aoTuV beta6.03 (2020) technical information This version is based on Xiph.org's libvorbis 1.3.7. The part related to sound quality is not changed from previous version. 2021/03/20 Aoyumi ---------------------------------------------------------------------------- aoTuV beta6.03 (2018) technical information This version is based on Xiph.org's libvorbis 1.3.6. The part related to sound quality is not changed from previous version. 2018/04/18 Aoyumi ---------------------------------------------------------------------------- aoTuV beta6.03 (2015) technical information This version is based on Xiph.org's libvorbis 1.3.5. The part related to sound quality is not changed from previous version. 2014/08/08 Aoyumi ---------------------------------------------------------------------------- aoTuV beta6.03 (2014) technical information This version is based on Xiph.org's libvorbis 1.3.4. The part related to sound quality is not changed from previous version. 2014/04/29 Aoyumi ---------------------------------------------------------------------------- aoTuV beta6.03 technical information The differences from the aoTuV beta 6.02... 1. Fixed some causes that 5.1 channel coupling didn't work normally. And tuning of lossy coupling is included in it. 2011/04/24 Aoyumi ---------------------------------------------------------------------------- aoTuV beta6.02 technical information The differences from the aoTuV beta 6.01... 1. When a change of the volume is very big, that a bit allotment became superabundant was revised. It caused overflow. [M3] 2011/02/27 Aoyumi ---------------------------------------------------------------------------- aoTuV beta6.01 technical information The differences from the aoTuV beta 6... 1. When short blocks continued, that a bit allotment became superabundant was revised. It caused overflow in the extreme case. [M3] 2011/02/23 Aoyumi ---------------------------------------------------------------------------- aoTuV beta6 technical information The differences from the aoTuV beta 5.7... 1. "libvorbis 1.3.2" was merged. 2. A lot of bits are assigned in the part which strong post-echo produce. [New M2] 3. The search range of envelope is expanded. As a result, pre-echo by the specific pattern was improved. [envelope.c] 4. In the case that the strong tone and impulse ingredient coexisted, a bit allotment to the tone ingredient was improved. [M7] 5. The calculation method of dynamic thresholds of the stereo mode was changed. This is more effective than former method. [New M6 & M9] 6. The quantity of noise normalization is gained by a property of frequency signal domain. This reduces ringing by zero energy. [M8] 7. M4 was revised. As for this change, more correct audio energy control is formed in the low bitrate. [M4] In addition, some small revisions and tune up parameters are included. 2011/02/21 Aoyumi ---------------------------------------------------------------------------- aoTuV beta5.7 technical information The differences from the aoTuV beta 5.61... 1. Fixed the problem of floating point exception. (from xiph.org's libvorbis) 2. "libvorbis SVN-Revision 15533" was merged. Some revisions are included in it. 3. The process of the frequency band without the need is omitted now. And the case that speed becomes fast occurs. This change doesn't influence the encoding result. 4. Fixed the problem of a memory access violation. (beta5-M6 afterward) 2009/03/03 Aoyumi ---------------------------------------------------------------------------- aoTuV beta5.61 technical information The differences from the aoTuV beta 5.6... 1. Fixed the problem of floating point exception. (beta5.5-M3 afterward) 2008/12/15 Aoyumi ---------------------------------------------------------------------------- aoTuV beta5.6 technical information The differences from the aoTuV beta 5.5... 1. "libvorbis SVN-Revision 15530" was merged. The revisions of the security problem are included in it. Therefore this update is important. 2. The pre-amplitude processing was added newly. This is the function to adjustment the volume of sources beforehand.@All the initial values are set now. 3. The part of M3 code was fixed. This is bugfix of the beta5.5. ...and I tune up a few parameters. 2008/12/09 Aoyumi ---------------------------------------------------------------------------- aoTuV beta5.5 technical information The differences from the aoTuV beta 5... 1. The frequency domain width of M6 was revised. 2. For q-1/-2, a pre-echo reduction code was applied (M3). In addition, the M3 code was improved. 3. The floor setup parameters in the low bit-rate were changed. 4. The part including bug of noise normalization was rewritten. 5. "libvorbis 1.2.0" was merged. Furthermore, the revisions of Bug #300 and #1229 were applied. 6. The ATH curve of the high frequency area (more than 32kHz) was revised. ...and I tune up many parameters. 2008/03/30 Aoyumi ---------------------------------------------------------------------------- aoTuV beta5 technical information The differences from the aoTuV beta 4.51... 1. In order to work noise normalization correctly, the value of tone masking is compressed under certain conditions. A floor curve approaches the original audio spectrum line as a result. [New M4] 2. In order to cut down the bitrate, a part of M2 code of beta4 was deleted. @3. The ATH curve was changed slightly. 4. Pre-echo decreased slightly. This is based on change of M3 code. 5. In order to decrease artifact by collapse of audio energy, noise normalization processing of point stereo was extended. [32/44.1/48kHz only] 6. The threshold of channel coupling (lossless <=> point) is changed dynamically. This is a method based on a certain idea. [M6] ...and I tune up many parameters. 2006/10/24 Aoyumi ---------------------------------------------------------------------------- aoTuV beta4.51 technical information The differences from the aoTuV beta 4.5... 1. The changed part of "scale.h" of Xiph.Org SVN was reflected in aoTuV. This will solve the problem of the compile by gcc4. 2. A part of portion added by beta4.5 had caused memory access violation. Depending on environment, a problem arises in qualiy-1/-2. This problem was corrected. 2005/11/17 Aoyumi ---------------------------------------------------------------------------- aoTuV beta4.5 technical information The differences from the aoTuV beta 4... 1. M4 code of beta3 was deleted. M5 is added as what is replaced with it. The advantage of this method is that the result stabilized more is obtained. Instead, the change width of the bit rate becomes large rather than before. [32/44.1/48kHz only] 2. New M4 was added. There is this for the same purpose as M1. However, it is tuned up only in the low bit rate region according to work and individual parameters. [32/44.1/48kHz only] 3. M2 code was extended. This decreases a specific noise problem. [32/44.1/48kHz only] ...and I mainly tune up tone/noise masking and noise normalization parameters. The above change is applied below quality3. 2005/11/05 Aoyumi ---------------------------------------------------------------------------- aoTuV beta4 technical information The differences from the aoTuV beta 3... 1. Adoption of new hypot (point stereo). This works in general better than dipole/round hypot. And when residue is likely to decrease greatly at the time of a reverse phase, added code is made to increase the ratio of lossless. 2. Change of ATH curve. This is not a big change. 3. Residue used for threshold calculation of channel coupling is changed. This one seems to be good selection. 4. HF reduction code of beta3 was deleted. Now, this is not required. 5. The energy deficit of M4 code of beta3 -- correction of a bug Now. 6. The code for pulling downward floor of the frequency range which can be easy to be heard was added (New M2). This works by the low bit rate and has a comparatively good trade-off. 7. Change of threshold calculation of noise normalization. Moreover, it takes phase information into consideration. ...and I mainly tune up tone/noise masking and noise compander parameters. 2005/06/18 Aoyumi ---------------------------------------------------------------------------- aoTuV beta3 technical information The differences from the aoTuV beta 2 and Vorbis 1.1... 1. Dynamic impulse block noise control(q0-10). [32/44.1/48kHz only] Conspicuous pre-echo is reduced. 2. New ATH curve. 3. In order to cancel that a small sound becomes unstable, the noise level of low frequency is lowered under specific conditions. (Only below q3) There is a greatest effect on a piano etc. [32/44.1/48kHz only] 4. The rate of lossless stereo is increased in specific conditions. This improves many of conspicuous problems which a point stereo causes. (e.g drumus's hiss/voice, guitar and brass's distortion) [32/44.1/48kHz only] 5. The action of the noise normalization of point stereo is corrected. It was set to one of the causes of distortion in a long tone (e.g strings/oboe/high tone voice). 6. The HF reduction code was not working normally. This is corrected and it retuned up according to the present condition. [32/44.1/48kHz only] 7. The q-2 mode was added in all sampling frequencies. And nominal bitrate of q-1 are changed into a more nearly average value. Although nominal bitrate is more large at a low sampling frequency, average bitrate hardly differs from the former version. ...and I mainly tune up tone/noise masking parameters. 2004/11/21 Aoyumi