7.8. Audio
7.8.1. Microphone
If device implementations include a microphone, they:
- [C-1-1] MUST report the
android.hardware.microphone
feature constant. - [C-1-2] MUST meet the audio recording requirements in section 5.4.
- [C-1-3] MUST meet the audio latency requirements in section 5.6.
- [SR] Are STRONGLY RECOMMENDED to support near-ultrasound recording as described in section 7.8.3.
If device implementations omit a microphone, they:
- [C-2-1] MUST NOT report the
android.hardware.microphone
feature constant. - [C-2-2] MUST implement the audio recording API at least as no-ops, per section 7.
7.8.2. Audio Output
If device implementations include a speaker or an audio/multimedia output port for an audio output peripheral such as a 4 conductor 3.5mm audio jack or USB host mode port using USB audio class, they:
- [C-1-1] MUST report the
android.hardware.audio.output
feature constant. - [C-1-2] MUST meet the audio playback requirements in section 5.5.
- [C-1-3] MUST meet the audio latency requirements in section 5.6.
- [SR] STRONGLY RECOMMENDED to support near-ultrasound playback as described in section 7.8.3.
If device implementations do not include a speaker or audio output port, they:
- [C-2-1] MUST NOT report the
android.hardware.audio.output
feature. - [C-2-2] MUST implement the Audio Output related APIs as no-ops at least.
For the purposes of this section, an "output port" is a physical interface such as a 3.5mm audio jack, HDMI, or USB host mode port with USB audio class. Support for audio output over radio-based protocols such as Bluetooth, WiFi, or cellular network does not qualify as including an "output port".
7.8.2.1. Analog Audio Ports
In order to be compatible with the headsets and other audio accessories using the 3.5mm audio plug across the Android ecosystem, if a device implementation includes one or more analog audio ports, at least one of the audio port(s) SHOULD be a 4 conductor 3.5mm audio jack.
If device implementations have a 4 conductor 3.5mm audio jack, they:
- [C-1-1] MUST support audio playback to stereo headphones and stereo headsets with a microphone.
- [C-1-2] MUST support TRRS audio plugs with the CTIA pin-out order.
- [C-1-3] MUST support the detection and mapping to the keycodes for the following 3 ranges of equivalent impedance between the microphone and ground conductors on the audio plug:
- 70 ohm or less:
KEYCODE_HEADSETHOOK
- 210-290 ohm:
KEYCODE_VOLUME_UP
- 360-680 ohm:
KEYCODE_VOLUME_DOWN
- [C-1-4] MUST trigger
ACTION_HEADSET_PLUG
upon a plug insert, but only after all contacts on plug are touching their relevant segments on the jack. - [C-1-5] MUST be capable of driving at least 150mV ± 10% of output voltage on a 32 ohm speaker impedance.
- [C-1-6] MUST have a microphone bias voltage between 1.8V ~ 2.9V.
- [SR] STRONGLY RECOMMENDED to detect and map to the keycode for the following range of equivalent impedance between the microphone and ground conductors on the audio plug:
- 110-180 ohm:
KEYCODE_VOICE_ASSIST
- SHOULD support audio plugs with the OMTP pin-out order.
- SHOULD support audio recording from stereo headsets with a microphone.
If device implementations have a 4 conductor 3.5mm audio jack and support a microphone, and broadcast the android.intent.action.HEADSET_PLUG
with the extra value microphone set as 1, they:
- [C-2-1] MUST support the detection of microphone on the plugged in audio accessory.
7.8.3. Near-Ultrasound
Near-Ultrasound audio is the 18.5 kHz to 20 kHz band.
Device implementations:
If PROPERTY_SUPPORT_MIC_NEAR_ULTRASOUND
is "true", the following requirements MUST be met by the VOICE_RECOGNITION
and UNPROCESSED
audio sources:
- [C-1-1] The microphone's mean power response in the 18.5 kHz to 20 kHz band MUST be no more than 15 dB below the response at 2 kHz.
- [C-1-2] The microphone's unweighted signal to noise ratio over 18.5 kHz to 20 kHz for a 19 kHz tone at -26 dBFS MUST be no lower than 50 dB.
If PROPERTY_SUPPORT_SPEAKER_NEAR_ULTRASOUND
is "true":
- [C-2-1] The speaker's mean response in 18.5 kHz - 20 kHz MUST be no lower than 40 dB below the response at 2 kHz.