We've been offering audio recording for a while, but our audio recorder was saving audio in 8KHz, since it's the most used format in good old telephony and when we have calls to/from PSTN. When we work with VoIP endpoints that do support wideband audio (WebRTC, SIP, mobile SDKs) we can save audio with much better quality without downsampling it to 8KHz. We chose 48 KHz as the base sample rate for HD audio recorder, since WebRTC/Opus can offer this quality, audio from endpoints with lower sample rate will be re-sampled.
It's easy to use HD audio recording, just add hd_audio parameter in the recorder params:
// Example for the record method of the Call class function
call.record({hd_audio: true});
// Example for the Recorder class
require(Modules.Recorder);
// ...
const recorder = VoxEngine.createRecorder({hd_audio: true});
call.sendMediaTo(recorder);
You can also use the lossless parameter, which is mutually exclusive with hd_audio. If lossless is set to true, audio will be recorded in the "Flac" format.