General codec, video standards questions...

[j3flight]

Below are a few questions that plague me when I read stuff on the internet. In certain posts, I can't determine whether someone is confused and used the wrong term, or I am confused and need to learn more. So, if someone (who knows for sure) could please answer these few below, I would be very grateful!

1) What is the difference between DivX and Xvid?
DivX and Xvid are just different "brands" of MPEG4 encoders/decoders right? They are not separate standards, correct?

2) When someone refers to DivX and Xvid, are they typically referring to MPEG2 and MPEG4 standards as a group, or only MPEG4?

3) MPEG4 != MPEG2...right?
MPEG4 does a better job of compression, but is not completely standardized yet. Yes/No?
MPEG2 is what DVDs are encoded with (and what my Hauppauge PVR250 generates.)

Ok, that's it for now. Please feel free to correct any of my assumptions above, I think this will help other people too!

Jason

[Spartan]

DIVX: DivX™ is a new format for digital video, much like MP3 is a format for digital music. DivX™ is the brand name of a patent-pending video compression technology created by DivXNetworks, Inc., (also known as Project Mayo). The DivX™ codec is based on the MPEG-4 compression standard. This codec is so advanced that it can reduce an MPEG-2 video (the same format used for DVD or Pay-Per-View) to ten percent of its original size. DivX.com.

XviD: XviD is an ISO MPEG-4 compliant video codec. It's not a product but an open source project which is developed and maintained by people around the world. XviD.org

MPEG2: An encoding standard designed as an extension of the MPEG-1 international standard for digital compression of audio and video signals. MPEG-1 was designed to code progressively scanned video at bit rates up to about 1.5 Mbit/s for applications such as CD-i. MPEG-2 is directed at broadcast formats at higher data rates; it provides increased support for efficiently coding interlaced video, supports a wide range of bit rates and provides for multichannel surround sound coding such as PCM, Dolby Digital, DTS and MPEG audio.

MPEG4: An ISO/IEC standard 14496 developed by the Moving Picture Experts Group (MPEG), the committee that also developed MPEG-1 and MPEG-2. These standards made interactive video on CD-ROM, DVD and Digital Television possible. MPEG-4 is the result of another international effort involving hundreds of researchers and engineers from all over the world. MPEG-4 was finalized in October 1998 and became an International Standard in 1999. The fully backward compatible extensions under the title of MPEG-4 Version 2 were frozen at the end of 1999, to acquire the formal International Standard Status early in 2000. Several extensions were added since and work on some specific work-items is still in progress.

MPEG-4 builds on the proven success of three fields:

Digital television
Interactive graphics applications (synthetic content)
Interactive multimedia (World Wide Web, distribution of and access to content)

(All of the above definitions were stolen from videohelp.com

DVD / Digital Satellite transmissions are basically MPEG2 if I am not mistaken.

[KingArgyle]

Also to add to that...XViD broke off from Divx when the later decided to go the closed source route.

[j3flight]

Wow, thanks for all the information, I have been to that site before, I guess I should have checked that out first!


Is it a safe to assume that any decoder capable of playing DivX/Xvid (MPEG4) is also capable of decoding MPEG2?

[HenkH]

Is it a safe to assume that any decoder capable of playing DivX/Xvid (MPEG4) is also capable of decoding MPEG2?

No, MPEG2 codecs typically comes with DVD-playing software (Microsoft is 'not allowed' to supply it in a standard Windows distribution), while MPEG-4 codes are typically downloaded.

[j3flight]

Is it a safe to assume that any decoder capable of playing DivX/Xvid (MPEG4) is also capable of decoding MPEG2?

The answer is NO. Downloaded and tried Xvid and Divx and neither one knew what to do with MPEG2 files.

Ok, so now that I understand the advantages and limitations of MPEG4, give me your opinions of MPEG2 codecs...

MPEG2 DirectShow filters (decoders) I know about:
- Intervideo (comes with Hauppauge PVR boards, uses blend deinterlacing, so film sources look jerky, no config options that I know of)
- libavcodec, libmpeg2 (Usually built into an app - these seem to work great - Media Player Classic uses libmpeg2 - but they're not available as DirectShow filters to my knowledge, only sources are available)
- Moonlight Elecard (seems to be ok, doesn't deinterlace film sources very well even if i change the options, leaves little square logo in top right - annoying)
- ffdshow (for mpeg2, it actually just uses libavcodec or libmpeg2. Lots of deinterlacing options, but none are as smooth as DScaler on film sources)
- DScaler5 (the one I prefer, deinterlaces film sources perfectly, very fluid video, but zero configuration options)

So, does anyone have any opinion of the ones listed above?
Can anyone suggest any that I should try out??

Jason

[j3flight]

No, MPEG2 codecs typically comes with DVD-playing software (Microsoft is 'not allowed' to supply it in a standard Windows distribution), while MPEG-4 codes are typically downloaded.

Thanks for the info, you beat me to the post, but I hadn't come back to read the board before I submitted. =)

[KingArgyle]

DScaler 5 is still beta and under development, with that being said, you can configure it if you use a player that provides you access to the configuration utility, such as Zoomplayer. The nice thing about DScaler 5 is that it is 100% open source and free. The author has no intention of charging for it in the future.

DScaler 5 does a good job with film, but at least the version I tried had some interlacing problems with TV broadcasts. Films are already deinterlaced.

[j3flight]

DScaler 5 is still beta and under development, with that being said, you can configure it if you use a player that provides you access to the configuration utility, such as Zoomplayer. The nice thing about DScaler 5 is that it is 100% open source and free. The author has no intention of charging for it in the future.

Films are already deinterlaced.

Ooh, I'll have to try out ZoomPlayer then, didn't know that!

I think I have to disagree with you about films being already deinterlaced. If film sources are broadcast over the airwaves (or cable or satellite) they are interlaced. DVD video is also interlaced (for the most part).

Anytime you interlace film sources, it has to be telecined (take 24 frames per second and generate 60 fields per second) and it's this uneven number that gives software deinterlacers a hard time.

Jason

EDIT: All this telecine, 3:2 pulldown, etc, B.S. only applies to those of us with NTSC. Anyone using PAL has a much simpler job of deinterlacing because the ratio is just 2:1.

[j3flight]

Information for anyone interested in 3:2 pulldown (inverse telecine).
http://www.inwards.com/~dbb/interlace_myths.html

Another one...
http://www.divx.com/support/guides/guide.php?gid=10

There is one statement on that page that confuses me and I just read it:
"DVDs offer a strange twist to the whole telecine and 3:2 pulldown business. Almost all DVDs will have the movie stored as whole pictures at 24 fps. This is the original format of the film with no telecine."

I have read many articles that say exactly the opposite. KingArgyle, looks like we have conflicting sources! =) I'll do some more reading, cause now I'm interested.
Jason