Cobalt enables voice search through a subset of the MediaRecorder Web API
In order to check whether to enable voice control or not, web apps will call the MediaDevices.enumerateDevices() Web API function within which Cobalt will in turn call a subset of the Starboard SbMicrophone API.
Partners can add microphone support and microphone gesture options using the optional SoftMicPlatformService, detailed below.
To enable the MediaRecorder API in Cobalt, the complete SbMicrophone API must be implemented.
Web applications are expected to use the MediaRecorder API. This in turn relies on the SbMicrophone API as detailed above.
In starboard/linux/shared/soft_mic_platform_service.cc there is an example stub implementation of the SoftMicPlatformService. Platforms can optionally implement this CobaltPlatformService to specify if they support the soft mic and/or hard mic for voice search. The soft mic refers to the software activation of the microphone for voice search through the UI microphone button on the Youtube Web Application search page. The hard mic refers to hardware button activation of the microphone for voice search. Platforms can also specify the optional micGesture. This specifies the type of UI prompt the YouTube Web Application should display to guide the user to start voice search. The options include an empty or null value for no prompt, "TAP" for tap the soft mic and/or hard mic to start voice search, or "HOLD" for hold the soft mic and/or the hard mic to start voice search.
The Web Application messages to the platform will be singular strings, encoded with enclosing quotation marks to make them JSON compliant:
"\"notifySearchActive\"" "\"notifySearchInactive\""
These messages notify the platform when the user is entering or exiting the Youtube Web Application search page. Only a synchronous true or false response is sent from the platform to confirm that the message was correctly received and parsed.
"\"getMicSupport\""
A similar synchronous true or false response is sent from the platform confirming the message was correctly received and parsed. The platform will also send an asynchronous string encoded JSON object with the above mentioned microphone preferences:
"{
'hasHardMicSupport' : boolean,
'hasSoftMicSupport' : boolean,
'micGesture' : string,
}"