[Lame]ATH wat is het, wat kan je er aan instellen?

[Verwijderd]

Vroeg ik me af... klinkt zo magisch enzo, als je dan encode, pshychoaccoustics ofzo...
Hier, dit bedoel ik:


Wat is het nou en kan je het beter zo laten of kan je er nog iets aan veranderen?

[Verwijderd]

Never mind... r3mix is al ingesteld e.d.... veel beter dan zelf instellen volgens mij

[guillaume]

Je hebt wel gelijk denk ik, gewoon --r3mix gebruiken...

[Anton]

Zie www.r3mix.net, onder Quality:

What's "athtype 3"?

ATH stands for "Absolute Treshold of Hearing". (aka "minimal audition threshold" ) It is the characteristic which plots the minimal volume the human ear can perceive at a certain frequency. The area under the curve contains sounds at unaudible volume. If you read the graph correctly you can see that starting at about 4kHz the human ear becomes less sensitive with raising frequency.

Mp3 won't encode sounds situated under this threshold. This also means mp3 will tolerate distortions as long as their volume is under the ATH curve, because these will be inaudible to the listener.

Upto version 3.87 the "Type 0: Painter & Spanias" ath curve was used in LAME. Problem with this curve was that it was too inaccurate starting from about 13kHz leaving the higher music frequencies (HF) relatively under-emphasized compared to the lower frequencies. In some music clips this allowed lame to create HF artifacts because the encoder assumed they were "unaudible", which wasn't the case at all.

After a great deal of listening tests and tweaks it was found that lowering the HF region of the ATH curve solved just about all HF artifacts. Two new ATH curves were introduced into lame. "Type 1" which was by Frank Klemm and "Type 2" by Gabriel Bouvigne. Of course higher accuracy in the HF area, which is the hardest to encode, comes with higher bitrate demands. This is why my own "Type 3" was derived from "Type 2". In combination with a lowpass filter it tries to compensate for HF bitrate demands by lowering LF emphasis and using a 19.5kHz lowpass filter. On the graph you see in the type0-type3 transition bits are taken from the gray LF area which are later invested in the green HF area. With success.