Convert Opus to 3GP — Free Online Converter

Opus is the most technically advanced audio codec available today, developed jointly by Xiph.org and the IETF and standardized as RFC 6716 in 2012. It uniquely combines two compression technologies — SILK (originally created for Skype voice calls) and CELT (a low-latency music codec) — allowing it to adaptively switch between speech and music modes within a single stream. Converting Opus to 3GP repackages this audio into the 3GPP multimedia container designed for mobile networks, making it playable on legacy handsets that predate Opus support entirely.

The 3GP format was the standard multimedia container for 2G and 3G mobile phones, using AMR or AAC audio codecs internally. Since 3GP does not natively carry Opus streams, this conversion requires transcoding the audio from Opus to AMR-NB, which is the codec embedded inside the 3GP container. The result is a file that plays on virtually any mobile phone manufactured in the last twenty years, including basic feature phones from Nokia, Samsung, and Motorola.

Opus files cannot play on older mobile phones or feature phones because these devices lack an Opus decoder. The 3GP format, however, is universally supported across billions of legacy handsets worldwide. If you have Opus recordings from Discord calls, WebRTC sessions, or WhatsApp voice messages and need to play them on a basic phone, 3GP is one of the few formats guaranteed to work.

Additionally, some MMS (Multimedia Messaging Service) gateways only accept 3GP attachments. If you need to send audio via MMS on a carrier that enforces format restrictions, converting from Opus to 3GP ensures delivery. The conversion also serves telecom professionals who test voice quality across different network generations and need standardized 3GP test files.

FFmpeg decodes the Opus stream (which may operate at anywhere from 6 kbps to 510 kbps with a 48 kHz internal sample rate) and re-encodes it using the AMR-NB codec at 8 kHz sample rate with bitrates between 4.75 and 12.2 kbps inside a 3GP container. The dramatic reduction from Opus's full-bandwidth audio to AMR's 300-3400 Hz telephone bandwidth is unavoidable because 3GP targets legacy mobile hardware. The encoding uses the libopencore-amrnb library.