1## 5.11\. Capture for Unprocessed
2
3Android includes support for recording of unprocessed audio via the
4`android.media.MediaRecorder.AudioSource.UNPROCESSED` audio source. In
5OpenSL ES, it can be accessed with the record preset
6`SL_ANDROID_RECORDING_PRESET_UNPROCESSED`.
7
8If device implementations intent to support unprocessed audio source and make
9it available to third-party apps, they:
10
11*    [C-1-1] MUST report the support through the `android.media.AudioManager`
12property [PROPERTY_SUPPORT_AUDIO_SOURCE_UNPROCESSED](http://developer.android.com/reference/android/media/AudioManager.html#PROPERTY_SUPPORT_AUDIO_SOURCE_UNPROCESSED).
13
14*    [C-1-2] MUST exhibit approximately flat amplitude-versus-frequency
15characteristics in the mid-frequency range: specifically ±10dB from
16100 Hz to 7000 Hz for each and every microphone used to record the unprocessed
17audio source.
18
19*    [C-1-3] MUST exhibit amplitude levels in the low frequency
20range: specifically from ±20 dB from 5 Hz to 100 Hz compared to the
21mid-frequency range for each and every microphone used to record the
22unprocessed audio source.
23
24*    [C-1-4] MUST exhibit amplitude levels in the high frequency
25range: specifically from ±30 dB from 7000 Hz to 22 KHz compared to the
26mid-frequency range for each and every microphone used to record the
27unprocessed audio source.
28
29*    [C-1-5] MUST set audio input sensitivity such that a 1000 Hz sinusoidal
30tone source played at 94 dB Sound Pressure Level (SPL) yields a response with
31RMS of 520 for 16 bit-samples (or -36 dB Full Scale for floating point/double
32precision samples) for each and every microphone used to record the unprocessed
33audio source.
34
35*    [C-1-6] MUST have a signal-to-noise ratio (SNR) at 60 dB or higher for
36each and every microphone used to record the unprocessed audio source.
37(whereas the SNR is measured as the difference between 94 dB SPL and equivalent
38SPL of self noise, A-weighted).
39
40*    [C-1-7] MUST have a total harmonic distortion (THD) less than be less than
411% for 1 kHZ at 90 dB SPL input level at each and every microphone used to
42record the unprocessed audio source.
43
44*    MUST not have any other signal processing (e.g. Automatic Gain Control,
45High Pass Filter, or Echo cancellation) in the path other than a level
46multiplier to bring the level to desired range. In other words:
47*    [C-1-8] If any signal processing is present in the architecture for any
48reason, it MUST be disabled and effectively introduce zero delay or extra
49latency to the signal path.
50*    [C-1-9] The level multiplier, while allowed to be on the path, MUST NOT
51introduce delay or latency to the signal path.
52
53All SPL measurements are made directly next to the microphone under test.
54For multiple microphone configurations, these requirements apply to
55each microphone.
56
57If device implementations declare `android.hardware.microphone` but do not
58support unprocessed audio source, they:
59
60*    [C-2-1] MUST return `null` for the `AudioManager.getProperty(PROPERTY_SUPPORT_AUDIO_SOURCE_UNPROCESSED)`
61API method, to properly indicate the lack of support.
62*    [SR] are still STRONGLY RECOMMENDED to satisfy as many of the requirements
63for the signal path for the unprocessed recording source.
64