Downloading

[swicks]

Can you tell me what do I look for when downloading files as far as how fast it will come in.

Also, what would determines the quality of video files?

[Quantum]

I've edited your post a little, I hope you don't mind. I want to first mention we don't condone in anyway copyright infringement.

Downloading speed is determined by a number of variables. The first thing you want to do is make sure the ports in your router or firewall are open that the P2P client uses, there will be many guides on how to do this on the P2P clients website. Also, and most importantly, the number of seeds and how fast they can upload. You often find on private torrent sites, because it's in the benefit of the seeders to seed, you can much faster downloading speeds for files that you want.

As for the quality of the video file, it is determined again by a number of variables, the key ones being: bit rate, codec and resolution.

The typical American resolution size is 640 by 480 for a 4:3 file and 720 x 480 for a 16:9 file (T.V widescreen). PAL television on the other hand, always works at the resolution of 720 x 576 and is stretched to the appropriate aspect ratio. These are the resolutions you find typical files in.

Bitrate determines the quality for a particular codec, the higher the bitrate, usually the higher the quality. However the type of codec is more important than the bitrate if there's only a spall difference, in order of popular codecs here is the quality from bottom to top:

mpeg2 < divx < xvid < vc-1 < h264

vc-1 is also known as wmv-hd, it's part of the wmv profile, but significantly better quality than the old wmv codecs. So for example, a 350mb 45min h264 file, if encoded properly, will look tonnes better than a 350mb 45min mpeg2 file.

When practically finding stuff, the mainly level of qualitys are often determined by resolution. So a standard file will be 350mb xvid 45 mins, you then get high resolution files often tacked with HR on the end, these are scaled down HD files, they're slightly higher quality and slightly higher resolution at 650 - 700mb xvid 45 mins. Then you get high definition files, the first lot is 720p, which is a resolution of 1280 x 720, these files are almost always encoded in h264 and you need a new CPU to play them (AMD64 line ore Core2 line are all very likely to play them with the right Codec, CoreAVC is the best CPU saving device for h264 files). A typical 720p file is either 1.1GB or 1.44GB for 45 mins. 1080p and 1080i aren't quite as popular yet, but you can get hold of them and they are a resolution of 1920 x 1080.

[Synbios]

Also to add to what Quantum said, the difference between 1080i and 1080p is practically negligable on PCs.

From my understanding, computers can only truly output progressive material. My CRT TV can only display 720p or 1080i, but if I download a "1080p" movie, it still shows up fine on my TV. The resolution is all that matters.

The only catch is that when my TV is set to 1920x1080, the refresh rate is 30Hz. Since it's interlaced, the TV  can only handle half the normal refresh rate. When I set the TV to 720, it runs at full 60Hz. For PC games, that might be a big deal. However for movies, most movies run at 24 FPS anyways, so running at 30Hz is fine.

[Quantum]

Also to add to what Quantum said, the difference between 1080i and 1080p is practically negligable on PCs.

From my understanding, computers can only truly output progressive material. My CRT TV can only display 720p or 1080i, but if I download a "1080p" movie, it still shows up fine on my TV. The resolution is all that matters.

The only catch is that when my TV is set to 1920x1080, the refresh rate is 30Hz. Since it's interlaced, the TV  can only handle half the normal refresh rate. When I set the TV to 720, it runs at full 60Hz. For PC games, that might be a big deal. However for movies, most movies run at 24 FPS anyways, so running at 30Hz is fine.

:/, I'd disagree with resolution being the only thing that matters. Simply put, per frame 1080i only put out 540 lines of information, where as 720p obviously outputs 720 lines, so certainly during fast moving sequences 720p holds an advantage, but for slow moving stuff 1080i does actually output more information per frame so can be higher quality. As for computers outputting, yes they output progressively, but unless you set your program to deinterlace the file (which can some times make it look better depending on the type of show and the deinterlacing algorithm) it will still just output interlaced as a subset of a progressive manner (i.e every line will be updated, but only every other line will be updated with 'new' information).

This is at the moment somewhat a moot point, as almost all 1080p and 720p T.V shows that are encoded are taken from 1080i source, the source will be the best quality but will often be 3 - 4GBs for 45min shows, so upto you if you have the hard drive space. But is fairly important when you downscale or re-encode Blu-Ray or HD DVD sources.

As for refresh rates, the ideal refresh rate is 120 Hz, this fits nicely as 24 x 5, 30 x 4 and 60 x 2 (old PAL stuff be damned). When you're playing a film in 30 or 60Hz there is a certain amount of pulldown, which can lead to a slight jerkiness during scenes. I much prefer the way PAL deals which this, as it is 50Hz, is simply doubles every frame to get 24 to 48fps then increases the speed of the movie and sound by 4% to get to 50fps. Audio quality takes the very slightest loss as everything is pitched 4% higher, but very very few people can tell the difference.

[Synbios]

That's a very interesting point about PAL and how it increases the pitch of sound. I never heard of that, then again I have never seen a show/film in PAL. Everything I get is NTSC, as most pirated things I find are from the US or Canada...