Convert Opus to AMR — Free Online Converter

AMR (Adaptive Multi-Rate) is the voice codec that powered billions of mobile phone calls during the 2G and 3G era. Developed by Ericsson and standardized by 3GPP, AMR-NB operates at 8 kHz with bitrates from 4.75 to 12.2 kbps, producing the characteristic "telephone voice" sound. Converting Opus — the state-of-the-art codec from Xiph.org that handles everything from 6 kbps narrowband to 510 kbps full-bandwidth stereo — to AMR sacrifices nearly all audio quality in exchange for compatibility with the oldest mobile telephony infrastructure.

This conversion makes sense only in specific telecommunications scenarios: feeding audio into IVR (Interactive Voice Response) systems, testing mobile network voice paths, or creating ringtones for ultra-basic feature phones. The output is tiny (under 100 KB per minute) but limited to telephone-grade 300-3400 Hz bandwidth.

AMR is the required input format for many telecom testing tools, IVR platforms, and voice quality assessment systems built for 2G/3G networks. If you have Opus recordings from modern VoIP systems and need to compare them against mobile network quality benchmarks, AMR is the standard reference format. Certain carrier-grade voice quality monitoring tools from Rohde & Schwarz, JDSU, and Spirent accept only raw AMR input.

Basic feature phones from manufacturers like Nokia, Samsung, and Itel still being sold in developing markets play AMR natively but lack codecs for Opus, MP3, or even AAC. For humanitarian organizations distributing audio content via basic phones, AMR is often the only viable format. The extremely small file sizes (under 100 KB per minute) also make AMR practical for distribution over 2G networks with severe bandwidth constraints.