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Why are 128kbit/s MP3s usually 44,100 Hz?
eamon123
post Oct 14 2012, 01:44
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Since 128kbit/s MP3s usually has a low-pass filter at 16,000 Hz, and the Nyquist-Shannon theorem states that all frequencies under f/2 Hz can be totally described at an f Hz sampling rate, why not encode at 32,000 Hz? Wouldn't it save more space?
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saratoga
post Oct 14 2012, 04:03
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QUOTE (eamon123 @ Oct 13 2012, 20:44) *
Since 128kbit/s MP3s usually has a low-pass filter at 16,000 Hz, and the Nyquist-Shannon theorem states that all frequencies under f/2 Hz can be totally described at an f Hz sampling rate, why not encode at 32,000 Hz? Wouldn't it save more space?


Since encoding happens in the frequency domain anyway, there isn't much savings. It'll just not encode those frequencies, which is pretty close to downsampling, but much easier to implement.

That said, at very low bitrates LAME does downsample.
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