Convert Free Lossless Audio Codec (.flac) to Adaptive Multi-Rate Audio (.amr) online for free. Fast, secure audio conversion with no watermarks or registration.
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AMR (Adaptive Multi-Rate) is a narrowband speech codec standardized by 3GPP, operating at bitrates between 4.75 and 12.2 kbps. It was the backbone of GSM and 3G voice calls for over a decade. Converting FLAC to AMR is a dramatic compression — from lossless CD-quality audio down to telephone-grade speech encoding. This conversion only makes sense for very specific scenarios involving legacy telephony systems, feature phones, or embedded devices that require AMR input.
AMR remains the mandatory speech codec for GSM networks and many VoIP gateways. Certain IVR (Interactive Voice Response) systems, automated calling platforms, and legacy voicemail systems accept only AMR-encoded audio. Converting FLAC recordings of voice prompts, announcements, or instructional content into AMR ensures compatibility with these older but still-operational telephony infrastructures.
FFmpeg decodes the FLAC to PCM, resamples to 8 kHz mono (AMR-NB's required input format), and encodes via libopencore-amrnb. AMR-NB uses Algebraic Code-Excited Linear Prediction (ACELP) — a speech-optimized model that assumes the signal is human voice. Eight codec modes exist, from 4.75 kbps to 12.2 kbps. The AMR-WB (Wideband) variant operates at 16 kHz with 6.6-23.85 kbps, providing FM-radio-like voice quality. The output is a raw .amr file with the standard `#!AMR\n` header.
AMR-NB at 12.2 kbps produces telephone-quality speech (300-3400 Hz bandwidth). Music is essentially destroyed — only the fundamental pitch and basic harmonic structure of voices survive. AMR-WB at 23.85 kbps is significantly better for speech clarity but still unsuitable for music. This conversion is a one-way trip: converting AMR back to FLAC restores no lost information.
| Device | FLAC | AMR |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Native | Partial |
| Linux | Partial | Partial |
| Web Browser | No |
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Resolution: N/A
Bitrate: 256 kbps
AAC format required
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
FLAC to AMR is appropriate exclusively for speech-oriented content destined for legacy telephony systems. Always use the highest AMR bitrate your target system supports, and never use this conversion for music.
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Mọi trình duyệt, mọi thiết bị
| No |
| Tính năng | FLAC | AMR |
|---|---|---|
| Tên đầy đủ | Free Lossless Audio Codec | Adaptive Multi-Rate Audio |
| Phần mở rộng | .flac | .amr |
| Phù hợp nhất cho | Lossless compression | Speech optimized |