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You're listening to a voice call on WhatsApp, Discord, or Zoom. The audio codec is almost certainly Opus. Designed from the ground up for both voice and music, Opus delivers remarkable quality at bitrates that would make MP3 sound like a tin can phone — voice calls at 32 kbps sound natural, and music at 128 kbps rivals MP3 at 192 kbps.
Opus was standardised by the IETF in 2012, combining technology from Skype's SILK codec (voice) and Xiph.org's CELT codec (music). It switches between them seamlessly depending on the content. The format is royalty-free, open-source, and technically superior to every proprietary alternative — which is why virtually every VoIP application adopted it. Firefox and Chrome play Opus natively in the browser.
VLC plays .opus files on every platform. Firefox and Chrome handle Opus in web audio. For converting Opus to MP3 (for older devices that don't support it), <a href="https://fwip.app/tools/opus-to-mp3/">fwip</a> handles it in the browser. If you're encoding audio for web streaming or voice applications, Opus at 96–128 kbps is the best quality-per-bit available today.
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