Wikipedia:Reference desk/Archives/Computing/2015 February 20

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February 20

Strong signal but sporadic connection

I just moved to a new place and wifi is included in the rent. At my old place, I had a fairly weak signal but was able to get and remain connected. Currently, however, I have a very strong signal but am having connection problems. About 70% of the time when I go on the net, I get the error "Page can't be displayed. Check connection . . ." or whatever it specifically says. There are two other computer users who have had the same problem but to a much smaller degree. The owner has rebooted the modem or DSL or whatever it is and has called the ISP. Apparently, things are OK from the ISP's perspective. I have scanned my computer several times (including updates, etc.) and there is nothing showing up as a problem. Anyone have any ideas why I am receiving such a strong signal but can't load pages? 50.101.125.154 (talk) 04:29, 20 February 2015 (UTC)

Interference comes to mind. I'm not sure how you would check for that, though, without special equipment. The usual solution to interference (assuming you can't eliminate the source) would be a directional antenna. If you don't know where to aim it, you'd just have to experiment (trial and error). StuRat (talk) 06:06, 20 February 2015 (UTC)

Another possible option, if you can find a location where there is not much interference (perhaps near to the router or away from other equipment), is to re-transmit the wireless signal with a wireless repeater (£20 in the UK). Dbfirs 15:43, 20 February 2015 (UTC)

Extract every frame from a video

How do I take a video and extract every frame from the video into png format? I want to save every single frame from a video and still have it all be in the same quality as the original videos quality. I already have Sony Vegas pro on my computer if that is a program I can do this in? I looked around for a while and couldnt find anything. — Preceding unsigned comment added by 204.42.31.250 (talk) 15:55, 20 February 2015 (UTC)

I use Linux - and we have "mplayer" (and it's sister program "mencoder") - a video player with a bazillion options - one of which is to split the video into individual frames and write them out in any reasonable format (png, jpg, etc). Mencoder can then reverse the operation. I have no idea whether that tool can be built for Windows (if that's what you're using) - but if it can, then it's a command-line tool. Our article lists some graphical front-ends for mplayer - but it doesn't look like any of them are Windows-capable, although I could be wrong about that. SteveBaker (talk) 16:46, 20 February 2015 (UTC)

I would worry that the frames might be less compressed than the video, resulting in a huge total file space. What kind of ratio do you see between the size of the movie and the individual frames ? StuRat (talk) 17:14, 20 February 2015 (UTC)

There is absolutely no doubt that the individual files will consume vastly more space than the video. VASTLY more. Even if you used a lossy format like JPEG. The deal is that videos use a form of data compression where they only store the differences from one frame to the next. To explains this somewhat simplistically: If you put your camera on a tripod and film your cat walking across the room, there will be one frame of video with the entire room in it, then a bunch of frames containing just the cat. When you convert the video into still frames, each frame has to contain a picture of the entire room...so obviously, the individual files *MUST* consume way, way more space than the original video. The precise ratio depends on how compressed the video was, the content, the resolution and a whole bunch of other unknowns - but I've seen videos get 100 times bigger when converted to still frames. SteveBaker (talk) 02:09, 22 February 2015 (UTC)

I think it would have been faster to type "mplayer windows" into Google than to type "I have no idea whether that tool can be built for Windows" into Wikipedia. The official site lists Windows builds here; there are ridiculously many of them, but the first site on the list is probably fine.

The command line to extract every frame to PNG (on any platform) is mplayer -vo png:z=# videoname.mp4 where # is a compression level from 0 to 9 (0 is fastest, 9 is smallest). They'll be named 00000001.png, 00000002.png, etc. in the current directory. The default seems to be z=0 so you could just write -vo png in that case.

I don't know whether any of the graphical frontends to mplayer support this functionality. -- BenRG (talk) 20:26, 20 February 2015 (UTC)