Audio Compressor project - any one done one yet?

[ubergrafik]

Hi teensy folk,

I was hoping to create an audio compressor using a teensy and the audio board. I am wondering if any one has made one yet, or have any suggestions.

In general terms, it would need to do the following:

audio input > level detection > if above level set by THRESHOLD knob, reduce volume by amount set by the RATIO knob
It also has an attack and release setting for how quickly the gain reduction starts and ends after the threshold is reached...
As well as a gain makeup at the end to bring the whole level up.

It would need audio in/out and a few pots to control the various settings.

Thanks in advance!

 

[mxxx]

not that i know.

AFAIK, the sgtl5000 comes with some inbuilt compressor-esque functions, which seem to work ok (haven't tried myself); see here, for example: https://forum.pjrc.com/archive/index.php/t-27526.html

more demanding, i figure, would be to implement them in software. here, for instance, is some fixed point code (for stm32F10x), so should be portable to teensy 3.x with some patience ...

 

[ubergrafik]

Thanks for the quick response! I will look in to what the sgtl5000 does. Sounds like it is more or less what I am after functionality wise. I'd be keen to know what it sounds like (I haven't got one yet!)

Yeah, coding it could be a challenge, but may result in something better sounding... Will try the easy option first

Thanks again!

 

[Pensive]

The bitcrusher example shows the onboard compressor running, it's OK, but limiting as a post processor on the "What-u-hear" output. I found it tricky to adjust to get a pleasing sound.

I think the audio library will way outlast the SGTL5000 so it would be a good idea to implement a software one.

Compression is usually applied heavily on drums and guitar but less so on vocals / samples etc, truth is you need a setting for every track if you really want a good mix.

Whats good for drums, might ruin vocals for example.

Of course it depends on your project as to whether this matters at all.

 

[MacroMachines]

@pensive compressor design is kinda tricky, I found that you really have to dig into linear vs log dB scaling and different averaging schemes for the attack and decay, I made a pretty good audulus implimentation so I can likely port that to teensy soon enough. I think my plan right now is to make multiple different quality solutions that have compilation flags to allow quality vs CPU use decisions readily.