[theora] Updated Vorbis & Theora plugins available for Helix & RealPlayer 10

Maik Merten maikmerten at gmx.net
Sat May 15 05:47:12 PDT 2004

John Kintree wrote:
> Is there someplace where people can download sample video files that are in 
> Theora format?

AFAIK there is no such place yet. (keep in mind the bitstream is not yet 
officially frozen)

> I've seen the trailer for Harry Potter and the Prisoner of 
> Azkaban in both RealPlayer 10 and VP6 formats.  It looks pretty good with 
> both of them at between 450 and 500 kbps.  For comparison purposes, it would 
> be nice to see the same trailer in Theora format.

For a fair comparison you need a high quality version of that trailer - 
transcoding something like "high quality" MPEG4 to Theora will very 
likely produce undesired additional artifacts.

Some time ago I did some comparisons using VQEQ test sequences from 
media.xiph.org. My personal conclusions: Theora tends to blur the image 
when running out of bitrate while MPEG4 (I tested XviD) tends to produce 
blocky artifacts. I do prefer blurring - but that´s only my personal 
taste. However, it´s important to keep in mind that current 
libtheora-encoder is still very VP3´esque and doesn´t use any of the new 
format features introduced with alpha3 AFAIK.

There´s a new, experimental implementation (written from scratch) 
available at


which implements those new features and will very likely produce 
superiour results once it´s ready. (At the time being the encoder is 
broken, "producing pretty horrible quality files with high bitrates")


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