[icecast] Live stream equalizer

Ross Levis ross at stationplaylist.com
Fri Oct 31 06:48:30 UTC 2003

Hi Christopher

> I was under the impression that "PCM equalizer" means it only equalizes
> PCM codec, i.e. WAV files.

No, not at all.  It equalizes the audio after the decoding of compressed

> Have you noticed a significant quality
> improvement in the EQ for compressed media: MP3, Vorbis, MPC?

Yes, definately.

The Nullsoft MPEG Input plugin has it's own EQ code which can bypassed the
PCM EQ.  This was done initially because it was faster and required much
less CPU than a PCM EQ.  This was in the days when Pentiums were new.  But
for a long time the MPEG plugin has had an optional checkbox to use the PCM
EQ, which was always inferior.

All other input plugins do not have their own EQ code so they utilize the
PCM EQ.  A common complaint until v3.0 and v2.90 was that Ogg Vorbis files
sounded flat and lifeless compared to MP3 in Winamp when using the EQ.  This
was quite obvious on my LPFM station which had a fairly high treble boost
and a mixture of MP3 and OGG.

When v2.90 was released, Nullsoft switched the MPEG plugin to default to the
new PCM EQ.  Now all files are equalized the same.

Ross Levis.

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