Google now has a standard for low-latency devices:
> 5.4. Audio Latency
> Audio latency is broadly defined as the interval between when an application requests an audio playback or record
operation, and when the device implementation actually begins the operation. Many classes of applications rely on
short latencies, to achieve real-time effects such sound effects or VOIP communication. Device implementations
that include microphone hardware and declare android.hardware.microphone SHOULD meet all audio latency
requirements outlined in this section. See Section 7 for details on the conditions under which microphone hardware
may be omitted by device implementations.
> For the purposes of this section:
> - "cold output latency" is defined to be the interval between when an application requests audio playback and
when sound begins playing, when the audio system has been idle and powered down prior to the request
> - "warm output latency" is defined to be the interval between when an application requests audio playback and
when sound begins playing, when the audio system has been recently used but is currently idle (that is, silent)
> - "continuous output latency" is defined to be the interval between when an application issues a sample to be
played and when the speaker physically plays the corresponding sound, while the device is currently playing
back audio
> - "cold input latency" is defined to be the interval between when an application requests audio recording and
when the first sample is delivered to the application via its callback, when the audio system and microphone
has been idle and powered down prior to the request
> - "continuous input latency" is defined to be when an ambient sound occurs and when the sample
corresponding to that sound is delivered to a recording application via its callback, while the device is in
recording mode
> Using the above definitions, device implementations SHOULD exhibit each of these properties:
> - cold output latency of 100 milliseconds or less
> - warm output latency of 10 milliseconds or less
> - continuous output latency of 45 milliseconds or less
> - cold input latency of 100 milliseconds or less
> - continuous input latency of 50 milliseconds or less
> Note: while the requirements outlined above are stated as "SHOULD" for Android 4.1, the Compatibility Definition
for a future version is planned to change these to "MUST". That is, these requirements are optional in Android 4.1
but will be required by a future version. Existing and new devices that run Android 4.1 are very strongly
encouraged to meet these requirements in Android 4.1, or they will not be able to attain Android compatibility
when upgraded to the future version.
> If a device implementation meets the requirements of this section, it MAY report support for low-latency audio, by
reporting the feature "android.hardware.audio.low-latency" via the android.content.pm.PackageManager class.
[Resources, 37] Conversely, if the device implementation does not meet these requirements it MUST NOT report
support for low-latency audio.