What's the difference between MPEG streams?

Bushido Philosopher · Post by **Bushido Philosopher** » Fri Aug 02, 2002 4:05 pm

What is the difference between MPEG-1, -2 and -4?

Never really thought about it until now.....

And what about MPEG-3? did they just skip that or something?

jbone · Post by **jbone** » Fri Aug 02, 2002 4:09 pm

IIRC, MPEG-3 was planned for use in HDTV/et cetera, but it was discovered that MPEG-2 performed better than expected at the desired bitrates, so MPEG-3 was deemed unnecessary and scrapped.

I feel too lazy to try and talk about the others right now.

AbsoluteDestiny · Post by **AbsoluteDestiny** » Fri Aug 02, 2002 4:14 pm

They are just different developments made by the Motion Picture Experts Group.

MPEG 1 was the first video compression standard they established way back when and mpeg 2 followed in order to allow higher resolutions and bitrates, storing more data.

Mpeg 3 was developed for HDTVs but actually got comprised into the high levels of the mpeg2 standard

Mpeg 4 is a further stage of compression designed for very low bitrates and divx is an implementation of that

for more info see:

http://www.mpeg.org/MPEG/starting-points.html

Bushido Philosopher · Post by **Bushido Philosopher** » Fri Aug 02, 2002 4:18 pm

Say, while I'm at it, I might as well ask this question.

Is there any book out there you recommend about video and how it all works?

I'm eager to know as much as perhaps jbone or ErMaC, but then I can't just keep asking questions like this. so does anyone know a good book i can get into...or maybe perhaps a good internet resource?

Bushido Philosopher · Post by **Bushido Philosopher** » Fri Aug 02, 2002 4:20 pm

aw my bad, i forgot about ya AbsoluteDestiny.

jbone · Post by **jbone** » Fri Aug 02, 2002 6:22 pm

I learned about this stuff by reading ErMaC's guide, by experimenting on my own, and by searching Google/doom9.org/mpeg.org for more info whenever I found something I didn't understand.

My advice? Don't waste your money on books. Just search for what you want to know on the sites I've listed above, and cross-reference stuff between sites to make sure you're being fed correct info.

ErMaC · Post by **ErMaC** » Tue Aug 06, 2002 8:18 am

I have never taken a single class, read a single book, or payed any money otherwise except for internet access to learn all I did about video. Just read a lot. People often ask how I know stupid shit like why DV should've been in 4:2:2 colorspace at a higher bitrate. Well, I just read.

jbone · Post by **jbone** » Tue Aug 06, 2002 9:56 am

ErMaC wrote:People often ask how I know stupid shit like why DV should've been in 4:2:2 colorspace at a higher bitrate.

Why should've DV been in 4:2:2 colorspace at a higher bitrate?

ErMaC · Post by **ErMaC** » Tue Aug 06, 2002 11:57 pm

Because 4:1:1 colorspace is not sufficient for editing purposes. Repeated recompressions will cause serious artifacting and picture degredation. I know this first hand. The full DV source of Soul of an Angel is a good example. Too many of the things at the time I was making it were run through DV compression a few too many times. The easiest place to see this flaw is in the Reds. In various MPEG standards you can see problems with solid reds becoming blocky, well DV exibits similar artifacting which is very noticable after multiple recompressions, although instead of becoming blocky instead you can begin to see distortions in various macroblocks.

Implementing DV in 4:2:2 colorspace would alleviate most of this problem as the colordata would be accurate enough that recompression artifacting would not be nearly as noticable. Panasonic and JVC both have their own non-standard standards of DVCPro50 and Digital-S, respectively, that implement dual DV codecs running in parallel for a total of 50Mbit/sec that store 4:2:2 colordata. DVCPro50 is expensive though, especially for equipment. JVC's Digital-S format is very esoteric, but uses SVHS tapes as it's medium since they managed to modulate the 50Mbit/sec into a 19micron head width which is the same as a standard SVHS tape.

Aren't you glad you asked?