The "--notemp" switch in LAME

2003-07-25 11:10:52

Hi,

Could anybody tell me about "--notemp" switch in lame?

The help only says "Don't make use of the temporal masking effect".
What does it mean and how this switch can affect the results of encoding?

Thank you very much in advance.

Best regards,
Leonid Zhigunov.

The "--notemp" switch in LAME

Reply #1 – 2003-07-25 14:00:42

It's practically for testing purposes only.
Temporal masking:
http://ccrma-www.stanford.edu/~bosse/proj/node21.html

The "--notemp" switch in LAME

Reply #2 – 2003-07-25 14:32:12

Use of it will decrease quality, especially at low bitrates.

The "--notemp" switch in LAME

Reply #3 – 2003-07-25 15:07:38

Thanks for your reply.

I was not sure about the temporal masking.
Now I understand, that it is exactly what I thought.

I experimented with "--notemp" switch and got the results,
which I can not understand.

I have created two MP3 files with and without --notemp switch,
using -V0 -b 128.
They differs in size (which is obvious), but the sound is
also slightly different. Some instuments and sounds in the
background sound louder in --notemp MP3, than in the original
WAV. (Not worse, the sound is great, but little louder and clear,
i.e. I can distinguish sounds, which are almost indistinguishable
in the original WAV). While the MP3 created without --notemp
sounds like an original.

How it can be possible?
As far as I understand, I should not hear the masked sounds
regardless of their presence. I mean, if I can not phisically hear
something in the original WAV, because of the masking effect,
I should not phisically hear it in the encoded MP3 as well (again
because of masking).

Or may be I am totaly wrong about masking?
Or --notemp causes some other effects else?

I will be very appreciated for any comments or explanations.

Regards,
Leonid