[wellylug] MPEG/DVD encoding/decoding.

[Jonathan Harker]

David Zanetti wrote:
> I honestly do wish people would stop living in the past and using MPEG-1
> etc and take advantage of the gain in space and quality with open but more
> recent codecs (eg, xvid, which works really well with the AVI container
> for decent quality content..)

I agree generally with your sentiment, but don't be fooled - the codecs you're 
thinking of may be open source, but they are most often NOT open free standards.

Examining the XviD licence shows that using XviD for anything other than an 
educational software engineering exercise is unlicensed use. XviD is an 
implementation of the MPEG4 compression scheme, and as such requires a paid 
licence to use for BOTH encoding AND playback. This is why Apple kicked up 
such a fuss when they were about to release Quicktime 6, since they had 
contributed the Quicktime file format to the MPEG committee for use in the 
MPEG4 scheme, and felt that playback should be available for free. I am not 
sure whether that part of the MPEG4 licencing was resolved or not.

Hardware assisted encoding aside, and since we're talking about being 100% 
legal, you cannot actually use any of the various MPEG2 or MPEG4 algorithms on 
Linux such as ffmpeg, divx, xvid, etc. for encoding video, which doesn't 
really leave much else you can do with them. :-) This is why with Mandrake, 
for instance (I can't speak for Debian), they are tucked away on the 
underground PLF archive and not included in the standard distro, even the 
commercial version.[*] The same goes for the AAC audio codec (used on the 
iPod), any of the various mp3 codecs for encoding (though playback is okay), 
AC3 (A52 or Dolby Digital) and so on. It seems that the only decent 
unencumbered video codec is the original MPEG 1. This crap state of affairs 
was why Xiph.org (home of Ogg Vorbis, flac, and others) was founded in the 
first place, to create good free (as in speech) media codecs.

AVI (Audio Video Interleave) is just a container format for interleaving audio 
and video streams independent of the compression codecs used. It's showing its 
age and needs replacing; Microsoft have developed their Advanced Streaming 
Format (.asf, .wmv, .wma, etc) and good open candidates are the Matroska 
format (.mkv) and the Ogg Media container (.ogm).

Hope that helps to clarify some things  :-)
Cheers,
J

[*] As an aside, perhaps Mandrake would be better to include an official DivX 
in the commercial version of the distro, instead of some of the other crap 
commercial apps they include.