Rich Peet, you wrote,
>I have played a lot with various compressions.
>For nature recordists I recommend to never use a VBR compression.
>
>What happens is your quiet backgrounds become much more deteriorated
>than what happens in highly saturated music files.
Thanks for that observation.
>As general advise of how to compress in MP3 for nature recordings, I
>recommend that you look at a spectral display of the sound and write
>down the highest pitch that you wish to preserve. Then compress the
>file with the highest bit rate possible using the lowest sample rate
>to retain that highest pitch. If your highest pitch is 8,000 cycles
>you need a sample rate of double that or 16,000 to retain that pitch.
It's important to not confuse compression bit rate with sample rate.
MP3 files are almost always 44.1KHz -sample rate-, but they can be
compressed at different -bit rates- (128K is common, I use 192K for
high quality). Lower -bit- rates give lower quality, not frequency
response. Lower -sample- rates make a lower high frequency response
cutoff. I don't think low sample rates (like 32KHz, 22KHz) are used
much any more, except maybe in a closed environment like games
programming.
-Dan Dugan
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