Mnyb wrote:
> afaiu the radio itself does not have a built in DSP ( boom has ) and the
> CPU can simply not run any high quality filters .
But the codec chip does have some accessible filter controls that might
be employable in a simple way. I figured out (can't remember how) that
it is a Texas Instruments TLV320AIC3104. I don't know what variant.
As proof of concept I fired up ssh, figured out (yet again) how to use
'amixer', and dug out the datasheet.
To read the current state of the Audio Codec Digital Filter Control
Register:
Code:
--------------------
amixer sget 'Audio Codec Digital Filter Control'
--------------------
Output therefrom:
Code:
--------------------
Simple mixer control 'Audio Codec Digital Filter Control',0
Capabilities: volume volume-joined
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 255
Mono: 0 [0%]
--------------------
As you see, mine returns value '0', i.e. all off. I assume that this the
standard, default, configuration of the Radio.
To turn on each DAC's Digital Effects Filter Control:
Code:
--------------------
amixer sset 'Audio Codec Digital Filter Control' 10
--------------------
To turn off - back to defaults:
Code:
--------------------
amixer sset 'Audio Codec Digital Filter Control' 0
--------------------
I can hear it act as the default filters are switched in and out.
So my programme now advances one step further:
a) Figure out values for the Digital Effects Filter that will give
useful adjustments.
b) Figure out how to engage/disengage them on demand.
(a) Requires a bit of education on how to calculate filter values.
(b) An installable applet. Perhaps suborn the volume control mute action
into doing a little more than just 'mute'.
I think something may be doable, provided it's kept simple and not
required to be perfect under all conditions.
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