Convert FLAC to AMR: Free Online Converter
Convert Free Lossless Audio Codec to Adaptive Multi-Rate Audio online for free. Fast, secure audio conversion with no watermarks or registration.
FLACに対応
アップロードすることで、これらのファイルの権利を有していること、および利用規約に同意することを確認したものとみなされます。
変換設定: ファイルを追加すると調整できます
安全な転送
HTTPS暗号化アップロード
プライバシー優先
ゲストのファイルは約2時間で自動削除
登録不要
すぐに変換を開始
どこでも動作
あらゆるブラウザ、あらゆるデバイス
FLAC から AMR への設定
- エンジン
- メディア
- 設定
- 調整できる設定: 9
- Trim Start
- Trim End
- Volume
- Fade In
- Fade Out
- Bitrate
- Audio Channels
- Reverse Audio
- Strip Metadata
変換方法
アップロードエリアにドラッグするか、クリックして選択し、.flacファイルをアップロードしてください。
必要に応じて出力設定を調整してください。デフォルト設定ではオリジナルの品質を維持します。
「変換」をクリックし、準備ができたら.amrファイルをダウンロードしてください。
FLACからAMRへの変換について
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.
FLACをAMRに変換する理由
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.
主な活用例
- 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
仕組み
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.
品質とパフォーマンス
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.
デバイス互換性
| Device | FLAC | AMR |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Native | Partial |
| Linux | Partial | Partial |
| Web Browser | No | No |
プラットフォーム別の推奨設定
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
最良の結果を得るためのヒント
- 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
関連する変換
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.
FLACとAMRの比較
| 特徴 | FLAC | AMR |
|---|---|---|
| 正式名称 | Free Lossless Audio Codec | Adaptive Multi-Rate Audio |
| 拡張子 | .flac | .amr |