Wikipedia:Reference desk/Archives/Computing/2012 August 20

= August 20 =

The Ubuntu interface along with Kubuntu and toggle back and forth without rebooting?
I am a Windows7 user who know next to nothing about Linux. Every "once in a while" I try out some Linux Live-CDs to get a glimpse of the kind of onscreen environment other people are using every day. And I have kept wondering: If Kubuntu is based on Ubuntu, then why can't I have both? (and toggle between the two?) Is it technically totally impossible? Or is it more of a: "The Kubuntu people dislikes the Ubuntu interface and therefore block it"? --89.9.197.179 (talk) 03:45, 20 August 2012 (UTC)


 * Kubuntu is merely Ubuntu running a KDE desktop environment, and Ubuntu (the one downloadable from here) is Ubuntu running a GNOME desktop environment. The installation of desktop environments is trivial, and you can switch between KDE and GNOME at the login screen. → Σ σ  ς . 03:56, 20 August 2012 (UTC)


 * Aha! But then my question becomes: Is it absolutely necessary to log out to change the active desktop environment? (I would like to keep all active applications running uninterrupted so I can avoid having to go offline from any ongoing live conversation I have with other people on the net, who probably were the ones prompting me to try out "this or that" in the other desktop environment). -- (OP) 89.9.214.107 (talk) 07:22, 20 August 2012 (UTC)


 * No, it's not necessary. You can probably still do most of this through lightdm or GDM with fast user switching, but I haven't ever used it.  You can always modify   and run   and a number of other approaches. ¦ Reisio (talk) 12:37, 20 August 2012 (UTC)


 * Uh-oh! I did get the: " No, it's not necessary. "-part of the answer, Thank You! :-), but I guess I should strike out the "next to" (in my question) and plainly admit that: " I know nothing about Linux (nor Windows) " ;-( Could you please "translate" the rest of the answer? ;-) (And maybe expand a little on the " ..do most of this... ". So that I may get a tiny grasp on what it is that will stop me from keeping all active applications running uninterrupted in order not to loose any logged in connections or miss out on any part of a streaming data flow that I may be saving to disk at the time). -- (OP) 89.9.209.62 (talk) 16:21, 20 August 2012 (UTC)


 * Sorry I don't use Ubuntu much. You'd probably get the fastest help by going here: http://webchat.freenode.net/?nick=gnomKdeFasSwitch&channels=#ubuntu (type in the CAPTCHA, when you see ' ' in a tab at the top, you're in the right place.  I'm guessing you can either click on your user name somewhere in the panel (top right?) to switch users, or you might have to run   from a terminal (CTRL+ALT+t) and then switch from the screensaver after locking (sorry GNOME changed this recently and I haven't kept track, you can probably lock from one of those menus somewhere).  The KDE package is called , you can install it from your package manager as usual. ¦ Reisio (talk) 00:10, 21 August 2012 (UTC)
 * Thanks! -- (OP) 89.9.214.129 (talk) 18:15, 24 August 2012 (UTC)

Looking for an architectural model for a typical home Wi-Fi router
I'm looking for a reference architectural model for a typical home Wi-Fi router. It may be in the form of a functional block diagram with sufficient granularity/details. I need something that will help me reason about the workings (and limitations) of home routers. In my mental model, a home router implements a wired LAN and a wireless LAN, and the two are connected by a bridge; I'm not sure if a real device actually behaves like that. There are a few other things I want to figure out. Having a good and correct model goes a long way. Thanks in advance for your help. --98.114.98.196 (talk) 04:14, 20 August 2012 (UTC)
 * Typically they are small Linux computers with two network interfaces and appropriate routing and firewall rules. You have to understand a bit about network administration to get deeper than that.  OpenWRT and several related firmware replacements run inside those things, so those articles might help you. 69.228.170.132 (talk) 06:05, 20 August 2012 (UTC)

Convert OST to PST File
Hi, My OST File damage due to virus attack, so i am not open this OST file in proper way. So i want convert OST file to PST file, please help me...... — Preceding unsigned comment added by Krisdonaldo (talk • contribs) 10:11, 20 August 2012 (UTC)


 * How does this damage manifest? ¦ Reisio (talk) 12:40, 20 August 2012 (UTC)

Microsoft vs. Netscape
Did microsoft pay people working at netscape to sabotage their own product? Thanks.Rich (talk) 15:35, 20 August 2012 (UTC)


 * The main accusations were not related to sabotage, though there were some imputations of sabotage, though they were more related to Microsoft changing Windows to be incompatible, not with paying off rival employees. --Mr.98 (talk) 15:50, 20 August 2012 (UTC)
 * Microsoft changed some of the underlying APIs and some of the undocumented features on which Netscape relied. Microsoft did however pay to have roughly 10x the number of programmers working on the browser as Netscape had.Smallman12q (talk) 00:24, 21 August 2012 (UTC)
 * And 10x the lawyers, I'm guessing. ¦ Reisio (talk) 00:43, 21 August 2012 (UTC)
 * Probably 100x. And half the "programmers" are lawyers-in-disguise, too... - ¡Ouch! (hurt me / more pain) 08:16, 22 August 2012 (UTC)

canon 650d, Magic Lantern
I need to know which is the actual video recording bitrate of the 650d Someone know if there is magic lantern support for it in this moment? Thank you Iskánder Vigoa Pérez 15:51, 20 August 2012 (UTC) — Preceding unsigned comment added by Iskander HFC (talk • contribs)


 * The wiki for Magic Lantern does not list that model. Searching the Magic Lantern development mailing list suggests that it isn't supported. -- Finlay McWalterჷTalk 16:05, 20 August 2012 (UTC)

and what about the video bitrate recording?? thank you for answer — Preceding unsigned comment added by Iskander HFC (talk • contribs) 16:11, 20 August 2012 (UTC)


 * If you have a video generated by the device that you can share, this can easily be determined. ¦ Reisio (talk) 00:14, 21 August 2012 (UTC)

What, specifically, is wrong with this PDF file?
The National Nuclear Security Administration posts PDF files online as a response to Freedom of Information Act requests. Almost all of them have at least one page that triggers an error in any program I use to view them. Acrobat specifically says "Insufficient data for an image."

Here is an example of a file which triggers this: http://www.nnsa.energy.gov/sites/default/files/nnsa/foiareadingroom/RR00507.pdf

Page 1 of that file always gives me the above error. I've tried using pdftk to extract the page and uncompress it — it seems to have lots of binary data in it. But nothing can process it — not Acrobat, not Preview, not ImageMagick. The best any of them do is silently throw an error and load a blank page. It shouldn't be blank; it probably ought to look like this, more or less. (Note that page 2 of that second file throws the error, as does page 4, 6, 15, 17, 19, 22, 23, and 26. These are rampant errors — nearly a third of the pages in that PDF are unreadable.)

Can anyone take a look at the page and/or file to figure out what's likely wrong with it? It's something systemic to the NNSA's PDFs, and I'd be curious (heck, maybe even they'd be curious) as to what it's origin is. There would be something deliciously disturbing about the idea of them (the guardians of the nuclear secrets) having some kind of virus or corrupt hard drive or something. --Mr.98 (talk) 21:38, 20 August 2012 (UTC)


 * Looking at EE00507, Okular, Evince, Inkscape, and Gimp (which I think all share the same Poppler PDF library) complains about various invalid data, but will display (in what looks correct) all but pages 6,7,8 and 15. They report Error: PDF file is damaged - attempting to reconstruct xref table (with subsequent errors probably a result of that attempt being unsuccessful). -- Finlay McWalterჷTalk 21:58, 20 August 2012 (UTC)


 * And (again for EE00507) I get the same (blank) results as you (that is, worse than poppler) with Acrobat 8 Standard, Foxit 3.3, and Google Chrome (the last of which I think uses Google's PDF library not Adobe's) all on Windows. -- Finlay McWalterჷTalk 22:08, 20 August 2012 (UTC)


 * And it actually makes ghostscript (pdf2ps) coredump, after it too complains of a corrupt XREF table. -- Finlay McWalterჷTalk 22:12, 20 August 2012 (UTC)


 * And pdf-tools "repair" function says it's "not a correct PDF". -- Finlay McWalterჷTalk 22:22, 20 August 2012 (UTC)


 * If you're interested in what mad system created the corrupt PDF, its meta-info says it was scanned on a Canon DR-7580 in TWAIN mode, and rendered to pdf By Adobe Acrobat 6.0.2 Paper Capture - a toolchain one would have thought would produce good PDFs. -- Finlay McWalterჷTalk 22:25, 20 August 2012 (UTC)


 * Might have thought, anyways. If you've ever done anything with gs on a PDF generated by Adobe software, you know just how well Adobe "supports" its own spec. :p ¦ Reisio (talk) 00:40, 21 August 2012 (UTC)


 * Fails in Adobe Reader (not Acrobat/Pro) 6.0.2 as well. They're probably just doing something wrong in the scanning/assembly process and have no review process (which is deliciously disturbing given the source). ¦ Reisio (talk) 00:42, 21 August 2012 (UTC)


 * I think something converted DOS/Windows newlines (0D 0A) to Unix or Mac newlines (0A or 0D) in the compressed binary data. This would explain why the XREF table is corrupt (it contains byte offsets into the file, which would be wrong after the conversion) and it would explain why about 1/3 of the pages are corrupt (most pages have about 20K of compressed data, and the probability of 0D0A occurring is about 20K / 65536).


 * You'd expect a file the size of RR00507.pdf to contain about eight 0D 0A sequences. In fact it contains one, which straddles the end of a binary stream (PDF files are a mixture of binary and text; the 0D is the last byte of a binary stream, and the 0A is text). This seems to mean that whatever did the munging was somewhat aware of the PDF file structure. The textual parts of the file contain both 0A and 0D as newlines (e.g. the first line ends with 0D but the second line ends with 0A). This file must have been produced with a bunch of different tools, one of which is broken. Only the person responsible for the tools can figure out which one.


 * Since the number of munged byte sequences in each binary stream can be detected and is usually small, it would be possible to write a utility that repaired most of the pages by unmunging each stream in all possible ways and running it through a JBIG2 decoder to test for corruption. It would be a fair amount of work, though. -- BenRG (talk) 00:44, 21 August 2012 (UTC)


 * This may be a stupid question, but would it be possible to extract the JBIG2 stream and simply re-encode it into a PDF? That is, it seems to me like you're saying the problem is with the PDF structure, not the image data. Is there a straightforward way to repair that? --Mr.98 (talk) 15:08, 21 August 2012 (UTC)


 * It seems that all the readers are trying to follow the offsets in the file described by the XREF table. When they're discovering that the data at the end of some doesn't look like a valid JBIG2 stream, Acrobat and chums are just giving up. It looks like Poppler is being more aggressive, and trying to linearly scan for what it thinks are JBIG streams - which is why Poppler is having more success than Acrobat. For those that even it isn't decoding properly, those would seem to be where there is a corruption in the JBIG2 streams themselves. BenRG's theory sounds promising; if it's not that I'd bet it's some equally dumb automatic munging, where some system is trying to escape stuff in a binary file or redacting what it foolishly imagines to be a naughty word. Figuring out that corruption, and reversing it, doesn't seem like a straightforward thing to do. -- Finlay McWalterჷTalk 16:05, 21 August 2012 (UTC)


 * I think the JBIG2 streams themselves are corrupted. They contain no 0D 0A sequences, which is statistically very unlikely (there are none in RR00508.pdf either). If it was just the XREFs it would be no big deal since you can always read the whole file to find the objects, and I assume that's what some of the PDF readers do when they notice the XREFs are broken. The XREF values are way off, not just slightly off, so I think newline conversion happened in the textual parts of the file also, but that's okay since PDF allows any of the three newline types.


 * Anyway, the only thing to be done is to contact someone responsible and get them to fix it. I don't want to give legal advice but I'm pretty sure they're not fulfilling the requirements of the FOIA right now. -- BenRG (talk) 19:35, 21 August 2012 (UTC)

Glitching/skipping CD
Could anyone suggest as to why an (apparently) brand new unscratched/unmarked factory-pressed audio CD might play through absolutely fine in my regular stereo, yet have one track on it that glitches and skips in the same place every time when played in my PC's (Windows XP) DVD-RAM drive? I've tried different audio player software but it does it on all of them. Also, if I try to rip the track to mp3 using iTunes (with error correction enabled) the resultant file has mess in exactly the same places. Is there anything you can think of that I could try, without installing another CD drive (because I don't have one handy at present) that might fix this issue? --Kurt Shaped Box (talk) 22:09, 20 August 2012 (UTC)


 * Sorry, but it sounds like the computer DVD drive is the problem. Does it have this problem with other music CDs ?  If not, it might be an instance of the double tolerance problem (don't we have an article on this ?).  This is where both the CD and the drive are within tolerances to work separately, but both so close to the limit that the combo doesn't work. StuRat (talk) 22:15, 20 August 2012 (UTC)


 * I don't recall it ever doing this with other CDs in this way before. On a couple of occasions, I've ripped a CD, only to hear glitches on one of the produced mp3s - but then when I've ripped the disc again after giving it a wipe over, everything's been fine (so this might be unrelated). --Kurt Shaped Box (talk) 22:19, 20 August 2012 (UTC)


 * If you do want to rip this particular disk using your current drive, you could try a ripping application that targets accuracy over speed - such as Exact Audio Copy, cdparanoia or cdda2wav. Cheers,  d avid p rior  t/c 22:31, 20 August 2012 (UTC)


 * Well, I tried EAC. After taking 30 minutes to rip the track in question, it still ended up sounding exactly the same as it did in iTunes... :( Below is the output upon completion. Any thoughts at all? --Kurt Shaped Box (talk) 23:15, 20 August 2012 (UTC)

Track 25

Filename F:\Downloads\25 Track25.wav

Suspicious position 0:02:20 Suspicious position 0:02:34 Suspicious position 0:02:47 Suspicious position 0:03:13 Suspicious position 0:03:33 Suspicious position 0:03:52 Suspicious position 0:04:05 Suspicious position 0:04:08 - 0:04:11 Suspicious position 0:04:13 - 0:04:18 Suspicious position 0:04:20 Suspicious position 0:04:22

Peak level 99.4 % Extraction speed 0.1 X    Track quality 94.6 % Copy CRC 9B604574 Copy finished

There were errors

End of status report


 * You could also run a CD cleaner in your DVD drive, just in case that's the problem. StuRat (talk) 22:35, 20 August 2012 (UTC)

The top is unscratched as well as the bottom? ¦ Reisio (talk) 00:21, 21 August 2012 (UTC)


 * (Reply to OP not Reisio.) You could try fooling around with the EAC settings to make sure they're set right, for starters it's always helpful to read the track twice to see if you're at least capable of replicating it. But from my experience it's not uncommon some discs with defects simply don't work on some drives while working fine on others. As Reisio said, are you sure the CD is fine on both sides? Talking about the reading side, and damage can be defective, sometimes a seriously looking scratch or a highly scratched surface can cause no problems while a single minor looking scratch can cause major problems. (Whether it's along the data track or across obviously makes a difference but from my experience it's more complicated then that.) The problem would be much more acute with audio CDs since they have very little error correction information. For a CD, since the reflective layer is on the top, you're pretty much SOL if it's damaged.
 * I note you say 'apparently' which suggests to me you don't know enough about the CD's history to know if it could easily have suffered minor damage. It's also possible there was a mastering or pressing error, I had this once with a CD-ROM made by shall I say a 'questionable source'. I bought 2 or 3 different copies from different stores in different places, all had the same error. I noticed there was visible defect on the CD although I don't know if this was the cause of the problem or it was something else (e.g. a mistake could have been made with the error correcting information or with the data such that there was an uncorrectable error on the disc, as is sometimes done intentionally for copy protection purposes).
 * Also how bad is the skip or glitch? If it's just a single glitch, then I wouldn't even read much in to the 'play through absolutely fine' bit. Audio CD players, since they are intended to read audio CDs and often don't do much buffering, they generally just interpolate (if they're decent players), if they encounter an error . This doesn't generally happen with digital audio extraction, and often doesn't even happen with playback on computers. This fact is relied upon by many audio CD copy protection systems, although I don't believe that's the problem here since you only have one or so error one a single track, but it does tell you why your audio CD may sounds fine on your player but not on your computer or when extracted. If you don't care about bit-perfect audio, for this single track you may want to look in to masking the error via interpolation the same way your audio player may be doing rather then trying to read the actual data.
 * Nil Einne (talk) 03:38, 22 August 2012 (UTC)