Headphone jack/external mic specifications

[jensigner]

I'm interested in getting more detailed specs and information on the S4 headphone output drive circuit. Is it similar to the S3? Is the output driver (and microphone input) chip a Wolfson device and is the microphone input impedance requirement still 1kohm as stated here for the S3?
How to add external mic to Galaxy Camera, SIII and Note 2 | Ruchirablog

Also of interest:
Wolfson Microelectronics | Multi-Year IP License and Component Supply Agreement with Samsung establishes Wolfson as a primary audio partner for GALAXY range of smartphones and tablets