Pixel does have Qualcomm Aquatic
However judging by the mixer_path.xml setting discrepancies when compared to HTC 10, Snapdragon Note 7, Xiomia Mi5 ; Pixel settings are not on HIFI and thus I feel the audio was not optimized.
[Rx Headphone Mode value =CLS_H_HIFI on all but Pixel.
Pixel reads CLS_H_LOHIFI, which doesn't match the other Aqstic value settings]*
Specs for Aqstic
https://www.qualcomm.com/products/snapdragon/processors/821)
Audio
Audio Technology
Qualcomm Aqstic™ audio technology
Qualcomm Aqstic™ audio codec playback support
192kHz 24-bit lossless audio playback
Qualcomm Aqstic™ Speaker Amplifier output power
Up to 4W output power
Qualcomm Aqstic™ technology
Qualcomm Aqstic™ audio codec
Qualcomm Aqstic™ speaker amplifier with Speaker Protection
If you look at Qualcomm Snapdragon 820 feature set listed on their site; the Aqstic is missing as a feature. : www.qualcomm.com/products/snapdragon/processors/820
I think the 8996 processor with Aqstic was changed to an 821 for classification sakes. Which is why there is no speed changes and mainly just the Efficiency which could also be contributed to the Aqstic DAC/amp. Since Qualcomm advertises improved efficiency utilizing Aqstic over their initial 820 SOC offering.
Looking at the specifications of the Aqstic DAC/codec/amp some optimization definitely seems to be missing from the Pixel devices.
LG went a different route by not paying Qualcomm for Aqstic Audio access and thus implementing their own DAC/AMP solution.
HTC said they weren't using the standard Snapdragon 820 SOC audio offering, but have not dented using Aqstic which Qualcomm says HTC 10 was using Aqstic.
With HTC Bolt lacking Headphone Jack....I'm really hoping HTC doesn't make no Headphone Jack the norm.
That would only leave LG as offering built-in Headphone optimization.
Seems like a crazy industry move, just when Qualcomm actually gave a noteworthy effort in terms of Aqstic specs. (Yet, the manufacturers are abandoning the Headphone Jack...like sorry Qualcomm but it is too late)