Convert FLV to AMR — Free Online Converter

FLV (Flash Video) uses MP3 or AAC for its audio track at typical bitrates of 96-320 kbps. AMR (Adaptive Multi-Rate) is a speech-optimized codec standardized by 3GPP and ETSI, operating at bitrates from 4.75 to 12.2 kbps. AMR was designed for cellular voice communication and is the default voice recording format on many Android phones and Nokia devices. Converting FLV to AMR produces extremely compact audio files optimized for intelligible speech at minimal file sizes.

AMR excels at speech compression, achieving intelligible voice at just 4.75 kbps — roughly 1/25th the size of a typical MP3. If you need to extract spoken content from FLV recordings (lectures, interviews, phone calls) and file size is critical, AMR delivers the smallest possible files while keeping speech understandable. It is also required for MMS voice messages on many mobile networks.

FFmpeg decodes the FLV audio stream to PCM, resamples to 8 kHz mono (AMR-NB requirement), and encodes using the libopencore-amrnb encoder. AMR uses ACELP (Algebraic Code-Excited Linear Prediction) to model speech characteristics efficiently. The output is wrapped in a standard AMR file with the '#!AMR ' magic header. AMR-WB (wideband, 16 kHz) is also available for better speech quality at 6.6-23.85 kbps.