allows for very detailed categorizations of each post (sub-categories, easily make new categories, handle large quantities of categories, that kind of stuff). A setup that would allow me to automatically queue up multiple days of uploads would be nice. Adding pictures would be a bonus, but not a deal-breaker; this could be a completely text-only kind of thing. There seem to be dozens of different sites and it's hard to tell which one would be a good fit for me. Any suggestions? Matt Deres (talk) 02:23, 2 November 2009 (UTC)


 * WordPress can give you queued uploads, easy categories, large quantities of them, but is not so much about hierarchical sub-categories (and I might suggest that you probably don't need them—most sites don't). Can add pictures, etc. All for free on http://wordpress.com/ (you can migrate it to a private domain later if you want) and with loads of community-developed add-ons. Easy to set up. Give it a whirl! Let me suggest that 90% of a blog is just sitting down and writing it. Don't worry about the bells and whistles until you have actually proven to yourself you can stick with it for more than a week. --Mr.98 (talk) 02:47, 2 November 2009 (UTC)


 * Content will not be a problem, I think :). Wordpress was the one I'd been thinking of, though the security problems (as raised on the article space) are a (minor) concern. I could do what I want to do without sub-categories, but it seemed an easy way of of dealing with what I'm planning. If it's not available, somehow I'll struggle on. Matt Deres (talk) 03:11, 2 November 2009 (UTC)


 * If you run it off of the Wordpress servers (e.g. wordpress.com hosting), the software will always be up to date, and the security will not be an active issue. For everything else, the update process is really easy. As for sub-categories... I would search around for a WordPress plug-in that did it. There probably is one. It is a very flexible, adaptable platform. (And on content... no one thinks it will be a problem, but it is usually the limiting factor. It takes a lot of time to write a good blog post, and people go through them pretty quickly... just speaking from experience! It is harder than it looks...) --Mr.98 (talk) 04:02, 2 November 2009 (UTC)


 * Okay, Wordpress it is unless someone pops by with something better in the next few hours. I don't doubt that most blogs fail from lack of content, but I'm not planning an opinion or diary style thing, but something more like the "Strange Maps" and "What Were They Thinking" blog-style sites (both of which run on Wordpress). I've got the first 200+ posts basically done except for some tweaking and organizing, so that will buy me a bit of time before I have to start scratching my head again. ;) Matt Deres (talk) 20:31, 2 November 2009 (UTC)

Xbox 360 backwards compatability
Well, I downloaded the disc that makes my Xbox 360 able to play original Xbox games. However, when I put in my copy of True Crime: Streets of LA (subpar game but the only original Xbox game I have), a message appears (in six languages, mind you) telling me "This is an Xbox game disc. Please put it in your Xbox to start playing." Well, shouldn't have the disc I just installed to my Xbox 360 fixed that problem? 71.213.70.217 (talk) 03:18, 2 November 2009 (UTC)

Note: This was moved from WP:VPM. Killiondude (talk) 03:25, 2 November 2009 (UTC)

Not all games are backwards compatible. Check out the site |where Microsoft lists the backwards compatible games. Your game appears to be on there, but you should check a few things.


 * 1) Do you have the latest backwards compatibility software?
 * 2) Is the game an American copy? Is the Xbox an American Xbox? If the regions don't match, it causes issues.

The other option is to go |here to the 360 compatibility FAQ or go here, |here where your specific issue is addressed. I'd start with the bold link.

Nezzadar  [SPEAK]  05:28, 2 November 2009 (UTC)
 * Wait a minute, there's a disc? I thought it was just like a patch or something you automatically download with every system update. I was under the impression it was sort of an invisible DLC thing. Anakinjmt (talk) 06:30, 2 November 2009 (UTC)
 * If your 360 is on X-Box Live, then it should happen automatically. But a surprisingly large percentage of 360 owners (The Majority!) don't use Live. APL (talk) 16:58, 2 November 2009 (UTC)

Er, you probably don't want to hear this, but confusing game discs with film DVDs was one of the last things my first 360 did before it threw up E74/1 red light. Try swapping round other discs and seeing if the same thing happens. It may just be that disc, but even if it seems that way, it may be the console anyway; my old one only ever got confused by Mass Effect. CaptainVindaloo t c e 14:19, 2 November 2009 (UTC)

Simple C question
I've been at this for over 4 hours and can't figure out why this isn't working. I'm trying to write a simple + - * / ^ calculator that starts at 0 and increments based on user input. When the user presses the character Q or q the calculator quits but it doesn't work (among other things). The  doesn't work, but if I remove the || it works fine, and another interesting thing is that if I make this condition an if statement rather than a while, it works. I can't figure out why this isn't working. Any suggestions? -- penubag  (talk) 06:02, 2 November 2009 (UTC)


 * For your while loop, go back and think it through again (or use Boolean algebra): what would happen if the user inputs "q"? What would this code  return if operator == 'q'? (answer: 1) Is that correct? What if operator == 'Q'? (answer: still 1) --antilivedT 06:24, 2 November 2009 (UTC)
 * Ah, computer code. How I remember the days when I was a computer major trying to learn Java. How you frustrated me so and made me realize that I needed to be a Vulcan to understand your logic. Anakinjmt (talk) 06:32, 2 November 2009 (UTC)


 * It seems correct to me. If the user inputs either a capital or lowercase Q, that program should output the total and quit. -- penubag  (talk) 06:33, 2 November 2009 (UTC)


 * Does it? That code checks if the user input isn't a lowercase q OR if the user input isn't an uppercase Q. Let's try a truth table:
 * {| class="wikitable"

! Input !! A: !='Q' !! B: !='q' !! A OR B !! A AND B
 * 'a' || 1 || 1 || 1 || 1
 * 'q' || 1 || 0 || 1 || 0
 * 'Q' || 0 || 1 || 1 || 0
 * }
 * Right now no matter what the user inputs your while loop condition will always be true because you have it as A || B, when it should be A && B (ie. loop while input isn't 'q' AND input isn't 'Q'). --antilivedT 06:50, 2 November 2009 (UTC)
 * Aghhhh...I see it now. Negative logic hurts my brain. What I was originally thinking was "is operator Q or q". Thanks for the help; I've updated my code above and just have one more bug to fix. -- penubag  (talk) 07:12, 2 November 2009 (UTC)
 * This is exactly what De Morgan's laws stipulate. --antilivedT 10:37, 2 November 2009 (UTC)
 * }
 * Right now no matter what the user inputs your while loop condition will always be true because you have it as A || B, when it should be A && B (ie. loop while input isn't 'q' AND input isn't 'Q'). --antilivedT 06:50, 2 November 2009 (UTC)
 * Aghhhh...I see it now. Negative logic hurts my brain. What I was originally thinking was "is operator Q or q". Thanks for the help; I've updated my code above and just have one more bug to fix. -- penubag  (talk) 07:12, 2 November 2009 (UTC)
 * This is exactly what De Morgan's laws stipulate. --antilivedT 10:37, 2 November 2009 (UTC)


 * It's good for you to be getting practice with logic now, but in production code you might just say "while (tolower(operator) != 'q') ..." or similar. Also, you should indent each block so you can see the logical structure more easily.  --Sean 12:49, 2 November 2009 (UTC)
 * Separately, and opinions vary, but I find the following structure to be clearer:


 * This changes the structure from your:

input test loop: test input output
 * to:

loop: input test output
 * and since you don't repeat yourself on the input operation, you only have to change it in one place if it changes. --Sean 13:02, 2 November 2009 (UTC)
 * Sean, your code doesn't work properly. (but mine doesn't either). Your code works until I enter an operator it doesn't understand. It says "invalid operator", which it should, but then when inputting 'Q' or 'q' for quitting, it no longer works. -- penubag  (talk)
 * I'm not on a system where I can test it, but my first reaction is that the scanf is probably reading in your newline(s). If so you'll need a case for ignoring spaces, newlines, etc.  Changing your error message to "printf("bad operator: '%c'\n", operator)" will help you figure out what's going on.  Also read about debuggers for your platform (MSVC or gdb, probably).  --Sean 17:41, 3 November 2009 (UTC)
 * That was the problem. After I add another printf("%c",c) it works fine. -- penubag  (talk) 21:48, 4 November 2009 (UTC)

ffshrine (2)
ffshrine is finally back up (why did they even take it down just for donations?), but it still has a problem. The download links on that site do not work. I click to download a song, but it does not start up; I right-click to download a song, but it does not download. What is causing this? jc iindyysgvxc  (my contributions) 08:46, 2 November 2009 (UTC)
 * Not familiar with that site. My first thought is that, if they shut down to encourage (or for lack of) donantions, then maybe it's a bandwidth issue? Downloads would logically be a big part of a site's bandwidth, I would think, and that can get pricey. UltraExactZZ Claims~ Evidence 19:56, 2 November 2009 (UTC)

wavelength???
can any one guide me how can i find wavelength of the colour by its image. 220.225.98.251 (talk) —Preceding undated comment added 09:44, 2 November 2009 (UTC).


 * From a photo in a JPEG file? Short answer: you can't. Even if you take into consideration all the colour space stuff, all the JPEG artifacts and the inaccuracies of cameras, a camera is only designed to capture light as we see them. A pixel records brightness of 3 colours, it doesn't record the wavelength (colour) of the scene. How do you know if orange is really orange or if it's just a mixture of red and green light? That's the long version of "you can't". --antilivedT 10:36, 2 November 2009 (UTC)


 * Conceivably, a multi-spectral image or a hyperspectral image could have sufficiently dense channel packing that it could useful for estimating particular wavelengths. However, conventional images (made on consumer cameras) produce only "red", "blue", and "green" channels - which are very vague, very broad ranges of wavelength sensitivities in each channel.  You could give a very wide range of wavelengths which would activate each channel, by checking the technical specifications of your camera's filters or CCD sensor response; but at best this will narrow down to a few hundreds of nanometers wavelength.  If you are attempting to do spectroscopy, a conventional 3-channel "color" image will not have the required information.  Nimur (talk) 19:53, 2 November 2009 (UTC)


 * This Kodak CCD technology review goes over the color response and shows the wavelength-vs.-amplitude response in the sensor for a particular model of camera (the Kodak DCS 620x model). In the strict sense, when you have an image, what you know is the channel amplitude (not the wavelength).  So you're trying to invert from RGB to amplitude-vs.-wavelength - in other words, "go backwards" from the data recorded in RGB form back to the physical wavelengths which triggered that response.  You would need to set up an inversion problem to solve for the most-likely wavelength(s) that gave you a particular RGB or CMYK value in your final image.  Whether this process will work depends on many factors - how much do you know about the image source; how orthogonal are the R/G/B channels; how underdetermined is your problem; but it could be done, and it might work for certain well-controlled image processing problems.  Nimur (talk) 19:59, 2 November 2009 (UTC)


 * If you're not aware of it already, note that although light of a particular wavelength has a particular color, it is definitely not the case that everything of a particular color is emitting a particular wavelength. In fact for most colored objects the object is emitting a range of wavelengths. Indeed, two objects can be emitting two completely different wavelength profiles yet appear to be exactly the same color. Color vision is a complex topic, due in part to the fact that eyes aren't true spectrophotometers, but are much simpler Red/Green/Blue detectors (even that's not quite correct, as it's more yellowish-green/green/blueish-violet detector, where the yellowish-green and green detectors have some activity in the violet end, and the blueish-violet detector picks up some red), which the RGB in the JPEG/GIF/etc. is trying to approximate. Unless you know that the source is monochromatic (i.e. it's from a scientific instrument - in which case see the answers above), the easiest option is to just compare the color visually with a similar photograph of the visible spectrum - the whole thing will be inaccurate anyway. Something like File:NASA_Hydrogen_spectrum.jpg is probably what you're looking for as a comparator. Keep in mind, though, that some colors (purple, brown, pink, etc.) can't be represented by a single wavelength, and need a mixture of wavelengths to produce. -- 128.104.112.149 (talk) 22:45, 2 November 2009 (UTC)


 * As others have correctly said - you can't do this properly. Just about the nearest you could get would be to convert the image into HSV color space (Hue, Saturation, Value) - and to observe the hue of the HSV value.  If you mapped 0 (red) to 620nm and a hue of maybe around 0.9 (violet-ish) to 400nm - then I suppose you'd be getting somewhere close to something kinda-sorta right.  That might get you a pure color that would look to the human eye somewhat like the color in the image source...but that's incredibly error-prone and I couldn't recommend it for most purposes.  SteveBaker (talk) 02:31, 3 November 2009 (UTC)

Viceo converter
Are there any open-source video converter programs that require neither codecs nor registration? jc iindyysgvxc  (my contributions) 11:51, 2 November 2009 (UTC)


 * ffmpeg, also gstreamer via gst-launch, but ffmpeg is more straightforward to use. --194.197.235.240 (talk) 13:08, 2 November 2009 (UTC)


 * handbrake, avidemux —Preceding unsigned comment added by .isika (talk • contribs) 13:25, 2 November 2009 (UTC)

diode snap-off
j'aimerai savoir ce que c'est une diode snap-off? ses structures, utilisations, caractéristiques et fonctionnement —Preceding unsigned comment added by 41.204.124.12 (talk) 13:57, 2 November 2009 (UTC)

Translation: ''I would like to know what diode snap-off is? Its structures, uses, characteristics, and function.'' -- Nimur (talk) 20:11, 2 November 2009 (UTC)


 * See Step recovery diode -- Finlay McWalter • Talk 15:19, 2 November 2009 (UTC)
 * Translation: Voir Step recovery diode, en anglais. Il n'y a pas une traduction en français. Merci,  gENIUS 101  15:43, 3 November 2009 (UTC)

bots
what scripting language are they made from?Accdude92 (talk to me!) (sign) 14:31, 2 November 2009 (UTC)


 * Assuming you mean web bots or Wikipedia bots. They can be made from just about any of them (and are aided by there usually being standard libraries that let you do routine tasks pretty easily, like parse web content). Python, perl, and PHP are pretty common for web bots. If you are interested in Wikipedia-specific bots, see Bots, especially this section for description of the many different languages that can be easily used. --Mr.98 (talk) 15:15, 2 November 2009 (UTC)

rss
I need a program that'll ding or do something to let me know when an rss feed updates. Any suggestions? —Preceding unsigned comment added by 82.43.88.201 (talk) 16:03, 2 November 2009 (UTC)
 * I presume many of the things listed as supporting RSS at Comparison of feed aggregators can do this particularly if they are decidicated as opposed to being a web browser or some such. Having said that it appears Safari does have some notification plugin and Firefox may also do notifications. Email clients with RSS support like Thunderbird would likely also support some sort of notification as they would for e-mail. The comparison page does include a column for 'tray notification' albeit most readers are listed as unknown Nil Einne (talk) 16:26, 2 November 2009 (UTC)
 * I use Alertbear. F (talk) 04:10, 3 November 2009 (UTC)

twitter
is there a way to view/download all the tweets for a particular user? either through twitter.com or 3rd party app? —Preceding unsigned comment added by 82.43.88.201 (talk) 20:14, 2 November 2009 (UTC)


 * No. Twitter only lets you view about the last 50 tweets by a user. After that, they get archived on the Twitter server but can't be viewed by any user.--el Aprel (facta-facienda) 03:46, 4 November 2009 (UTC)


 * You can definitely see more than 50. Click 'more' at the bottom of the user's page at twitter.com. I just tried this and viewed about 200 tweets for one user. --JoeTalkWork 17:25, 5 November 2009 (UTC)

DOS printing
Question moved from Talk:How to print from dos to usb printer prefix:Wikipedia:Reference desk/Archives. Astronaut (talk) 22:07, 2 November 2009 (UTC)

I have some DOS applications that insist on printing to a parallel printer port. However, my new printer only has USB. Where can I find a cable that can do this? (There are lots of cables that connect the computer's USB port to a parallel printer port but I need the reverse.) Alternately, are there any drivers that can fool the DOS applications into thinking that they are printing to a parallel port when they are actually printing to the computer's USB port. — Preceding unsigned comment added by 117.196.224.106 (talk) 12:19, 31 October 2009

You don't need a cable; DOS does not recognize USB. Assuming you have Windows XP or above, let it do the work: ---— Gadget850 (Ed)  talk 22:18, 2 November 2009 (UTC)
 * Install the printer under Windows
 * In the printer properties, share the printer with a logical name
 * Capture LPT1 by opening a command prompt:
 * NET USE LPT1: \\ \ /PERSISTENT:YES

Lossy compression
I'm practically terrified by it. Well, not terror...more of a creeping paranoia. I noticed a certain song of mine had a strange buzz in the background when I listened to it through the car speakers, and thus began the paranoia.

I'm starting to become concerned about my ~600 songs. They're either bought from the iTunes music store, ripped from CDs, or occasionally one downloaded (Touché! They were songs that could not possibly be bought!). I tend to be a perfectionist, and I can't stand the thought of my beloved music becoming crappier and crappier through the years. I've read through the article about lossless data compression, but I'm still not sure I fully understand. What exactly should I go about doing to ensure that my music doesn't degrade further?-- The Ninth Bright Shiner 22:31, 2 November 2009 (UTC)


 * See Lossy compression. It's a nice thought, but lossy is not lossy over time, but lossy at the point of encoding and thereafter stable. However pretty much any audiophile will prefer CD or vinyl to MP3. --Tagishsimon (talk) 22:35, 2 November 2009 (UTC)


 * Playing the music will not result in further loss. No need to worry. --Mr.98 (talk) 23:30, 2 November 2009 (UTC)


 * O RLY? That's quite the relief. I could have sworn reading something to this extent, though...somewhere. I'm not quite an audiophile yet, but I do prefer quality. Would the truest-to-the-original copy of a file have to be from the file itself; i.e., actually play the original CD in the car as opposed to ripping it and burning a CD? And upon ripping a CD, what would be the action to take to save it losslessly? (Tounge-twister.)


 * And while we're on the subject, what of images and videos? Any advice there, such as regarding scanning or taking a video?


 * I sure am asking a lot, aren't I? The finer details of files mystify me, like quarks mystify someone who's just taken high school chemistry. Thanks!-- The Ninth Bright Shiner 00:46, 3 November 2009 (UTC)


 * You only get loss when you compress and make a new file (basically). So when you make MP3s from CDs, you get some loss. You don't get any additional or cumulative loss just by listening to MP3s—the loss is a one-time affair (CD to MP3 = lossy compression). If you take the MP3s and make, say, AACs from them, you get loss (this is known as transcoding—converting from one format to another—and if you go to a lossy format, you get some loss). Every time you convert to a lossy format, you get loss. And indeed, transcoding can create a lot of loss, more than just making one file with a given number of loss, because the different algorithms are taking different chunks of the data out (they aren't taking advantage of previous algorithms' "savings").
 * Anyway, in most cases, there's a question of how much loss you can detect. If you have not-too-great speakers, a little loss will probably not be detectable. If you are a dedicated audiophile/hi fi dude, then maybe you care. Even in that instance, there are levels of compression and corresponding levels of loss. Personally I don't really have the ear or the equipment to distinguish between CD audio and 256kbps mp3s. But some people do, or claim to.
 * If you really don't want loss, you have use a lossless format, like FLAC. You can get programs that convert CDs to FLAC files and let you play FLAC files. They are HUGE files though—like, half a gigabyte for one CD. Still, some people go for them. Knock yourself out...! --Mr.98 (talk) 00:57, 3 November 2009 (UTC)
 * And there's probably too much to discuss about images and video, though Image file formats might be a place to start (also the not so great Container format (digital) - at the very least, there are the same lossy conundrums attaching to both topics. --Tagishsimon (talk) 01:04, 3 November 2009 (UTC)
 * Hey, with terabyte hard drives being churned out along with iPod Classics that could eat my own computer's hard drive, anything is possible! Although, is there any easy way to convert to lossless files that an iPod could play (i.e., Apple Lossless), or will it be needlessly complicated and riddled with caveats, like every other nitty-gritty file operation has been for me?
 * I'll poke around the articles for image and video compression, but they aren't that much concern. Thanks again everyone!-- The Ninth Bright Shiner 01:26, 3 November 2009 (UTC)


 * In theory you should be able to convert lossless to lossless and have it still be lossless. Apparently Max can do this. Never used it myself, though. --Mr.98 (talk) 01:57, 3 November 2009 (UTC)


 * I'm pretty sure FLAC is more efficient than that, after all a CD is only 700MB max. My CDs compressed to FLAC are usually 200-300MB per CD. --antilivedT 11:00, 3 November 2009 (UTC)


 * Well, maybe. I've looked at FLAC files on downloading sites and was amazed that it was basically half a gig per album. In general though I think we can just say that FLAC is about 10X more than high-quality MP3s. Which, again, is fine, if that's what you go for! --Mr.98 (talk) 13:20, 3 November 2009 (UTC)
 * As a rule of thumb, raw CD audio is 10 MB/minute, lossy-compressed CD audio is 1–2 MB/minute, and lossless-compressed CD audio is 4–5 MB/minute. FLAC's compression is a bit worse than most rival lossless codecs, but it has the advantages of being computationally cheaper and completely open (patent-free with a BSD-licensed implementation). -- BenRG (talk) 15:33, 3 November 2009 (UTC)
 * Personally, I can't really tell a difference in sound quality betwee CD and MP3. And I for one can't tell a difference between lossless and MP3. I know what it's supposed to be, but my ears just can't detect a difference. Anakinjmt (talk) 19:31, 4 November 2009 (UTC)


 * I have found that some cheap brands of recordable CD's sound like crap in my car player. I can only figure that the error rate is higher.  Verbatim makes some CD-R's marketed as being especially for car players, that if I remember right claim to have better temperature stability than typical cd-r's intended for use in home or office environments.  I've had good luck with ordinary good brands like Taiyo Yuden.  My guess is if you're hearing degraded sound, it's more likely from data errors than from the encoding algorithm.  But if you're ripping your own cd's, then yeah, rip to FLAC for long term archiving, even if you use mp3 for your portable or car players.  Storage space on large hard drives is practically free these days. 69.228.171.150 (talk) 01:43, 5 November 2009 (UTC)

Windows 7 64 bit and Alienware integrated webcam driver
Hi there. Does anyone know whether there is a driver which will enable the integrated webcam in my Alienware m9750 (which came with XP) to work with my new 64 bit Windows 7? I can't navigate Alienware's awful customer support services. Cheers, SGGH ping! 23:57, 2 November 2009 (UTC)
 * Its a "USB2.0 Camera" "Bison NB Pro" camera, whatever that means. Windows 7 knows that its there, and knows what it is. It lists it there under devices and printers, however it just shows a white box when I try to use it. SGGH ping! 00:05, 3 November 2009 (UTC)