audio processing

[Patrick Perdue]

Greetings:

I am not an iOS developer, so I know nothing.

I'm curious, though, if any changes can be made to audio processing by
developers of call kit applications, such as repeaterphone. I expect
probably not, that it's either on or off.

I have never really liked the AGC curve it uses, and there is a bit of a
weird kind of EQ curve that could certainly be better, whether you use
repeaterphone or are just making normal phone calls. I'm glad that
repeaterphone allows disabling audio processing. I normally use it this
way with wired headphones and more gain, being very careful about the
application, but of course, most call kit applications don't allow for
this, and you wouldn't want that in normal situations anyway, since that
kills echo cancellation.


73

N2DYI

[Weston Bustraan]

There isn't much in the way of configuration exposed to developers, but It appears that it may be possible to disable the AGC. 

https://developer.apple.com/documentation/audiotoolbox/kauvoiceioproperty_voiceprocessingenableagc

I guess the question is; is no AGC better than a poor AGC curve?

- Wes W8WJB

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[Patrick Perdue]

Considering I have never seen a configuration where processing is enable but with no AGC, didn't know that was even possible, I honestly don't know the answer to that. The existing AGC curve is... well, far less than optimal, though, and has been for years, since at least iOS 7.

I wonder, though, if this leaves room to insert something else in the chain that would be better suited for that purpose. Even just a fine-tuned general purpose single-band compressor.

The big problem now is that, if there is nothing much going on, the AGC digs and digs, to the point where, when someone keys up in a quiet room, they are blastingly loud for about a second, until AGC figures things out and turns the audio down. It has a very slow attack.

I have discovered that, if you just say "uh" at a reasonable volume before keying up, it will get the AGC to a more tolerable point before you start transmitting, but who's going to do that?