Convert FLAC to AMR — Free Online Converter
Convert Free Lossless Audio Codec (.flac) to Adaptive Multi-Rate Audio (.amr) online for free. Fast, secure audio conversion with no watermarks or reg...
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Upload your .flac file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .amr file when it's ready.
About FLAC to AMR Conversion
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.
Why Convert FLAC to AMR?
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.
Common Use Cases
- Creating voice prompts for IVR systems on legacy PBX hardware
- Preparing voicemail greetings for GSM-based corporate phone systems
- Generating ultra-compact audio clips for SMS gateway integrations
- Encoding narration files for embedded devices with limited codec support
- Testing audio playback on feature phones that only decode AMR
How It Works
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.
Quality & Performance
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 Compatibility
| Device | FLAC | AMR |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Native | Partial |
| Linux | Partial | Partial |
| Web Browser | No | No |
Recommended Settings by Platform
Spotify
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Apple Music
Resolution: N/A
Bitrate: 256 kbps
AAC format required
SoundCloud
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Podcast
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
Tips for Best Results
- 1Always use 12.2 kbps (the highest AMR-NB mode) unless your target system explicitly requires a lower rate
- 2Pre-process FLAC with a high-pass filter at 300 Hz and low-pass at 3400 Hz to match AMR-NB's passband before encoding
- 3For better speech quality, target AMR-WB if the receiving system supports it
- 4Normalize audio levels before conversion — AMR's narrow dynamic range benefits from consistent input levels
Related Conversions
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.