Chip16 Official thread (Development/Suggestions)

[paul_nicholls]

Originally Posted by tykel

I think it looks good. Once there is a consensus I will be able to add it to the next revision of the spec, along with PAL.
Just clarify one thing for me, what is the frequency for? How does it differ from the sample rate?

Ok, the frequency of the sound is like the musical note you can hear like when you play middle C on a piano for example, and it is how many cycles a sound wave goes trough each second and is measured in Hertz (Hz).

Here is a table of musical note frequencies:
http://www.phy.mtu.edu/~suits/notefreqs.html

and here is some ASCII art I created to try and explain it better:

volume  +1      |--------|
                |        |
                |        |
                |        |
        0                |        |
                         |        |
                         |        |
volume  -1               |--------|


                0                 1 second

                <----------------->
                       time

A frequency of 1Hz means the waveform does one full cycle (as above) in 1 second time period.

It is entirely possible for the waveform to have more cycles per second (> 1Hz), or less cycles per second (< 1Hz).

So a waveform with a frequency of 120.5Hz means it 'fits' 120.5 full cycles of itself in a 1 second time period.

Now, the sample rate is how many samples, or discrete parts of an analog signal, is read per second to re-create a digital version of the original analog signal.

So the more samples per second (Hz) you have when sampling an analog signal, the better, or smoother the reproduction is (and better sound quality). The downside is that it takes more memory (or disk space) to store that sound because of more samples per second.

But that is not an issue for us as we are only playing it in memory and it won't hang around very long.

See here for a good description of sampling rate:
http://en.wikipedia.org/wiki/Sampling_rate

Does this help a bit?

cheers,
Paul