Wikipedia:Reference desk/Archives/Computing/2006 August 4

media players and burners
ok, i have 2 questions, first is there a media burner that could burn different kinds of formats such as .mkv|.rmbv|.avi etc.? Cause i'm doing this project where i have to combine this 2 video, one is avi and the other is .mkv, and windvd creator 2 doesn't accept the .mkv one, any solutions for this?

Also, is there a media player that could play both files, so that you could group them into playlists... the only trouble for me is the .mkv ones or the matroska ones... thx in advance...


 * If memory serves, both .avi and .mkv are container formats, not video formats, so it should be relatively easy to convert one to another. It is said that virtualdubmod can perform this for you. Here is a random posting that seems to contain instructions in a sense of the word. But with a little toying around it shouldn't be hard... digfarenough (talk) 04:22, 4 August 2006 (UTC)


 * For playback, try Media Player Classic or VLC media player. They both have playlist and MKV support. - mako 08:00, 4 August 2006 (UTC)

xms
what is xms for mobile?


 * I think several providers use this abbreviation, usually to mean an extention or enhancement for the SMS system. An example is Xecure Message Service, an encrypted version of SMS. --Canley 06:27, 4 August 2006 (UTC)

Thanks canley.. are there any user reviews for this system?

music file !!!
music file !!! hi, i have a music file that is a "CLASS.File". i've got no clue what software to open it with. what programme can download of the net that is not a shareware or a trial. thanks - DAVE
 * did you try mplayer?Jon513 08:47, 4 August 2006 (UTC)
 * Yeah, it's been said that mplayer can play everything, and from my experience, it has. More details about the file in question would be helpful; if it is truly a *.class file, then what you have is compiled Java bytecode, not a music file. -- Daverocks (talk) 10:48, 4 August 2006 (UTC)


 * Yeah, you might not want to run it unless you are sure it is a music file. You didn't, per chance, download it from a Peer-to-peer service did you? There are many viruses on those places which people try to make look like music files, often by using lesser-known scripting extensions (like .vbs). --Fastfission 15:31, 4 August 2006 (UTC)
 * I was thinking that it a another type of media file that has accidently been renamed to .class If that is the case mplayer can still play it since it looks that the file header not the file extension. Jon513 15:41, 4 August 2006 (UTC)


 * Open it in a hex editor. If the first five bytes are CA FE BA BE 00, you have a Java bytecode file. Congratulations, Dave. You're screwed. --Optichan 17:12, 4 August 2006 (UTC)

SLA base pricing
Hello - I'm reviewing proposals for sourcing IT Infrastructure Services (Distributed Services, Help Desk, etc.). All potential providers used the cost model my company requested, but one stated that theirs is SLA based pricing. Can someone provide me with some background on this methodology and let me know what the trigger ponts are for negotiating? Thank you.


 * SLA = Service Level Agreement. SLA Pricing includes the equipment and people in an attempt to be all-encompassing.  It can be good, letting you know how much support will be.  It can be bad - telling you to go with the Windows server because the cost of service on a Redhat server will be a million times more. Youth in Asia 14:59, 4 August 2006 (UTC)

C# question
I'm writing a simple console application in c# which needs to handle very large numbers where every digit is signifigant. Does anyone know of a good arbitrary-precision class for c#. Efficiency is not an issue as I have lots of computing resources, but a very high (or none at all) overflow is critical. Thanks, 48v 17:53, 4 August 2006 (UTC)


 * Try looking at the BigInteger and BigDecimal classes. --Kainaw (talk) 17:56, 4 August 2006 (UTC)


 * Thank you very much. The second part of the question is this: Is it possible to index a List (System.generics) or an array with something larger than the 32-bit integer? 48v 18:06, 4 August 2006 (UTC)


 * It sure sounds like the data you're proposing to store is intrinsically sparse, so you probably want to use C#'s implementation of an associative array (a hashtable). You certainly don't want to be declaring a regular array with four billion members, never mind a bigger one yet. -- Finlay McWalter | Talk 22:51, 4 August 2006 (UTC)


 * Thanks. In fact, the 32 Bit integer in C# overflows around 2 billion, and yes, I'd like to have a list 5 or 10 billion elements long. Thus the difficulty. I can use an array if necessary, although using a list saves some complexity and code if it is possible to use a different indexer there. I do have non-default values for every entry; the data is not sparse, just a very large set. Thanks for the pointer to the associative array, I'm not clear on if that is still restricted to a 32 bit integer, but I will persue it further if a way to continue using the list or array functions does nto turn up soon. 48v 08:35, 5 August 2006 (UTC)


 * If your dataset truly is that size (wow), then any kind of in-memory storage is going to explode - even 2 billion entries (assuming a fairly conservative 16 bytes per object, including all the inevitable overhead placed on it by the allocator) would take 32 gigabytes of RAM/swap. Even in the event that the OS does let you allocate all that, performance is going to be soul destroyingly bad.  It's much better, surely, to use a smart storage manager, and if you just want "giant array" then you'll do no better than Berkeley DB, for which there is a dotNET wrapper.  It handles vast tables (up to 256 TB, they claim) and is very fast.  I can't speak for the programming paradigm they use for it on C#, but in python it's just the same as the associative array syntax - so once one has declared it, one can treat it as if its in memory, and the BDB engine takes care of swapping and caching (and in a much smarter way than the windows pager would do). -- Finlay McWalter | Talk 09:39, 5 August 2006 (UTC)


 * Thanks. I'll try that. I didn't realise that the memory was quite that extreem. (apparently it isn't linear because of how it's alloted/wrapped?) Thanks for the help and patience! 48v 15:51, 5 August 2006 (UTC)

Info from IP
How do you find a telephone number, street adress, or email adress from an IP. I can't find a whois that can tell me. Thanks *Max* 18:57, 4 August 2006 (UTC).


 * In general, you can't. IP addresses are often shared by many users. You can, however, find out who owns the block of IPs that the given IP is a part of, then attempt to contact the owner of that block (probably you can find something online to tell you, usually I just do a traceroute on the IP and see which network it ends up in). On a related note, for a registered domain name, that information for the person who owns the domain is usually available (e.g. through whois). Maybe someone else can provide better information... digfarenough (talk) 19:32, 4 August 2006 (UTC)

Fortunately for privacy, 99.9% of the stuff you see in movies is utter crap. --mboverload @ 06:20, 5 August 2006 (UTC)


 * Does this help? --Yanwen 18:59, 5 August 2006 (UTC)


 * You can't. --Proficient 04:24, 9 August 2006 (UTC)

Converter WMA..............
Hi, can you tell me any free software which can convert formats into WMA formats ???

Thank you --Sangeeth 21:36, 4 August 2006 (UTC)
 * You would be way better out redownloading the file. Converting from one format to another makes already crappy music files sound even worse. --mboverload @  06:24, 5 August 2006 (UTC)
 * Google for "WMA converter". Done. By the way, transcoding lossy files is evil.--Frenchman113 on wheels! 15:11, 5 August 2006 (UTC)


 * Windows media encoder is freeely downloadable from the microsoft web site. If you are going to transcode, it's a fairly good tool (assuming you're running windows.) 48v 15:45, 5 August 2006 (UTC)

Robots
I recently have become very intrested in robotics. My question is how I can get a robot to make decisions from video such as retrieving objects? I have heard of this done before in competitions where the robot retrieved cans and brought them back to a designated location.


 * It'll take quite a bit of work if you're starting from scratch. Let's try to make it as easy as possible. You don't want to actually use a hand or something like that to pick up objects, you're much better off with a magnet (an electromagnet if you want it to be able to drop things later). The arm the magnet is on should have very little freedom of movement, probably one degree of freedom is best (say, rotating in a vertical plane from straight ahead to angled down, touching the ground). Presumably this is a wheeled robot, because walking is pretty tough, so the robot will need to be able to move forward and backward and to rotate left or right. Finally, the vision. The simplest method is to have the target objects uniquely colored (e.g. cans painted red on a black floor). If you want to just preprogram things, you'd have the robot check its vision for a group of red pixels, rotating left or right to move the group into the center of its vision, then approaching until the magnet can pick up the object. If no group of red pixels are found, it should rotate in one direction until a group is seen (this assumes there are no barriers between the goal and the robot). The problem of deciding when the object is near enough to be picked up will be left to you. If you'd prefer the robot learns to do these things on its own, I'd suggest using an RL algorithm like Q-learning. The actions would be as above, and as for the states I'd suggest preprocessing the vision by dividing the visual field into vertical stripes and having the state be the number of red pixels in each stripe. There may be much simpler ways (I have a tendency to overcomplicate things), but, in general, robotics is a pretty complex thing, and vision even more so. Read lots, play around, and good luck! digfarenough (talk) 23:48, 4 August 2006 (UTC)


 * See computer vision. --cesarb 00:08, 5 August 2006 (UTC)

Awesome this helped alot Thanks.


 * Another method to control the motion of a robot is to have it follow a colored line on the ground. I've seen this used in automative assembly lines. StuRat 07:57, 5 August 2006 (UTC)