Volume is too LOUD

[ali1234]

In my opinion, the volume slider doesn't have enough range at low volume levels, and too much at high levels. Basically, the lowest volume you can set is too loud for a quiet room, and anything above 50% is absurdly loud.

Volume handling code is here: https://github.com/pimoroni/32blit-beta/blob/master/32blit-stm32/Src/32blit.cpp#L215

This code attempts to do a logarithmic volume control. However, it seems to be actually doing anti-log. I made a graph to plot the output from this function:

https://www.desmos.com/calculator/rzxgdduvi7

H is the value of volume_log_base which is a constant in the code. In the existing code it equals 2. This makes the volume increase quickly at first, and then slowly at higher volumes. This seems backwards to me: it should increase slowly at first, and then quickly at higher volumes. In order to achieve that, H must be less than 1. (At 1 it would behave linearly, except that it causes a division by zero because log(1) = 0.)

From experimentation I have found that a value around 0.04 is needed to get the lowest volume setting suitable for a quiet room (and therefore an even lower value may be desirable).

(Note that this doesn't change how loud the loudest setting is, it just changes how quickly the volume increases.)

[tinwhisker]

Would an 's' curve formula be more suited? This would give greater granularity at either end.

[ali1234]

Not really. Currently there is no discernable difference between the maximum and max-1 volume, while min+1 is about twice as loud as minimum volume. The backlight control behaves in a very similar way too. This is to be expected, because human senses are logarithmic (and the current volume algorithm in the firmware is anti-log ie it makes the problem worse).