PDA

View Full Version : AVI vs DVD


hopenhower
2006-01-09, 10:36 PM
I'm sort of new hear, so don't hate me when you read this. I know how sensitive the trader community is to sound quality and is anti-lossy (for good reason), but I never realized this applied to video as well. I'm assuming a lot of these dvd's (GD in particular) are coming from VHS. Wouldn't it be easier to make them AVI's instead of DVD's? Not just easier, but the same quality, smaller, and a lot quicker to download/upload. I think the sound quality could be the same. If you wanted to make it into a DVD you could author it yourself, or if you have a decent DVD player, you could just burn the AVI's as data files and play them on your TV. When you input the video to the computer, it probably comes in as a huge AVI file, then you are transcoding it to a DVD video format, which is going to be lossy anyway, as far as the video goes. To keep it the same quality as the original VHS, it would be a matter of having a 1 gig torrent versus a 9 gig. Don't get me wrong though, I'm not complaining, just curious. I never new this stuff was even available until a week ago.

yeltzin_4
2006-01-10, 03:15 AM
Well DV-AVI (video that comes from a miniDVD/digital 8 video camera) video takes up about 13 Gigabytes of space per hour, which is prohibitative for most people to download and store. That's why we convert to MPEG2 and store the resulting footage onto a DVD.
If you encode your footage correctly, use a decent encoder (CCE, ProCoder, TMPGEnc) and encode the footage at a high enough bitrate, it will be difficult to tell the difference between the original DV-AVI and the resulting MPG2 file.
You can fit 1 hour of video onto a DVD5 (single layer DVD) at the maximum bitrate. Obviously you can put more video onto the disc but it will result in a reduction of quality.

The MPG2 codec is quite old (nearly 10 years old) and isn't very efficient. There are better codecs now available such as XviD and H.264 that outperform MPEG2 at the same bitrate. The reason why these codecs aren't as popular as MPEG2 is because the hardware to play these file formats isn't as readily available. Although with media centres, modded xboxes and computers networked to your television becoming the norm, people won't be forced to always use MPEG2 to distribute their videos.

brimstone
2006-01-10, 01:31 PM
I think most people that download video here would like to watch it on their tv and then DVD is the way to go. Although using DivX/Xvid (avi is a container format but i guess this is what you are talking about) would result in smaller files many people then would have to transcode to mpeg2 which would be an unnecessary loss of quality. There is also the risk that those copies would come in circulation as "real" DVDs which would degrade the trade pool.

hopenhower
2006-01-11, 11:12 PM
yeltzin_4, I was talking about the older VHS tape sources, not DV sources. With a 2 hr VHS being turned into a two layer DVD, you are making the file much larger than it has to be to have the same video quality. I would guess that a 1 gig XVID would have the same quality as an entire VHS tape. The hardware to play XVID's is readily available with the newer dvd players. They're only $125 or so. If anyone spends a lot of time transcoding, I suggest they get one and you will never have to spend hours transcoding again. You will also save in blank DVD media since you can get a lot more on a DVD (I would guess about 8 VHS tapes on a dual layer DVD without losing quality).
brimstone, if someone didn't have one of the DVD players that can play computer video files and they did need to transcode it, it wouldn't be an uneccesary loss in quality. When you download it as a video DVD, it already has been transcoded, and thus the loss is already there. As far as individually authored DVD's coming into circulation that are sub-quality, that problem is always going to be there, just like someone changing audio files to mp3s.
It just seems like it would be much faster downloading and uploading without much loss. It would also have a lot of benefits for DV sourced videos as well.

yeltzin_4
2006-01-12, 02:35 AM
yeltzin_4, I was talking about the older VHS tape sources, not DV sources. With a 2 hr VHS being turned into a two layer DVD, you are making the file much larger than it has to be to have the same video quality. I would guess that a 1 gig XVID would have the same quality as an entire VHS tape.

Extrapolating the figures used in your example above you seem to be suggesting that a 1400kbit/sec XviD file has the same quality as an 9800kbit/sec MPEG2 file. While XviD compression is much more efficient than MPEG2 I'd be sceptical that the XviD video would match the quality of the MPEG2 video. Though, it would be interesting to compare the differences. :)

My pet peeve is people who try to cram as much video onto a DVD5 as they can. It totally defeats the purpose of migrating your video from VHS/miniDV onto a DVD if the resulting video is blocky and full of compression artifacts. I've traded for 'upgrades' of concerts on DVD that look significantly worse than my VHS copies. It's a shame really.

I guess it comes down to standards. That's why DVD is so popular. People producing DVDs know that their video will be playable in all DVD players. My hope is that media centres become popular and the DVD/Blue-Ray/HD-DVD simply becomes a place of storage rather than tied to a particular video codec.

Malth
2006-01-12, 06:04 PM
Extrapolating the figures used in your example above you seem to be suggesting that a 1400kbit/sec XviD file has the same quality as an 9800kbit/sec MPEG2 file. While XviD compression is much more efficient than MPEG2 I'd be sceptical that the XviD video would match the quality of the MPEG2 video. Though, it would be interesting to compare the differences. :)



I think what he is saying is, you can have as high a bitrate as you want, but for something like a VHS sourced video, more bitrate becomes a moot point, because the original quality just isnt good enough to warrant it.

Its like that Nirvana Uncut DVD that for some reason was put onto 2 DVD's, the source video wasn't *that* good, and it could easily have been put onto 1 DVD and looked *exactly* the same.

livedead13
2006-01-12, 07:42 PM
[QUOTE=Malth]I think what he is saying is, you can have as high a bitrate as you want, but for something like a VHS sourced video, more bitrate becomes a moot point, because the original quality just isnt good enough to warrant it.
QUOTE]
I understand using this logic for the sake of saving bandwidth...

but the other logic would be that yes, the vhs source material doesn't look great because it's from tape, but is it really necessary to make it look even worse with digital compression artifacts, simply for the sake of an easier upload/download?

I would guess that the folks who spend hours and days capturing, syncing, and authoring these dvds are not concerned with small file sizes becuase a). they are concerned about getting the most absolute quality from their hard work, and b). they don't need to download them.

Malth
2006-01-12, 07:52 PM
Im not saying compress the hell out of it and make it look crappy, Im saying that some of this bitrate simply is not justified. If you can take a video and digitize with no loss in quality at say 300k/s, why would you need to jack that number up to 1900k/s?

Like I said, a prime example is the Nirvana Uncut DVD, the bitrate is simply way too high, and is not justified in any way shape or form. Im not advocating lowering a bitrate for the sake of lowering, Im advoicating choosing a realitic bitrate that properly reflects the source materials needs

Five
2006-01-12, 08:30 PM
I understand using this logic for the sake of saving bandwidth...

but the other logic would be that yes, the vhs source material doesn't look great because it's from tape, but is it really necessary to make it look even worse with digital compression artifacts, simply for the sake of an easier upload/download?

I would guess that the folks who spend hours and days capturing, syncing, and authoring these dvds are not concerned with small file sizes becuase a). they are concerned about getting the most absolute quality from their hard work, and b). they don't need to download them.
I couldn't have said it better myself :clap: :clap: