Hello andrew,
Tuesday, July 25, 2000, 12:19:20 AM, you wrote:
ac> When decoding mp3s to .wav (1) and using Cool Edit's Spectral View (2), to my
ac> surprise I've noticed an obvious treble cut beyond 16KHz on VBR mp3s (3) I've
ac> encoded with LAME. Is this intentional?
How many different music pieces did you test to conclude that? I know
some have an average cut>16kHz, but there are reasons for this.
ac> Fortunately CBR mp3s (4) do not appear to suffer the same audio degredation.
There is no audio degradation here imho
ac> See http://homepages.ihug.com.au/~ozzmosis/lame-tests/ for an example.
ac> Notes:
ac> (1) Winamp 2.64 was used to decode to .wav.
best use "lame --decode", as it's the only correct decoder around
(check that decoding site) (but it makes no difference here)
ac> (2) Cool Edit's Frequency Analysis (Alt+Z) can also be used to demonstrate
ac> this, but remember to select the entire waveform Ctrl+A beforehand.
ac> (3) VBR mp3s were made using LAME 3.85 with "lame -V1 -b128 -h -k -mj -q1"
ac> options.
verified
ac> (4) CBR mp3s were made using LAME 3.85 with "-b224 -h -k -mj -q1" options.
verified
What happens imho, is that in the last few seconds you have a high
freq and a low freq signal (the low voice). Whenever the low voice
pops up in the song, the high freq (>16kHz) drops to the bottom of the
graph. (leave the freq analysis window open and then press play to see
this)
My best guess is that the low freq signal simply masks the >16kHz
tones when it occurs. This is quite often, -> average dB's of >16kHz
drop in a ctrl-a graph.
This is normal because in VBR mode the psycho-accoustic model
determines which tones are masked by which, and at the times that
heavy voice comes through, all high tones are masked => left out in
the vbr mp3.
I cannot hear a difference, nor some sort of artifacts.
I think there is no problem, and the psycho-accoustics work fine.
Roel/r3mix
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Best regards,
Roel mailto:[EMAIL PROTECTED]
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