Convert MP4 to AMR — Free Online Converter

MP4 to AMR conversion extracts the audio track from an MPEG-4 video and encodes it in Adaptive Multi-Rate format. AMR was developed by the European Telecommunications Standards Institute (ETSI) specifically for cellular voice calls over GSM and 3G networks. It operates at extremely low bitrates (4.75 to 12.2 kbps) and is optimized for human speech rather than music or general audio.

Our converter decodes the MP4 audio and re-encodes it using the AMR-NB (Narrowband) codec at 8 kHz mono. The resulting file is tiny — a 10-minute recording produces an AMR file under 1 MB.

AMR conversion makes sense when you need to extract voice content from video for telephony applications, voice messaging systems, or legacy mobile platforms. Many older VoIP systems, IVR (Interactive Voice Response) systems, and cellular voicemail platforms use AMR as their native format. If you are building content for distribution on 2G/3G networks where bandwidth is precious, AMR's extreme compression is unmatched. The format excels at speech intelligibility even at its lowest 4.75 kbps rate.

FFmpeg decodes the MP4 audio stream and re-encodes using the libopencore-amrnb encoder. The output is 8 kHz mono (narrowband), which is the AMR-NB standard. Bitrate options range from 4.75 to 12.2 kbps, with 12.2 kbps (Mode 7) providing the best speech quality. The AMR container stores frames of 20 ms each. For wideband speech, AMR-WB (16 kHz, up to 23.85 kbps) can be selected using the libopencore-amrwb encoder.