Two More Takes
"Doug McDonald" wrote in
message
Arny Krueger wrote:
It is true that the essence of perceptual coding is
eliminating tones that will not be heard anyway,
This is only true at very low, very poor quality,
bitrates, and possibly for very low level high frequency
content.
For good encoders (such as LAME VBR at = 160K) no
"tones are left out".
It's been a while since I did any stress testing on MP3 coders, so I created
a torture test composed of about 36 tones spread from 100 Hz to 10 KHz.
In the old days a test signal like this could trick a coder into actually
dropping one or more of the tones.
The only "perceptual" feature
is how the encoder distributes highly colored noise.
That's pretty what my test encoder did at 160 kbps. However the noise
wasn't really colored, it was something like pink noise.
|