Wikipedia:Reference desk/Archives/Computing/2013 July 21

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July 21[edit]

Converting from an ages-old Video-for-Windows codec to "modern" h264[edit]

Hi all,

my CCTV software (GeoVision) supplies me with AVI videos with the GMP4 codec ("Geovision MP4"). The codec is supplied as a Video for Windows 32-bit driver only, so I had to set up a virtual machine to even be able to play the files with MPC-HC. What software can I use to convert the files into something more universal like h.264?

The "usual suspects" ffmpeg/VLC don't play the file at all because they are not able to use VfW codecs.

84.153.7.232 (talk) 02:31, 21 July 2013 (UTC)

Before I suggest any solutions, I'd like to test them out myself to make sure they work. Can you upload a sample video clip to the Internet and link to it here? I will download it and see what works.—Best Dog Ever (talk) 08:51, 21 July 2013 (UTC)
I am sorry, I'm not allowed to disclose the videos (I work in a casino, it's not allowed for privacy reasons). I just need some way to watch them at home because somewhen in my shift some idiot stole quite a sum of money from me. 84.153.7.232 (talk) 09:23, 21 July 2013 (UTC)
I'm thinking to a way which must work. Can you watch it in fullscreen? 2A02:8422:1191:6E00:56E6:FCFF:FEDB:2BBA (talk) 09:56, 21 July 2013 (UTC)
Sure, but I'd rather like something not involving screencapping =) 84.153.7.232 (talk) 10:32, 21 July 2013 (UTC)
The GeoVision website has a download section with the codecs and/or MultiView software to view the files. Can you use those? --Canley (talk) 13:05, 21 July 2013 (UTC)
He/she probably can since he/she write he/she wanted to view the video at home.
Your codec look enough old to not have any way to convert it. Your casino is using old camera which have their own codec. It is not open source, so you don't know how the format work. I've seen a database with million of entries working with a DOS only program. Over decades, they still need DOS because they can't convert it.
You will waste your time if you try something endless. Instead of asking a way to convert an old codec, you should ask for a screen video capture software which don't need installation. I was asking if you can watch the video in fullscreen, it may be not necessary. I remember picpick which allow capturing the output of a windows. You should look for something similar which do video. 2A02:8422:1191:6E00:56E6:FCFF:FEDB:2BBA (talk) 13:36, 21 July 2013 (UTC)
Hypercam (here) and Camstudio (here) - I can contest to both of them. I've tried others but these two are my favourites. --Yellow1996 (talk) 18:06, 21 July 2013 (UTC)
You could try the "usual suspect" of the old days, VirtualDub. KarlLohmann (talk) 15:37, 21 July 2013 (UTC)
MeGUI (ignore the article, it's not about what MeGUI usually refers to but I don't think there's currently a better redirect target so I can't change it) [1] is generally my favourite for these sort of things but really the above answers seem to be complicating things way too much, there must be hundreds of tools capable of this sort of thing and it's likely a large percentage of transcodes on Windows use such tools (the idea that you can open play a file in MPC-HC but it's too 'old' to 'convert' is just strange). As mentioned by KarlLohmann, VirtualDub is another option although in that case you'll need to make sure you have a suitable encoding codecs installed yourself. Presuming you're correct and GeoVision really only provides a VfW codec, this may complicate matters slightly but probably not much since many tools are still built around it, it would be more concerning if only a DirectShow filter was provided, let a Media Foundation filter, as support for these generally remains poorer in such tools. I mean worse case scenario, many tools will have the fall back option of AviSynth or something similar frame serving (some of course use it by default). I would recommend a more specialised forum like Doom9 if you have further problems. Nil Einne (talk) 18:42, 21 July 2013 (UTC)
Just a thought here; Are casino employees allowed to take security videos home with them for their own purposes, and wouldn't that in itself breach the very privacy rules the OP mentioned earlier? Astronaut (talk) 18:57, 22 July 2013 (UTC)
It may still be better for him/her to find a way to find the thieve rather than explainning to his boss he/she has been stolen so much money. 2A02:8422:1191:6E00:56E6:FCFF:FEDB:2BBA (talk) 19:42, 22 July 2013 (UTC)

Broken jpg/jpeg image[edit]

Remember earlier in the internet when there were broken jpeg images, such as this: http://2.bp.blogspot.com/_Ze5Xm5fW-4o/TUnUBt6ADUI/AAAAAAAABJA/2WGSLTNK1K4/s200/broken-link-image-gif.jpg. Is there an official image of the broken jpeg that Joint Photographic Experts Group may have used? I can't see too much info, even on the Wiki page. Thanks! Baseballfan (talk) 04:26, 21 July 2013 (UTC)

The JPEG file format specification explains what a file needs to contain in order to be valid, but does not say anything about how invalid files should be handled (or how valid files should be handled, for that matter). Looie496 (talk) 04:35, 21 July 2013 (UTC)
The original "broken image" icon was designed by Marsh Chamberlin of Netscape Communications for the Netscape browser—it's a function of the browser UI, not part of the JPEG specification. --Canley (talk) 12:58, 21 July 2013 (UTC)

VPN security[edit]

I am planning on using a VPN, but little do I know about networking. Basically all my incoming and outgoing data is passed through an intermediate server, and theoretically that data can be compromised. But from what I've heard, HTTPS protocol can encrypt the data, prevent the data from being compromised by a third party. The owner of the server I connected to may keep track of websites I visit, but can him acquire my password or any important information? -- Livy (talk) —Preceding undated comment added 14:39, 21 July 2013 (UTC)

VPNs are used for many different things, I assume you want to use a VPN to provide some anonimity and safety, and not to securely connect to your company's network. In this case, it is not much different from using Wifi at the house of a far-away friend. His router, and all routers between him and the places you visit, can see your traffic just like your own ISP would if you didn't use a VPN - they just have a harder time telling where it originally came from. You're best of still taking all the security precautions you would (like using HTTPS) just as if you were at home, and you need to realize that there are many more ways to leak (parts of) your identity than just hiding the IP address you're connecting from. If it's anonimity you're looking for, you might want to look into Tor (anonymity network). But if you want to encrypt your traffic from curious eyes, using a VPN will probably only prevent the first few routers in your connection from seeing your traffic. Unilynx (talk) 17:19, 21 July 2013 (UTC)
If you are planning to use tor, the secrurity you think having will be only effective if your domain is availaible in .onion.
Update: OpenVPN and other work at the SSL layer. You probably want a IPsec solution. 2A02:8422:1191:6E00:56E6:FCFF:FEDB:2BBA (talk) —Preceding undated comment added 20:40, 21 July 2013 (UTC)

Linux toolbox: what should beginners learn[edit]

I am new to Linux, coming from Windows (obviously) and would like to assemble a basic toolbox.

I find emacs incredible, I am learning some bash syntax and Perl one-liners.

I'd like to learn more of these things that previous Windows users don't even know that exist, but would profit from learning.

Jean — Preceding unsigned comment added by 34and34 (talkcontribs) 16:50, 21 July 2013 (UTC)

A bit of a broad question, but here are some webpages that might assist you: [2], [3] and (probably best of all) [4]. --Yellow1996 (talk) 17:57, 21 July 2013 (UTC)
I recommend learning Python for scripting. It's a lot better than Bash or Perl for anything longer than a few lines. -- BenRG (talk) 00:00, 22 July 2013 (UTC)
The word "better" is fraught with peril, but Python is arguably a much cleaner design. Bobmath (talk) 15:56, 22 July 2013 (UTC)
I don't know if you've got the basics under your belt yet, but if not, I'd start with learning:
There are some days (not every day) when I think to myself, "Man, grep is so useful, I don't know how I could live without it."
And on the days when I don't think that, I think, "Man, diff is so useful, I don't know how I could live without it."
(Now, with that said, I concede that diff, grep, and pipes are as useful to me as they are because I still manage to work mostly with text files, such that I can continue to make use of the "everything's a file" tenet of the Unix philosophy. If you're a more modern user of computers than I am, dabbling in images and music and video and whatnot, the tools of choice may be different.) —Steve Summit (talk) 22:49, 22 July 2013 (UTC)
Based on the questions people regularly ask here, some useful tools (that solve real problems people often have) include Imagemagick, Sox, FFmpeg, PDFtk, and ghostscript. The man command is your friend and find is immensely useful. cron and its cousin at make automating stuff practical. tar is very useful, and wget and cURL are immensely handy.. I'm personally fond of dd, nc, hexdump and its inverse xxd, and dpkg-query. But in my experience the "big two" utilities that save me the most time are ssh and rsync; used together they're remarkable. -- Finlay McWalterTalk 23:55, 22 July 2013 (UTC)
In addition to all of the above, I'd like to mention LaTeX for essentially anything a typical Windows user would use Microsoft Word for. LibreOffice Writer is similar to Word if you really want that, but LaTeX is incredibly powerful and useful if you take the time to learn it. It's just much more flexible than WYSIWYG word processors, although admittedly, it has a bit of a learning curve. (Fun fact: you can even make presentations with LaTeX! It has slightly fewer features than MS Powerpoint, but you probably don't need those features anyway.) --Link (tcm) 22:23, 23 July 2013 (UTC)
Definitly sed and find ... -exec cmd {}\; are indispensable. I now use Python for most scripting, but for some things gawk is hard to beat. And then there is cut, sort, uniq and, of course, backquotes. And who could forget the mighty ed! --Stephan Schulz (talk) 16:45, 24 July 2013 (UTC)
To answer your question, it would really help to know what you want to use linux for. Just as a desktop replacement, for programming, for...? Some more things I like about linux: Command-line completion with "Tab". Also exists to some extent in windows, but who would use command line in windows? As for editors, that's a personal thing, but I'd suggest to also try vi or its derivatives (I use vim) to see whether you might like it. It will be more difficult to do anything at first than in Emacs, so don't be discouraged. It has some advantages though like small size, exists on virtually any linux/unix, ... bamse (talk) 01:34, 27 July 2013 (UTC)