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2

Here is an example of what the modern preprocessing Tommy is alluding to actually sounds like: er1.ssd er2.ssd er3.ssd. This is encoded using pcmenc, storing 4-bit volumes for each of the three tone channels in turn, evenly spaced at 35294Hz, so this is 12-bit sampling at 11.7kHz or 4-bit sampling at 35.3kHz depending on how you want to look at it. At an ...


6

Here's how the specific routine you posted works. It appears to be using the "4-bit linear" method mentioned on this page. The resulting samples are not truly linear, but it's easy to understand and implement, and good enough for game SFX or speech. We'll analyse this in bottom-up order, starting with the last routine, which simply takes a ...


5

The BBC Micro uses an SN76489, which provides three tone channels each with sixteen volume levels. For speech playback the standard approach is to set the channels in use to a very high frequency and then modulate the volume. For each channel the volumes are a logarithmic scale, where each step is approximately 10^-0.1 as loud as the previous, i.e. around 79%...


13

No, it can not be used to sample audio. As the link you provided says, in 12-bit mode it takes 10 milliseconds to convert a sample, and even in 8-bit mode it takes 4 milliseconds. That results into maximum sampling rate of 250 Hz, which is useless for sampling audio. The low sampling rate indicates the analog input is meant for slowly changing signals, like ...


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