Vorbis: Difference between revisions
No edit summary |
|||
| Line 22: | Line 22: | ||
* Quality at high bitrates could benefit from further tuning | * Quality at high bitrates could benefit from further tuning | ||
= | =Techniques used in compression= | ||
* Advanced psymodel | * Advanced psymodel | ||
* Coupled stereo modes ( | * Coupled stereo modes (Point/Phase Stereo and [[lossless]]) | ||
* [[Huffman coding]] | * [[Huffman coding]] | ||
* Vector quantization | * Vector quantization | ||
* Modified discrete cosine transform ([[MDCT]]) | * Modified discrete cosine transform ([[MDCT]]) | ||
* Multiple block sizes for | * Multiple block sizes for window switching | ||
=Software= | =Software= | ||
Revision as of 00:08, 14 April 2005
Introduction
Ogg Vorbis (www.vorbis.com) is a fully open, non-proprietary, patent-free (subject to speculation), and royalty-free, general-purpose compressed audio format for mid to high quality (8khz-48.0kHz, 16+ bit, polyphonic) audio and music at fixed and variable bitrates from 16 to >256 kbps/channel. This places vorbis in the same competitive class as audio representations such as mpeg-4 (AAC), and similar to, but higher performance MP3, twinvq (VQF), WMA and PAC.
Vorbis is the first of a planned family of Ogg multimedia coding formats being developed as part of Xiph.org's ogg multimedia project.
Informal listening test suggest Vorbis to be comparable to mpeg-4 AAC at most bitrates and MPC at 128kbs. Transparency is generally reached at about 150-170kbps (with some exceptions). The encoder is reasonably young and unoptimized, so further improvements can be expected.
Unfortunately, Xiph.org has failed to improve Vorbis at a steady rate since its initial 1.0 release in July 2002. Since then development has been lead by other coders such as Garf and Aoyumi. Aoyumi's AoTuV series of encoders was incorporated into the September 2004 release of 1.1, which brought about the first quality improvements across the board for 2 years.
Pros
- Free (as in speech), Open Source and claimed to be patent free
- Good all-round performance (>48kbs - a leading codec at 128kbs)
- Well written specs
- Several portable hardware players
- Suitable for internet-streaming (via Icecast)
- Fully gapless playback
Cons
- Limited official development
- Current implementations are more computationally intensive to encode and decode than MP3
- Quality at high bitrates could benefit from further tuning
Techniques used in compression
- Advanced psymodel
- Coupled stereo modes (Point/Phase Stereo and lossless)
- Huffman coding
- Vector quantization
- Modified discrete cosine transform (MDCT)
- Multiple block sizes for window switching
Software
Encoders
Decoders
- QuickTime Component (Allows playback in QuickTime/iTunes)
- CoreVorbis (DirectShow)
- illiminable Ogg Directshow Filters (Also plays Speex, Theora and FLAC)
Hardware
The following list contains some players that support Vorbis playback.