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The Android 10 release includes the following
requirements for capture with VOICE_COMMUNICATION.
Implementations should provide an acoustic echo canceler (AEC) on the capture path when
capturing with VOICE_COMMUNICATION.
If providing an AEC, it must be discoverable and controllable through the SDK API's
AcousticEchoCanceler.
The Android platform provides audio effects on supported devices in the
audiofx package, which is available for developers to access.
For example, the Nexus 10 supports the following preprocessing effects:
Preprocessing effects are paired with the use case mode in which the
preprocessing is requested. In Android app development, a use case is referred
to as an AudioSource instance; and app developers request to use the
AudioSource abstraction instead of the actual audio hardware
device. The Android Audio Policy Manager maps an AudioSource instance to a
given capture path configuration (including device, gain, and pre processing) according
to product-specific rules. The following sources are exposed to developers:
The default preprocessing effects applied for each AudioSource instance
are specified in the /vendor/etc/audio_effects.xml file. To
specify your own default effects for every AudioSource instance, create a
/vendor/etc/audio_effects.xml file and specify the
preprocessing effects to turn on. For an example, see the implementation for
the Nexus 10 in device/samsung/manta/audio_effects.xml.
AudioEffect instances acquire and release a session when created and destroyed,
enabling the effects (such as the Loudness Enhancer) to persist throughout the
session.
The following example enables preprocessing for the VoIP
AudioSource and Camcorder AudioSource instances. By declaring
the AudioSource configuration in this manner, the framework
automatically requests the use of those effects from the HAL.
AudioSource tuning doesn't have explicit requirements on audio
gain or audio processing with the exception of voice recognition
(VOICE_RECOGNITION). Requirements for voice recognition include:
Flat frequency response (+/- 3 dB) from 100 Hz to 4 kHz
Close-talk config: 90 dB SPL reads RMS of 2500 (16 bit samples)
Level tracks linearly from -18 dB to +12 dB relative to 90 dB SPL
/device/google/crosshatch/audio_effects.xml file for the Pixel 3
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Last updated 2025-08-29 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-29 UTC."],[],[],null,["# Configure preprocessing effects\n\nThe Android 10 release includes the following\nrequirements for capture with `VOICE_COMMUNICATION`.\n\n- Implementations should provide an acoustic echo canceler (AEC) on the capture path when capturing with `VOICE_COMMUNICATION`.\n- If providing an AEC, it must be discoverable and controllable through the SDK API's `AcousticEchoCanceler`.\n\nThe Android platform provides audio effects on supported devices in the\n[`audiofx`](http://developer.android.com/reference/android/media/audiofx/package-summary.html) package, which is available for developers to access.\nFor example, the Nexus 10 supports the following preprocessing effects:\n\n- [Acoustic\n Echo Cancellation](http://developer.android.com/reference/android/media/audiofx/AcousticEchoCanceler.html)\n- [Automatic Gain Control](http://developer.android.com/reference/android/media/audiofx/AutomaticGainControl.html)\n- [Noise\n Suppression](http://developer.android.com/reference/android/media/audiofx/NoiseSuppressor.html)\n\nPair with AudioSource instances\n-------------------------------\n\nPreprocessing effects are paired with the use case mode in which the\npreprocessing is requested. In Android app development, a use case is referred\nto as an `AudioSource` instance; and app developers request to use the\n`AudioSource` abstraction instead of the actual audio hardware\ndevice. The Android Audio Policy Manager maps an `AudioSource` instance to a\ngiven capture path configuration (including device, gain, and pre processing) according\nto product-specific rules. The following sources are exposed to developers:\n\n- `android.media.MediaRecorder.AudioSource.CAMCORDER`\n- `android.media.MediaRecorder.AudioSource.VOICE_COMMUNICATION`\n- `android.media.MediaRecorder.AudioSource.VOICE_CALL`\n- `android.media.MediaRecorder.AudioSource.VOICE_DOWNLINK`\n- `android.media.MediaRecorder.AudioSource.VOICE_UPLINK`\n- `android.media.MediaRecorder.AudioSource.VOICE_RECOGNITION`\n- `android.media.MediaRecorder.AudioSource.MIC`\n- `android.media.MediaRecorder.AudioSource.DEFAULT`\n\nThe default preprocessing effects applied for each `AudioSource` instance\nare specified in the `/vendor/etc/audio_effects.xml` file. To\nspecify your own default effects for every `AudioSource` instance, create a\n`/vendor/etc/audio_effects.xml` file and specify the\npreprocessing effects to turn on. For an example, see the implementation for\nthe Nexus 10 in `device/samsung/manta/audio_effects.xml`.\n`AudioEffect` instances acquire and release a session when created and destroyed,\nenabling the effects (such as the Loudness Enhancer) to persist throughout the\nsession.\n| **Warning:** For the `VOICE_RECOGNITION` use case, don't enable the noise suppression preprocessing effect. It shouldn't be turned on by default when recording from this audio source, and you shouldn't enable it in your own `audio_effects.xml` file. Turning on the effect by default causes the device to fail the [compatibility requirement](/docs/compatibility) regardless of whether this was on by default due to the configuration file, or the audio HAL implementation's default behavior.\n\nThe following example enables preprocessing for the VoIP\n`AudioSource` and Camcorder `AudioSource` instances. By declaring\nthe `AudioSource` configuration in this manner, the framework\nautomatically requests the use of those effects from the HAL. \n\n```carbon\n\u003cpreprocess\u003e\n \u003cstream type=\"voice_communication\"\u003e\n \u003capply effect=\"aec\"/\u003e\n \u003capply effect=\"ns\"/\u003e\n \u003c/stream\u003e\n \u003cstream type=\"camcorder\"\u003e\n \u003capply effect=\"agc\"/\u003e\n \u003c/stream\u003e\n \u003c/preprocess\u003e\n```\n\nSource tuning\n-------------\n\n`AudioSource` tuning doesn't have explicit requirements on audio\ngain or audio processing with the exception of voice recognition\n(`VOICE_RECOGNITION`). Requirements for voice recognition include:\n\n- Flat frequency response (+/- 3 dB) from 100 Hz to 4 kHz\n- Close-talk config: 90 dB SPL reads RMS of 2500 (16 bit samples)\n- Level tracks linearly from -18 dB to +12 dB relative to 90 dB SPL\n- THD \\\u003c 1% (90 dB SPL in 100 to 4000 Hz range)\n- Near-ultrasound requirements (for testing, see [Near Ultrasound\n Tests](/docs/compatibility/cts/near-ultrasound)):\n - Support for `SUPPORT_PROPERTY_MIC_NEAR_ULTRASOUND` as defined in section 7.8.3 of the CDD.\n - Support for one or both of 44100 or 48000 sampling rates with no band-pass or antialiasing filters.\n- Effects/preprocessing disabled by default\n\nExamples of tuning different effects for different sources are:\n\n- Noise Suppressor\n - Tuned for wind noise suppressor for `CAMCORDER`\n - Tuned for stationary noise suppressor for `VOICE_COMMUNICATION`\n- Automatic Gain Control\n - Tuned for close-talk for `VOICE_COMMUNICATION` and main phone mic\n - Tuned for far-talk for `CAMCORDER`\n\nResources\n---------\n\nFor more information, refer to the following resources:\n\n- Android documentation for [audiofx\n package](http://developer.android.com/reference/android/media/audiofx/package-summary.html)\n- Android documentation for [Noise\n Suppression audio effect](http://developer.android.com/reference/android/media/audiofx/NoiseSuppressor.html)\n- `/device/google/crosshatch/audio_effects.xml` file for the Pixel 3"]]
