ChromeOS Compatible - 3.5mm Headset Specification v1.3

Version: 1.3.1
Last updated: 2024-06-17

Legend

Product Verb Development Action
"MUST" Mandatory product requirement
"SHOULD" Optional recommendation
"MAY" Nice to have

Overview

This document describes the requirements a ChromeOS Compatible wired headset meets. This specification is not for WWCB products, nor for a product designed and certified together with a Chromebook.

3.5mm audio connector hardware specifications

Plug

  • Mechanical
    • 4 conductor 3.5mm plug
    • Pinout order
      • CTIA (LRGM) - Recommended
      • OMTP(LRMG) - Optional
  • Electrical
    • Ear speaker impedance
      • ≥ 16 Ω
    • Mic equivalent DC resistance
      • ≥ 1000 Ω

Buttons

  • Only buttons listed below are allowed
    • Play/Pause (Function A)
    • Volume up (Function B)
    • Volume down (Function C)
  • Mandatory
    • No answer/hang up button.
      • The OS doesn’t support it.

  • The control function equivalent Impedance* must satisfy the requirements in the table below:

    Function Impedance1 range
    Play/Pause (Function A) [0, 70] Ω
    Volume up (Function B) [210, 290] Ω
    Volume down (Function C) [370, 680] Ω

headset test circuit schematic

(Source: https://source.android.com/devices/accessories/headset/plug-headset-spec )

Audio Quality

Capture Path - Mute

  • If there is any interface for users to mute the audio device, it must
    • Maintain the mute state in a way that is not affected by:
      • Opening and closing the device.
      • Switching to another input device.
  • If the user presses the mute button on the headset or ChromeOS, the mute state must change.
  • If the mute state changes, the mute state indicator (eg:LED) on the headset must change.

Audio Latency

Latency

  • Output Latency
    • Audio playback must begin ≤500 ms after a user action that initiates playback.
      • May request a waiver if the device OEM can prove that no echo is introduced when it fails this requirement.

A/V Sync

  • Audio playback should be synchronized with video playback. Audio playback may lead the video by ≤25 ms or trail the video by ≤95 ms.

Revision History

Date Version Notes
2024-06-17 1.3.1 ChromeOS Compatible spec derived. Initial Partner Site Publication.
2022-09-01 1.3 Related WWCB specification v1.3
2022-06-06 1.2 Related WWCB specification v1.2
2020-10-14 1.1 Related WWCB specification v1.1
2020-09-23 1.0 Related WWCB specification created.

  1. The equivalent impedance is measured from positive mic terminal to GND when button is pressed with 2.2 V mic bias applied through 2.2 kΩ resistor. ↩