1## 5.10\. Professional Audio 2 3If device implementations report support for feature 4`android.hardware.audio.pro` via the 5[android.content.pm.PackageManager]( 6http://developer.android.com/reference/android/content/pm/PackageManager.html) 7class, they: 8 9* [C-1-1] MUST report support for feature 10`android.hardware.audio.low_latency`. 11* [C-1-2] MUST have the continuous round-trip audio latency, as defined in 12[section 5.6 Audio Latency](#5_6_audio_latency), MUST be 20 milliseconds or less and SHOULD be 1310 milliseconds or less over at least one supported path. 14* [C-1-3] MUST include a USB port(s) supporting USB host mode and USB 15peripheral mode. 16* [C-1-4] MUST report support for feature `android.software.midi`. 17* [C-1-5] MUST meet latencies and USB audio requirements using both the 18[OpenSL ES](https://developer.android.com/ndk/guides/audio/opensl-for-android.html) 19PCM buffer queue API and at least one path of the [AAudio native audio](https://developer.android.com/ndk/guides/audio/aaudio/aaudio.html) 20API. 21* [SR] Are STRONGLY RECOMMENDED to meet latencies and USB audio requirements 22using the [AAudio native audio](https://developer.android.com/ndk/guides/audio/aaudio/aaudio.html) 23API over the [MMAP path](https://source.android.com/devices/audio/aaudio). 24* [C-1-6] MUST have Cold output latency of 200 milliseconds or less. 25* [C-1-7] MUST have Cold input latency of 200 milliseconds or less. 26* [SR] Are STRONGLY RECOMMENDED to provide a consistent level of CPU 27performance while audio is active and CPU load is varying. This should be tested 28using the Android app version of [SynthMark](https://github.com/google/synthmark) 29commit id [09b13c6f49ea089f8c31e5d035f912cc405b7ab8](https://github.com/google/synthmark/commit/09b13c6f49ea089f8c31e5d035f912cc405b7ab8). 30SynthMark uses a software synthesizer running on a simulated audio framework 31that measures system performance. The SynthMark app needs to be run using the 32“Automated Test” option and achieve the following results: 33 * voicemark.90 >= 32 voices 34 * latencymark.fixed.little <= 15 msec 35 * latencymark.dynamic.little <= 50 msec 36 37See the SynthMark [documentation](https://github.com/google/synthmark/blob/master/docs/README.md) 38for an explanation of the benchmarks. 39 40* SHOULD minimize audio clock inaccuracy and drift relative to standard time. 41* SHOULD minimize audio clock drift relative to the CPU `CLOCK_MONOTONIC` 42when both are active. 43* SHOULD minimize audio latency over on-device transducers. 44* SHOULD minimize audio latency over USB digital audio. 45* SHOULD document audio latency measurements over all paths. 46* SHOULD minimize jitter in audio buffer completion callback entry times, as this 47affects usable percentage of full CPU bandwidth by the callback. 48* SHOULD provide zero audio glitches under normal use at reported latency. 49* SHOULD provide zero inter-channel latency difference. 50* SHOULD minimize MIDI mean latency over all transports. 51* SHOULD minimize MIDI latency variability under load (jitter) over all transports. 52* SHOULD provide accurate MIDI timestamps over all transports. 53* SHOULD minimize audio signal noise over on-device transducers, including the 54period immediately after cold start. 55* SHOULD provide zero audio clock difference between the input and output sides of 56corresponding end-points, when both are active. Examples of corresponding 57end-points include the on-device microphone and speaker, or the audio jack input 58and output. 59* SHOULD handle audio buffer completion callbacks for the input and output sides 60of corresponding end-points on the same thread when both are active, and enter 61the output callback immediately after the return from the input callback. Or 62if it is not feasible to handle the callbacks on the same thread, then enter the 63output callback shortly after entering the input callback to permit the 64application to have a consistent timing of the input and output sides. 65* SHOULD minimize the phase difference between HAL audio buffering for the input 66and output sides of corresponding end-points. 67* SHOULD minimize touch latency. 68* SHOULD minimize touch latency variability under load (jitter). 69* SHOULD have a latency from touch input to audio output of less than or 70equal to 40 ms. 71 72If device implementations meet all of the above requirements, they: 73 74* [SR] STRONGLY RECOMMENDED to report support for feature 75`android.hardware.audio.pro` via the [`android.content.pm.PackageManager`]( 76http://developer.android.com/reference/android/content/pm/PackageManager.html) 77class. 78 79If device implementations include a 4 conductor 3.5mm audio jack, they: 80 81* [C-2-1] MUST have the continuous round-trip audio latency to be 20 82milliseconds or less over the audio jack path. 83* [SR] STRONGLY RECOMMENDED to comply with 84section [Mobile device (jack) specifications]( 85https://source.android.com/devices/accessories/headset/jack-headset-spec) 86of the [Wired Audio Headset Specification (v1.1)]( 87https://source.android.com/devices/accessories/headset/plug-headset-spec). 88* The continuous round-trip audio latency SHOULD be 10 milliseconds 89or less over the audio jack path. 90 91If device implementations omit a 4 conductor 3.5mm audio jack and 92include a USB port(s) supporting USB host mode, they: 93 94* [C-3-1] MUST implement the USB audio class. 95* [C-3-2] MUST have a continuous round-trip audio latency of 20 96milliseconds or less over the USB host mode port using USB audio class. 97* The continuous round-trip audio latency SHOULD be 10 milliseconds 98or less over the USB host mode port using USB audio class. 99* [C-SR] Are STRONGLY RECOMMENDED to support simultaneous I/O up to 8 channels 100 each direction, 96 kHz sample rate, and 24-bit or 32-bit depth, when used 101 with USB audio peripherals that also support these requirements. 102 103If device implementations include an HDMI port, they: 104 105* SHOULD support output in stereo and eight channels at 20-bit or 10624-bit depth and 192 kHz without bit-depth loss or resampling, 107in at least one configuration. 108