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<p>Imagine you have an audio hardware that can only output 8-bit
samples but that has a samplerate of 1 million samples per second.</p>
<p>That means you would only be able to output 256 separate values
(0...255). But if you really wanted to output the value 128.5 you
could nearly do so by alternating between outputting an 128 and an
129.</p>
<p>The easiest way to archive this result is to add a small signal
of the height +/-0.5 values to your audio data. Ardour now allows
you to choose what shape this signal has: <br>
</p>
<ul>
<li>None: The additional signal is zero. If you want to output an
an 128.5 your output signal is rounded, presumably to 129.<br>
</li>
<li>Rectangular: The additional signal alternates between 2
values. Which means your audio signal's resolution is
effectively increased by only 0.5 bits at the cost of
introducing an extremely low buzzing that using today's sample
rates always lies outside the audible range.</li>
<li>Triangular: The additional signal is of a triangular shape.
Which means the audio resolution is increased more than with
setting "rectangular". But the additional signal that allows to
do this is in the audible frequency range and is at a single
frequency so if you krank up the volume of your stereo while the
input signal's amplitude is extremely low you might be able to
hear the triangular signal.</li>
<li>Shaped Noise: The additional signal is noise with a certain
frequency spectrum. Which means the spectrum of the 0,5 bit high
medium error the dithering introduces during improving the
resolution is spread over a wild range of frequencies. Even if
you krank up your stereo enough to be able to hear a signal of
the hight of only 0.5 samples in this case what you'll hear is a
low-amplitude noise like the one the stereo will produce,
anyway. <br>
</li>
</ul>
<p>Personally I would choose "none" or "shaped noise".</p>
<p>Kind regards,</p>
<p> Gunter.<br>
</p>
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