> The de-emphasis in mpeg audio is only a flag to indicate if emphasis was
> applied on hte source or not, in order to compensate it in the decoder.
> There is nothing to do about it in the encoder, except positionning the
> flag.
>
> But those 2 emphasis (C/5) are now obsolete for a lot of years. This flag
> was removed in AAC and mpeg-4.
>
In the Resampling Audio Package, Julius O. Smith said
"Any reasonable sampling rate can be converted to any other. (Note
that, in this example, if you have obtained a direct-digital transfer
from DAT or CD, you probably have some pre-emphasis filtering which
should be canceled using a digital filter."
Since one goal of Lame is to be able to resample, we should let the user
decide if the source had pre-emphasis. In the case it had, Lame would have
to cancel it and put the flag emphasis to 0 before resampling. The package
of JO Smith is not out-dated (06/99) so we should consider his remark before
removing the emphasis. Another question is : which CD's or DAT's have
pre-emphasis ?
Regards
Lionel
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