With so many versions of oggenc floating around, i thought of putting together a list of some of them.

encoder: aoTuV beta 2

vendor : AO; aoTuV b2 [20040420] (based on Xiph.Org's 1.0.1)

remarks: tuning done by aoyumi for all bitrates

aoyumi's encodersencoder: aoTuV pre beta 2

vendor : AO; aoTuV b2 test [20040402] (based on Xiph.Org's 1.0.1)

remarks: tuning done by aoyumi for all bitrates

aoyumi's encodersencoder: aoTuV pre beta 2 + QK 3.2

vendor : AO; aoTuV b2 test [20040402]+QKTune beta 3.2 (based on Xiph.Org's 1.0.1)

remarks: merge of tuning by aoyumi and Quantum Knot (w/o HFR)

Quantum Knot's encodersencoder: GT3b1

vendor : Xiph.Org/Sjeng.Org libVorbis I 20020717 (GTune 3, beta 1)

remarks: tunings by Garf for high bitrates (q >= 5), based on vorbis 1.0

Garf's encoderencoder: GT3b2

vendor : Xiph.Org/Sjeng.Org libVorbis I 20031230 (GTune 3 beta 2)

remarks: tunings by Garf for high bitrates (q >= 5), based on vorbis 1.0.1

GT3b2 Encoderencoder: GT3b2 + HFR

vendor : Xiph.Org/Sjeng.Org libVorbis I 20031230 (GTune 3 beta 2 with HF Reduction)

remarks: Garf's tuning merged with Quantum Knot's HFR

Quantum Knot's encodersencoder: QKTune beta 3.2

vendor : Xiph.Org libVorbis I 20031230 (QKTune beta 3.2) EXPERIMENTAL

remarks: tuning for pre echo and high freq reduction by Quantum Knot

Quantum Knot's encodersAs of now it is recomended to use GT3b2 for encoding with q >= 5

For q <= 4 it is recomended to use aoTuV beta 2

Let me know if i missed some encoder or information is incorrect / inaccurate.

[edit: links added]