Subject: Re: [linux-audio-dev] decoding mp3 files
From: tim (tim_AT_ipd50abcd9.speed.planet.nl)
Date: Fri Jun 07 2002 - 21:47:07 EEST
> Paul Davis <pbd_AT_op.net> wrote:
> > i don't know precisely whats going on there, but mp3 is a *lossy*
> > compression technique. whether or not the data size is the same or
> > not, you will not get the same data back after the mp3 cycle as you
> > started with. this isn't a decoder-specific issue - its inherent to
> > the way mp3 works. comparing two wavs that have been through this
> > process will never find them to be the same.
>
> Yes. This is exactly what I want to do ! I wanna compare several
>codecs for their quality. [.....]
i would be interested to know which psyco-acoustic model
you are going to use to determine subjective quality. Perhaps
you could elaborate on what you mean by quality - there have
been reports recently that tried to evaluate lossy audio
encoders by doing standard measurements, but while interesting, they
are of limited value, as the trade offs used by the codecs
are designed for minimal _subjective_ loss.
sorry i cant help you with the front offsets. I doubt this is
a rigid part of the mp3 spec, but even if it were, there is no
guarantee that all encoders actually conform. You may have to
just try the different encoders. Dont forget to remove the
v2 id tag from the beginning AND the v1 id tag from the end.
The format of these tags is well documented.
Good luck!
-- Tim Orford
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