Published Date 12/25/09 11:28 AM
It was correctly mentioned by visitors of the site that Ogg Vorbis encoders at SE are a bit outdated now. The more so as there were some developments in this field during 2008-2009. Vorbis encoder became an audio part of Theora – free and open format for multimedia exchange on the internet. Xiph.org foundation which passionately favors the spreading of this open source format, released their version of the encoder – libvorbis 1.2.3. It is used now for encoding in VLC player, RealProducer, multiple command-line utilities and applications for all operating systems. It is a part of Theora package. The same time thanks to Aoyumi who contributed a lot to make this codec sounding better, we have the latest and the most tuned version of the encoder – aoTuVb5.7. Probably all the enhancements made by Aoyumi will be integrated into Xiph's “official” version in some future, but for now the two major versions coexist peacefully along with four or five less widely used ones.
In order to find out how the “official” Xiph version compares to other non-Vorbis encoders and to see how far the latest development by Aoyumi goes, we decided to include them both:
- libVorbis 1.2.3 and
For making this comparison fair a small research was conducted. Below are bit rates of the above encoders depending on -q parameter which sets quality level of encoder output. Nine SE samples are used.
Vorbis bit rates depending on "-q" parameter in high resolution (PDF:306kb).
It's clearly seen that the curve consists of several separate monotonous segments indicating stepwise changes in psy-models of the encoders. And their comparison would be more informative for both developers and general public if it is within the bounds of corresponding psy-segments. So the first contenders for SE testing were chosen:
- aoTuVb5.7 -q1
- libVorbis 1.2.3 -q1.75
They use the same psy-model segment and result in the same target bit rate – 80.4 kbit/s. This quality setting (-q1) could be recommended for streaming purposes. And it perfectly fits SE 80 kbit/s group .
Also all Vorbis entries in SE ratings were renamed according to Xiph example – OGG used for media container and VORBIS – for audio codec.
As usually we thank people who suggested the codec for inclusion - Norz, Morten Wendelboe, Francis Chabot.
Don't forget to take part in testing!