1 ## 7.8\. Audio 2 3 ### 7.8.1\. Microphone 4 5 If device implementations include a microphone, they: 6 7 * [C-1-1] MUST report the `android.hardware.microphone` feature constant. 8 * [C-1-2] MUST meet the audio recording requirements in 9 [section 5.4](#5_4_audio_recording). 10 * [C-1-3] MUST meet the audio latency requirements in 11 [section 5.6](#5_6_audio_latency). 12 * [SR] Are STRONGLY RECOMMENDED to support near-ultrasound recording as described 13 in [section 7.8.3](#7_8_3_near_ultrasound). 14 15 If device implementations omit a microphone, they: 16 17 * [C-2-1] MUST NOT report the `android.hardware.microphone` feature constant. 18 * [C-2-2] MUST implement the audio recording API at least as no-ops, per 19 [section 7](#7_hardware_compatibility). 20 21 22 ### 7.8.2\. Audio Output 23 24 If device implementations include a speaker or an audio/multimedia output 25 port for an audio output peripheral such as a 4 conductor 3.5mm audio jack or 26 USB host mode port using [USB audio class]( 27 https://source.android.com/devices/audio/usb#audioClass), they: 28 29 * [C-1-1] MUST report the `android.hardware.audio.output` feature constant. 30 * [C-1-2] MUST meet the audio playback requirements in 31 [section 5.5](#5_5_audio_playback). 32 * [C-1-3] MUST meet the audio latency requirements in 33 [section 5.6](#5_6_audio_latency). 34 * [SR] STRONGLY RECOMMENDED to support near-ultrasound playback as described 35 in [section 7.8.3](#7_8_3_near_ultrasound). 36 37 If device implementations do not include a speaker or audio output port, they: 38 39 * [C-2-1] MUST NOT report the `android.hardware.audio.output` feature. 40 * [C-2-2] MUST implement the Audio Output related APIs as no-ops at least. 41 42 43 For the purposes of this section, an "output port" is a 44 [physical interface](https://en.wikipedia.org/wiki/Computer_port_%28hardware%29) 45 such as a 3.5mm audio jack, HDMI, or USB host mode port with USB audio class. 46 Support for audio output over radio-based protocols such as Bluetooth, 47 WiFi, or cellular network does not qualify as including an "output port". 48 49 #### 7.8.2.1\. Analog Audio Ports 50 51 In order to be compatible with the [headsets and other audio accessories]( 52 http://source.android.com/accessories/headset-spec.html) 53 using the 3.5mm audio plug across the Android ecosystem, if a device 54 implementation includes one or more analog audio ports, at least one of the 55 audio port(s) SHOULD be a 4 conductor 3.5mm audio jack. 56 57 If device implementations have a 4 conductor 3.5mm audio jack, they: 58 59 * [C-1-1] MUST support audio playback to stereo headphones and stereo headsets 60 with a microphone. 61 * [C-1-2] MUST support TRRS audio plugs with the CTIA pin-out order. 62 * [C-1-3] MUST support the detection and mapping to the keycodes for the 63 following 3 ranges of equivalent impedance between the microphone and ground 64 conductors on the audio plug: 65 * **70 ohm or less**: `KEYCODE_HEADSETHOOK` 66 * **210-290 ohm**: `KEYCODE_VOLUME_UP` 67 * **360-680 ohm**: `KEYCODE_VOLUME_DOWN` 68 * [C-1-4] MUST trigger `ACTION_HEADSET_PLUG` upon a plug insert, but 69 only after all contacts on plug are touching their relevant segments 70 on the jack. 71 * [C-1-5] MUST be capable of driving at least 150mV 10% of output voltage on 72 a 32 ohm speaker impedance. 73 * [C-1-6] MUST have a microphone bias voltage between 1.8V ~ 2.9V. 74 * [SR] STRONGLY RECOMMENDED to detect and map to the keycode for the following 75 range of equivalent impedance between the microphone and ground conductors 76 on the audio plug: 77 * **110-180 ohm:** `KEYCODE_VOICE_ASSIST` 78 * SHOULD support audio plugs with the OMTP pin-out order. 79 * SHOULD support audio recording from stereo headsets with a microphone. 80 81 82 If device implementations have a 4 conductor 3.5mm audio jack and support a 83 microphone, and broadcast the `android.intent.action.HEADSET_PLUG` with the 84 extra value microphone set as 1, they: 85 86 * [C-2-1] MUST support the detection of microphone on the plugged in audio 87 accessory. 88 89 ### 7.8.3\. Near-Ultrasound 90 91 Near-Ultrasound audio is the 18.5 kHz to 20 kHz band. 92 93 Device implementations: 94 95 * MUST correctly report the support of 96 near-ultrasound audio capability via the [AudioManager.getProperty]( 97 http://developer.android.com/reference/android/media/AudioManager.html#getProperty%28java.lang.String%29) 98 API as follows: 99 100 If [`PROPERTY_SUPPORT_MIC_NEAR_ULTRASOUND`]( 101 http://developer.android.com/reference/android/media/AudioManager.html#PROPERTY_SUPPORT_MIC_NEAR_ULTRASOUND) 102 is "true", the following requirements MUST be met by the 103 `VOICE_RECOGNITION` and `UNPROCESSED` audio sources: 104 105 * [C-1-1] The microphone's mean power response in the 18.5 kHz to 20 kHz band 106 MUST be no more than 15 dB below the response at 2 kHz. 107 * [C-1-2] The microphone's unweighted signal to noise ratio over 18.5 kHz to 20 kHz 108 for a 19 kHz tone at -26 dBFS MUST be no lower than 50 dB. 109 110 If [`PROPERTY_SUPPORT_SPEAKER_NEAR_ULTRASOUND`]( 111 http://developer.android.com/reference/android/media/AudioManager.html#PROPERTY_SUPPORT_SPEAKER_NEAR_ULTRASOUND) 112 is "true": 113 114 * [C-2-1] The speaker's mean response in 18.5 kHz - 20 kHz MUST be no lower 115 than 40 dB below the response at 2 kHz. 116
