Wikipedia:Reference desk/Archives/Computing/2009 August 14

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August 14

GSM and UMTS required bandwidth

How many 200 khz gsm channel pair (DL/UL) and how many umts channel pair do you need to have -all- the channel required to make a single phone call? (and if possible a breakdown of all channel required a minima for making a -single- phone call). I know the list of all the channel type but I wondered what would be the minimal requirement to pass one single phone call (I'm not sure it's the "right" section, but I think cellular is networking related isnt it?) - Esurnir (talk) 00:42, 14 August 2009 (UTC)

One GSM channel can carry 8 phone calls, UMTS uses cdma and because of that (and greater bandwidth (it was 5MHz, if i remember correctly)) can carry more, although i do not know how much exactly. -Yyy (talk) 15:36, 15 August 2009 (UTC)

I know it can carry up to eight user channel but then you also need a certain number of control channel access channel and broadcast channel just to setup one call. I'm wondering how many in total are needed. What is the minimum infrastucture and how many per call. —Preceding unsigned comment added by 24.114.234.36 (talk) 17:40, 17 August 2009 (UTC)

Use of standalone Google Maps utility

When I try to use the standalone Google Maps utility I just downloaded, it is unable to connect to the server. I have tried the test diagnostics it suggests and it comes up with:

Google Earth Server Test

kh.google.com UNSUCCESSFUL

maps.google.com SUCCESSFUL

auth.keyhole.com SUCCESSFUL

I have AVG on my computer but I can't see an option for allowing access to Port:80 (which has been indicated as being the problem). Other than that, just the Windows firewall itself (again, can't see any pertinent options). Regards -- Alexandr Dmitri (Александр Дмитрий) (talk) 03:10, 14 August 2009 (UTC)

AVG just updated itself and now Google Earth (not Google Maps as I incorrectly stated) now works -- Alexandr Dmitri (Александр Дмитрий) (talk) 15:06, 16 August 2009 (UTC)

Filtered websites

Could people from the UK test whether they can connect to 4chan.org for me, or if it gives a Network Timeout error. I have a horrible feeling the UK is filtering websites again, much like they did to that wikipedia article. Thanks

It works fine for me here in Norwich Zzubnik (talk) 09:35, 14 August 2009 (UTC)

hmmm, any idea what might be causing my problem? I could access it three hours ago and now all I get is a network timeout error. I've tested using a proxy and I can access that way (very slow) so I guess it must be me. I've tried a dns flush and that hasn't helped. —Preceding unsigned comment added by W.Butt ACKACK (talk • contribs) 09:55, 14 August 2009 (UTC)

Has the UK filtered Wikipedia articles? --Andreas Rejbrand (talk) 12:10, 14 August 2009 (UTC)

I believe the OP is referring to the incident mentioned in this article. --LarryMac | Talk 12:29, 14 August 2009 (UTC)

TrueCrypt, encrypting entire drive on dual boot PC

According to the TrueCrypt article, The version for Windows Vista or XP can encrypt the boot partition or entire boot drive.... If I encrypt the entire boot drive of a dual boot laptop (Xp and Xubuntu), what will the boot sequence be? Will I first get a prompt for the TrueCrypt password, and then get the grub startup menu, or vice versa? Has anyone here tried such a setup? --NorwegianBlue ^talk 09:03, 14 August 2009 (UTC)

Encrypting the entire drive won't work since TrueCrypt's boot-time decryption only works in Windows, as far as I know. But you can encrypt the Windows and Linux partitions independently using the TrueCrypt bootloader for Windows and a small unencrypted boot partition for Linux. I recommend searching the TrueCrypt forum for the phrase "dual boot". It looks like one setup has TrueCrypt loading GRUB and another has GRUB loading TrueCrypt. -- BenRG (talk) 17:03, 14 August 2009 (UTC)

That was helpful. I hadn't specifically searched the TrueCrypt forums, and the links that turned up on a general google search were quite confusing. The ideal solution, from a user point of view, would IMO be to first say hello to TrueCrypt, and then select the OS to boot with Grub. But after a bit of thought, I realize that the TrueCrypt bootloader would then have to somehow communicate the decryption algorithm to the OS. There is no layer between the hardware and the OS where TrueCrypt could reside and do its thing, in order to permit OS-independent encryption. Pretty obvious now, but it wasn't, to me, when I posted the question. Thanks, --NorwegianBlue ^talk 19:24, 14 August 2009 (UTC)

There is such a layer early in the boot process: the BIOS disk functions. I'm not certain that TrueCrypt's bootloader hooks them or that that would be enough to support GRUB, but it's not inherently impossible. Ask at the TrueCrypt forum—someone must have tried it before. -- BenRG (talk) 11:02, 15 August 2009 (UTC)

Thanks! --NorwegianBlue ^talk 15:32, 15 August 2009 (UTC)

Weird spam

Just in the past couple weeks I have been receiving increasing amounts of a certain kind of spam, which I am having trouble understanding. It isn't a big deal, since my spam filter for the most part is working pretty well, but they are kind of intriguing. For one, my email address is never mentioned in the 'To:' field. It is always 'sent' to something untrue like 'info[at]mail[dot]com' or 'nothingmuch[at]woobling[dot]org'. Another thing is that these emails don't even have any links in them, so I can't possibly conceive what kind of benefit they are providing the sender, except he's sending me, maybe she's sending me just to see me get irate. Here are some screenies: [1] [2]. Any thoughts? —Akrabbim^talk 12:24, 14 August 2009 (UTC)

Well, they might want you to respond—they might be phishing attempts of some sort. Or they might just be Bayesian poisoning. --98.217.14.211 (talk) 12:56, 14 August 2009 (UTC)

The email message may also be an effort to identify whether you are a human or a machine - by opening the mail, you may be loading (transparent) images from a web-server, which can uniquely identify your email address as a valid (and therefore, to-be-targeted) address. Our spam article has a brief mention about this tactic. Nimur (talk) 16:18, 14 August 2009 (UTC)

Maybe, but that isn't true in this case. Gmail tells you if there are images from an address that you have not received from before. At this point I'm more interested in how they are even getting to me if I am not in the 'To:' or 'CC:' fields. —Akrabbim^talk 16:31, 14 August 2009 (UTC)

On the last point: that is because they are putting your address in the Bcc field, or rather doing the equivalent thing in their spam-generating software. AndrewWTaylor (talk) 16:39, 14 August 2009 (UTC)

Yes, sorry, I thought that was fairly clear. You can send messages quite easily without the address of all the recipients being displayed. Bcc is quite useful for things like mailing lists -- that same message probably went to a hundred addresses, and if someone mistakenly hits "reply all" to say, "Hey, is this spam?" then you're getting EVEN MORE lousy, useless mail. --98.217.14.211 (talk) 17:04, 14 August 2009 (UTC)

I don't think reply all works with bcc. 195.35.160.133 (talk) 11:40, 18 August 2009 (UTC) Martin.

javascript - browser dependent

Is there a reason why this http://www.w3schools.com/js/tryit.asp?filename=tryjs_confirm doesn't work in google chrome? is it valid to use document.write from a popup box anyway?83.100.250.79 (talk) 17:51, 14 August 2009 (UTC)

It doesn't work in Safari, either, for that matter. I'm not sure what you're takling about regarding the popup box -- the fact that it uses the result of a confirm() to determine what to write is not a big deal at all. It's definitely something about document.write, though -- if you change it to document.body.innerHTML = whatever, then it works fine. --98.217.14.211 (talk) 17:56, 14 August 2009 (UTC)

""popup"" meant subroutine called via dialog box .. not very clear..

For some reason, if you don't put a <html></html> around the response text, it displays as blank in Safari. Which is weird and probably wrong. --98.217.14.211 (talk) 18:06, 14 August 2009 (UTC)

Both are from webkit - but is webkit wrong? or just not doing undefined behaviour?83.100.250.79 (talk) 19:16, 14 August 2009 (UTC)

using .innerHTML makes sense to me. What I don't get is the use of document.write - I'd expect it to append the document, not overwrite - which is what it does when the <html></html> tags are used (ie it overwrites).

It's not clear to me that document.write is actually defined in this context - ie write to where? But the example is from an offshoot of the W3C standards body - I'd expect it to be right.

Does anyone have a clear idea of what document.write should have done in the above example?

If you call document.write after the document object is written (e.g. the whole page has loaded), it essentially rewrites the entire document—all elements. It's only useful in situations where you are generating an entirely new page from scratch with Javascript (mostly used for outputting new windows and things like that). .write doesn't append unless you call it while the body is still loading (e.g. if you slip in a document.write("hello!") in script tags in the body of your HTML, it will do so); if you want to append text, you have to be more specific than editing the entire document object, generally speaking. What's weird about the webkit approach is that it gives a blank page when it just has a text string -- it should render the text string in the default font (like Firefox), or, at least I imagine it should. --98.217.14.211 (talk) 19:26, 14 August 2009 (UTC)

That makes sense - I was thinking that the .write method continues to append the web page even when loaded (and therefor somewhow infers the current 'caret' of text insertion ie looking for a close </script> and popping back along the call tree until it finds a point where plain text is the context .. clearly fraught with problems)...

I don't understand what webkit is doing either. If I save a text string as .html and open it with the browser it does manage to display it.83.100.250.79 (talk) 20:17, 14 August 2009 (UTC)

It looks like webkit does an initial error checking pass when opening a web page - eg the textfile "Hello" seems to be automatically encased in html and body tags. (it also seems to add closing tags were they are 'optional' and forgotten.)

I'd assume that it doesn't go through this process when re-writing the page after it's been opened - hence the new file "you pressed ok" results in blank since the display mechanism never finds the first html..83.100.250.79 (talk) 20:32, 14 August 2009 (UTC)

Well, that sounds plausible. Weird. I imagine this sort of thing just doesn't come up that much in the real world, because you're rarely rewriting entire pages with Javascript after they have loaded (if you are.... you've made some bad developer decisions!). --98.217.14.211 (talk) 04:36, 15 August 2009 (UTC)

Yes :) 83.100.250.79 (talk) 10:40, 15 August 2009 (UTC)

Resolved

Lost in PHP

Hi All,

I'm getting frustrated! Can't figure out this simple line fails with Fatal error: Function name must be a string ?

$txt = $_GET['find'];
$txt = $str_replace(" ","%",$txt); // <-- this line
echo 'Looking for : '.$txt;

the url being passed is test.php?find=abc+def

Note: when I have it just echo 'Looking for : '.$txt; it shows the '+' replaced by space, so I assume in the text to replace I should be looking for spaces.

Someone please enlighten me :( PrinzPH (talk) 18:10, 14 August 2009 (UTC)

You shouldn't have the $ in front of str_replace. See the examples here --LarryMac | Talk 18:15, 14 August 2009 (UTC)

Resolved

O.. M.. G.. and to think that was the where I got the syntax from in the first place ^_^" sigh... as Danny Elfman sang: "THE LITTLE THINGS!"... THANKS A HEAP LarryMac! PrinzPH (talk) 18:57, 14 August 2009 (UTC)

Facebook Loading Error

When I open Firefox (all software on my computer is up to date) and I log in to Facebook, my home page shows up just fine. But, whenever I click a link (be it through Notifications, or some other Facebook related link) it loads the generic Facebook page (with the Home, Profile, Friends & Inbox bar on top, with the notification and chat bar on the bottom) but then loads nothing else. I have no issue loading any other website, and I can link to Facebook from an external site and load the page just fine.

Why is this?

Hubydane (talk) 19:13, 14 August 2009 (UTC)

Try making sure your cache is emptying, first off. (Clear your history and caches out.) See if that fixes it.

If not... I've noticed that for me, at least, many, many, many sites, Facebook included, are really, really, really poor at rendering. I used a debugger to see what the holdup was -- it was in every case scripts being loaded from other sources that were holding it up (e.g. Google Analytics, or advertisements, and things like that). The browser would render maybe half the elements and then wait for these scripts, which often would time-out anyway (god knows why). So I installed NoScript for Firefox and was able to tweak the settings so that ONLY local scripts would be processed. I found that it SIGNIFICANTLY improved rendering time on most pages, though of course it broke some pages as well (though it is easy enough to set NoScript to ignore those pages). Anyway, that might be worth trying, just to see if it helps out. --98.217.14.211 (talk) 14:38, 15 August 2009 (UTC)

Are you running an ad blocker? Sometimes Adblock Plus causes load problems like that. --jpgordon^{::==( o )} 15:34, 15 August 2009 (UTC)

Merging audio channels

I want to create surround audio simply by selecting different audio clips for each speaker. Is there any application that lets me do this simple task? --81.227.70.94 (talk) 21:40, 14 August 2009 (UTC)81.227.70.94 (talk) 19:54, 14 August 2009 (UTC) Try Audacity 88.108.14.227 (talk) 17:54, 20 August 2009 (UTC)

copying from cd

some times i want to copy some simple video from video cd ,i got message ,"invalid Ms dos function -------" how can i overcome this and by which techinique i can copy these videos. Also how can i create cd of videos having this property. —Preceding unsigned comment added by 119.154.20.223 (talk) 20:23, 14 August 2009 (UTC)

Video CDs use a strange disc format that's different from the usual data CD format. You need a Video CD ripping program. I don't know what to recommend, but I'm sure you can find something with a web search. The video data once extracted is just MPEG-1, which practically any movie player can handle. For making Video CDs you likewise need software with special Video CD support, but I think most CD burning software does support it. There's probably not much use making Video CDs these days because MPEG-4/"DivX" AVI files are much better and most set-top players now support them. -- BenRG (talk) 21:26, 14 August 2009 (UTC)

HID DATA Has Stopped Working

HP G60t or something like that, brand new. Bought a Windcomm bluetooth thing (little USB plug that let's me bluetooth) and installed it (had to uninstall then re-install because my i forgot my phone's ID), now every time i start up i get this error message "HID DATA has stopped working."

I'm running Windows Vista x64. Bluetooth and everything seems to work fine, I just want the message gone. o_O —Preceding unsigned comment added by Hubydane (talk • contribs) 21:57, 14 August 2009 (UTC)

Gravit On Mac OS X

Does anyone know where I can get a pre-compiled Gravit for Mac OS X? --Melab±1 ☎ 22:09, 14 August 2009 (UTC)

It looks like the Gravit developer is planning to release one "soon." I tried to compile this just now, only to learn once again why I hate Mac OSX - it's a confusing mess. It seems that by default, OSX has a system library, a Framework, and an X11 version of the libGL OpenGL. All of these are conflicting with each other; and they conflict with the actual SDL library desired by Gravit. (In short - it's nontrivial to make this program compile on a Mac, though it appears possible). Nimur (talk) 23:24, 14 August 2009 (UTC)

I haven't really tried to compile on Mac OS X and haven't got into its structure, so I can't say anything about it being a mess. All I know is that I like Windows better because I don't have to use complicated button pressing and dragging to copy or move a file in Windows Explorer, I have access to Visual Studio, there's a lot more available software, and a hole bunch of other reasons. --Melab±1 ☎ 03:27, 20 August 2009 (UTC)

nvidia file permission reseting after boot

basically i need to set the user on /dev/nvidia* (two files) to user "boinc" (to get boinc to register my CUDA graphics card) and i do that via chown but i found that the permissions reset after each boot. running "ls -l | grep nvidia" inside /dev shows that both files reload with "crw-rw-rw-. 1 root root..." (so i cant add boinc to the group "video") i edited /etc/security/console.perms.d/50-defaults.perms and removed the line starting with <dri>, and rebooted but still no look, i also have SeLinux disabled and running fedora 11, any help?--90.197.244.113 (talk) 22:20, 14 August 2009 (UTC)

I had a similar problem; Fedora doesn't seem to allow init scripts to chown files in /dev/. I think our workaround was to manually initialize the NVIDIA card with a script, something to the effect of

# Create /dev nodes for nvidia devices
function createnodes() {
   # Count the number of NVIDIA controllers found.
   N3D=`/sbin/lspci | grep -i NVIDIA | grep "3D controller" | wc -l`
   NVGA=`/sbin/lspci | grep -i NVIDIA | grep "VGA compatible controller" | wc -l`

   N=`expr $N3D + $NVGA - 1`
   for i in `seq 0 $N`; do
       mknod -m 666 /dev/nvidia$i c 195 $i
       RETVAL=$?
       [ "$RETVAL" = 0 ] || exit $RETVAL
   done

   mknod -m 666 /dev/nvidiactl c 195 255
   RETVAL=$?
   [ "$RETVAL" = 0 ] || exit $RETVAL
}

This handled our CUDA and non-CUDA cards, automounted them, and set the permissions on them. But we have to manually run this (with superuser permission "sudo"), after booting. Nimur (talk) 23:31, 14 August 2009 (UTC)

(EC) I was going to suggest just adding "chown boinc /dev/nvdia*" to the end of /etc/rc.local, but Nimur says Fedora has the bizarre behavior of not letting you do that in an init script. I personally would give it a shot anyway and try to debug that "feature". --Sean 23:56, 14 August 2009 (UTC)

By all means, I agree with Sean's suggestion in principle - except that it didn't work! If you figure out how to make it work, please post an update, and let us know (it'll streamline our reboot process!) Nimur (talk) 00:08, 15 August 2009 (UTC)

Aren't you supposed to set the /dev/nvidia* files to be owned by root, but with a group of "video" and permissions crw-rc----, then all users that need to access those devices are set up to be members of the "video" group (via /etc/group). That's the right thing for accessing the card as a mere user with OpenGL or whatever...I have no clue about CUDA though. SteveBaker (talk) 03:00, 15 August 2009 (UTC)

CUDA uses the graphics accelerator for non-video computation, so the "video" group is not suitable - user processes also need access. Nimur (talk) 04:06, 15 August 2009 (UTC)

several hours of google latter i've found how to reset the permissions, add to /etc/modprobe.conf,

options nvidia NVreg_DeviceFileUID=0
options nvidia NVreg_DeviceFileGID=91
options nvidia NVreg_DeviceFileMode=0660
and i added boinc to the video group and use the video group GID in modprobe, but boinc doesnt want to play ball--90.197.244.113 (talk) 11:10, 15 August 2009 (UTC)

it appears now, i can set boinc as either owner or group/in a group, for the /dev/nvidia* via modprobe.conf,then after rebotting the pc boinc will only recognise the cuda card if i then restart the boinc service, any ideas either to fix this bit now or on how to automate restarting the service?--90.197.244.113 (talk) 16:43, 15 August 2009 (UTC)

claiming a domain name

When my church acquired a domain name it was registered to an individual, the owner of the small company which was providing the Internet connection. The company went out of business and he could not be found to transfer ownership of the domain name. The registration expired a few days ago. Web hosting companies such as Go Daddy offer to back order the domain name; this actually means that when the name becomes available the company would enter a bid on the customer's behalf. How long would it likely be before the name is released? --Halcatalyst (talk) 23:00, 14 August 2009 (UTC)

It could be on the order of years; top level domain names can be purchased for at least 2 years. It's much easier if you can track down whoever originally registered it and transfer it directly, rather than waiting for the name to expire and "back-ordering." Nimur (talk) 23:26, 14 August 2009 (UTC)

As I mentioned, the registration is now expired. The question is, how long will it take before the name is made available again? Thanks. --Halcatalyst (talk) 23:32, 14 August 2009 (UTC)

If the registration has expired, isn't the DNS name available now? Are you sure you don't mean that the hosting has expired? A DNS name can point to a non-operating server for a very long time. Nimur (talk) 23:38, 14 August 2009 (UTC)

It looks like ICANN allows a maximum of one transfer of ownership within 60 days. If the domain has just expired, there is a 45-day grace-period to allow it to be renewed by the original owner; and then it can be transferred on the open market. Sorry for my earlier comment; the domain is not available immediately. Nimur (talk) 23:51, 14 August 2009 (UTC)

Thanks, that's the information I needed. One more thing: are the rules any different for .org as opposed to the others? --Halcatalyst (talk) 00:06, 15 August 2009 (UTC)

I've been through exactly this situation recently. http://sjbaker.com became available (I've had http://sjbaker.org for years) - I had to wait 45 days after it expired before I could purchase it. Then I had to wait 60 days before I could transfer it from the domain registrar who sold it to me to my regular registrar. Now, if only the owner of http://stevebaker.com (who has a pretty crappy site) would give it up! SteveBaker (talk) 02:56, 15 August 2009 (UTC)

No telephone provider for the web?

Do you need a telephone provider to have the internet? Once the telephone line is connected to your computer do you need a provider (e.g. AT&T) to have the web in additional to your ISP? • S • C • A • R • C • E • 23:30, 14 August 2009 (UTC)

You can connect to the internet in a variety of ways. A telephone-line based modem is usually called an ISDN or dial-up access connection, and is rapidly becoming obsolete in most parts of the world. There are other technologies, generally called broadband internet. For historical reasons, many broad-band internet providers evolved out of telephone companies; but they also came from cable television conglomerates, as well as other "data-only" network provider companies.

If you choose to use a telephone line for dial-up access, you still need a service provider (usually this involves an hourly- or monthly-fee in addition to the charges for making the phone calls). It is certainly possible to have a separate ISP company providing the dial-up service, and a different company providing the telephone service; but more often, your telephone company will also sell internet service (for your convenience). If you don't have telephone service, then connecting the wire to your computer will not allow you access; conversely, if you don't have an ISP providing a computer on the other end of the phone-line, the computer can be connected to the telephone network but will not be on the internet. Nimur (talk) 23:45, 14 August 2009 (UTC)

It depends on what services are locally available. I use cable internet and have no telephone provider whatsoever—all of my internet comes through my cable television connection. (And before you ask—in my particular situation, I could definitely have gotten internet without television, though the wiring for both is identical and would have had to been installed had it not already been, as is of course quite common in the U.S. at least. As it stands, I get a discount on the television for getting the internet, so it doesn't add up to a whole lot more to add that on.) --98.217.14.211 (talk) 04:23, 15 August 2009 (UTC)

Like 98.217.14.211 I had cable television with Numéricable and the Internet connection was an add on when I lived in Paris. Here in Morocco, Wana offers wireless connection using a receptor connected to a USB port (in French). Reception varies according to location and connection speeds according to the time of day. I'd be surprised if this didn't exist in other countries. -- Alexandr Dmitri (Александр Дмитрий) (talk) 11:19, 15 August 2009 (UTC)

There is definitely celluar wireless internet in the US but it is rather expensive and pretty slow. (You'd be surprised, I believe, at how backwards US cellular infrastructure is compared to Europe...) --98.217.14.211 (talk) 00:50, 16 August 2009 (UTC)