Wikipedia:Reference desk/Archives/Computing/2013 February 18

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February 18[edit]

Keyboard wiring[edit]

According to this (in the section labeled "The Keyboard's Connector"), four of the six pins on a PS/2 keyboard plug have functions. A fifth used to. So why was there ever a sixth? Thanks, Dismas|(talk) 11:25, 18 February 2013 (UTC)

Our article says Sometimes the port also allows one of the devices to be connected to the two normally unused pins in the connector to allow both to be connected at once through a special splitter cable. This is referenced to here, giving a table of the pin connections when used in such a way. - Cucumber Mike (talk) 15:17, 18 February 2013 (UTC)
Thank you! Dismas|(talk) 06:46, 20 February 2013 (UTC)

sql; any dummy tables?[edit]

not sure if dummy is the right word; but..

create table foo as select 1 as x;

doesn't work because it wants a from clause.

create table foo as select 1 as x from _null_;

doesn't work because _null_ doesn't have any columns. So is there some similar kind of preexisting dummy table defined in sql (hoping for something universal, not limited to any particular dialect) I can use for situations like this where I don't care about the table, I just need it to make the from clause happy? thanks. Gzuckier (talk) 14:37, 18 February 2013 (UTC)

any reason not to do something like CREATE TABLE newTableName (column1 int,column2 varchar(255)) --nonsense ferret 16:15, 18 February 2013 (UTC)
What exactly are you trying to do ? You're creating a new table, right ? What's the "Select 1 as X" supposed to do ? StuRat (talk) 16:21, 18 February 2013 (UTC)
You can (in MS SQL server, any) say SELECT 1 as x INTO foo to create the table 'foo' with column 'x' defined as an int. AndrewWTaylor (talk) 16:34, 18 February 2013 (UTC)
.. and in a stored procedure you can make it a temporary table (which is local to the SProc and disappears when it finishes) by prefixing the name with '#': SELECT 1 as x INTO #foo.AndrewWTaylor (talk) 16:41, 18 February 2013 (UTC)
Are you trying to do this (where x is another table)? create table foo as select * from x; Sandman30s (talk) 12:17, 21 February 2013 (UTC)

video file compression[edit]

I've been filming things for a hobby of mine and uploading them to the internet to share with other interested people. However, I recently got a new, more expensive camera, resulting in higher quality images, and larger file sizes. I have a selection of video files to upload now, ranging from 350MB to 1.3GB, and the site I want to post them on has a maximum file size of 500MB, so some of these are going to need to be reduced in size, but without too much damaging the image quality. I was recommended by a friend something called a H.264 encoder, which pretty much just reduced the file to random bright colours, though it was only 25MB, so that's something.

So, any other ideas of programs I could use to get these videos down to a size that I can upload properly? To make some of them less than half the original size isn't going to be easy, I'm sure... (talk) 20:52, 18 February 2013 (UTC)

Note that the web site needs to know how to uncompress them, too. Another option is to break them up into "chapters", each of which is small enough to upload. Or, you could reduce the frames per second, color depth, or resolution (what are your current settings ?). StuRat (talk) 21:03, 18 February 2013 (UTC)
yea, that's what I meant, just make the files themselves smaller, would have to reduce quality a little bit, but hoping for something not overly noticeable. currently 720p and I think 24fps, that's normal isn't it? I don't know all the technical details. (talk) 21:10, 18 February 2013 (UTC)
If this isn't normally going to play in full screen mode, you can probably get by with less than 720p, and people trying to stream 720p may find it lags. So, many web sites use less than that. Note that 360p wouldn't just be half the size, but 1/4th, which should be enough. Reducing much below 24fps would make it look jerky, though. Do you know the color depth ? (32 bit, 24 bit ?). StuRat (talk) 21:23, 18 February 2013 (UTC)
No idea of the colour depth, maybe I could check, but I suppose you're right about it playing on small screens and embedded in the website and such, it's not going to need to be really high resolution, is it. How do I change that, though? (talk) 21:28, 18 February 2013 (UTC)
What video editing software do you use ? If you just upload it directly from your camera to the website, then you may need to change the resolution on the camera before you record. StuRat (talk) 22:08, 18 February 2013 (UTC)
That's the thing, I don't have any decent video editing software, so I figure I would need to get some, so I can sort these files out (talk) 01:07, 19 February 2013 (UTC)
Are you looking for something free ? StuRat (talk) 01:26, 19 February 2013 (UTC) Easiest way to get (a decent copy of) FFmpeg on Windows is via ¦ Reisio (talk) 02:02, 19 February 2013 (UTC)
What Operating System are you using right now (Windows, Mac OSX, Linux?) and what format is your camera saving these files (and if you don't know that, which camera model is it?). Don't adjust the framerate... there are 2 primary framerates in use, NTSC and PAL... you don't adjust that, you adjust the encoding and the bitrate if you want to change the size. Shadowjams (talk) 04:33, 19 February 2013 (UTC)
And the dimensions, if it’s much over 720p and of fairly long duration. ¦ Reisio (talk) 05:43, 19 February 2013 (UTC)

FYI, many new expensive cameras have options to compress video on the camera. Some default to "uncompressed" or "very lightly compressed" on the premise that you want to control this parameter yourself in postprocessing. So, you may find that simply running the H.264 compression defaults (using FFMPEG, already recommended above), is all you need to do. Nimur (talk) 15:56, 19 February 2013 (UTC)

Free would be nice, as it's something I would only use maybe a dozen times, not worth spending lots of money on. Running Linux Mint at the moment, and the camera is a Panasonic Lumix, 720p and between five and ten minutes each. Trouble is, I've already filmed everything, so changing camera settings is going to be of no help any more, I need something to change the files already saved on my computer. (talk) 16:59, 19 February 2013 (UTC) with sudo apt-get install ffmpeg, then. ¦ Reisio (talk) 02:02, 19 February 2013 (UTC)