This should hopefully fix poor audio quality during video recording on the Pixel 3.
Google is starting off the new year strong with the rollout of the January 2019 security patch for its Pixel line of devices. Per the Pixel Update Bulletin, this update fixes a number of security issues, the most severe of which allowed remote attackers to use a specially crafted file to execute arbitrary code within the context of a privileged process.
For Pixel 3 and 3 XL owners, this update also improves audio quality while recording video — something many users have complained about since the devices’ release.
The January 5, 2019 security patch should be rolling out to all Pixel devices shortly (you can manually check by tapping the System update button within the System section of the Settings app), but if you don’t want to wait, you can manually flash it using the appropriate factory image for your device — PQ1A.190105.004 for the Pixel 3, PQ1A.190105.004 for the Pixel 2, PQ1A.190105.004 for the original Pixel, and OPM8.190105.002 for the Pixel C tablet (which still runs Android 8.1 Oreo).