istor-alpha6

• Added audio controls for the Clearwater chipset
  • Headphone stereo volume
  • Mono mixer
  • 8-band stereo equalizer with combined or per-channel gains
  • Synapse controls available: Preview

This is an implementation which uses all 4 hardware equalizers of the audio chip. I cascade 2 equalizers on each stereo channels to achieve a full fledged 8-band equalizer instead of 5 bands on previous Wolfson implementations. This should give some better fine-grained controls over the conventional equalizers we've seen in the past. On top of this, I implemented the option to control the equalizer gains on a per-channel basis instead of a combined manner. Samsung here had the right idea with Adapt Sound to calibrate for each ear as people's ears or headphones can differ between left/right. I recommend using Adapt Sound to find out what the frequency response of your headphones and hearing is, and depending on that, to try to use the hardware equalizer to get a flat response (While disabling Adapt Sound itself).

This of course also brings the usual left/right volume controls as well as mono mixing.

I didn't include speaker controls for a few reasons; the S6 uses an external Maxim audio amplifier on top of the Wolfson audio chipset. The default ALSA settings do some quite advanced DSP processing for the speaker, something I didn't have time to fully research. For now, I just included volume control for the phone's earpiece.

For advanced users who want to maximise their audio quality, the equalizer's frequency band settings are exposed via sysfs and can be set via WISCE. I set up the default bands at 25/200/500/1000/2000/4000/8000/16000KHz with the non-cutoff frequencies having bandwidths of 1/2 their center-frequency.