This post is short and simple: your mp3 or ogg files played on VoxEngine scenario level with call.startPlayback or using Player will be played on the Web or Mobile SDK side in HD quality (48KHz), or on SIP side if it does support wideband audio codecs (Speex or Opus). It also appeared that Opus has 3 encoding presets - auto / speech / music, currently we use auto, but maybe we will let developers decide which preset can be used on VoxEngine scenario level later.
The Ultimate Guide to Call Tracking: Benefits and Implementation with Voximplant
Call tracking is a powerful tool to analyze and optimize phone interactions with customers. Let's explore the many benefits of call tracking and how it can help businesses of all sizes.