Convert Opus to AMR: Free Online Converter
Convert Opus Audio Codec to Adaptive Multi-Rate Audio online for free. Fast, secure audio conversion with no watermarks or registration.
OPUS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
Opus 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、.opus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。
OpusからAMRへの変換について
AMR (Adaptive Multi-Rate) is the voice codec that powered billions of mobile phone calls during the 2G and 3G era. Developed by Ericsson and standardized by 3GPP, AMR-NB operates at 8 kHz with bitrates from 4.75 to 12.2 kbps, producing the characteristic "telephone voice" sound. Converting Opus, the state-of-the-art codec from Xiph.org that handles everything from 6 kbps narrowband to 510 kbps full-bandwidth stereo, to AMR sacrifices nearly all audio quality in exchange for compatibility with the oldest mobile telephony infrastructure.
This conversion makes sense only in specific telecommunications scenarios: feeding audio into IVR (Interactive Voice Response) systems, testing mobile network voice paths, or creating ringtones for ultra-basic feature phones. The output is tiny (under 100 KB per minute) but limited to telephone-grade 300-3400 Hz bandwidth.
OpusをAMRに変換する理由
AMR is the required input format for many telecom testing tools, IVR platforms, and voice quality assessment systems built for 2G/3G networks. If you have Opus recordings from modern VoIP systems and need to compare them against mobile network quality benchmarks, AMR is the standard reference format. Certain carrier-grade voice quality monitoring tools from Rohde & Schwarz, JDSU, and Spirent accept only raw AMR input.
Basic feature phones from manufacturers like Nokia, Samsung, and Itel still being sold in developing markets play AMR natively but lack codecs for Opus, MP3, or even AAC. For humanitarian organizations distributing audio content via basic phones, AMR is often the only viable format. The extremely small file sizes (under 100 KB per minute) also make AMR practical for distribution over 2G networks with severe bandwidth constraints.
主な活用例
- Feed VoIP recordings into telecom voice quality testing equipment
- Create test audio for IVR systems that only accept AMR input
- Produce audio files for basic feature phones in developing markets
- Generate minimal-size audio for distribution over 2G mobile networks
- Compare Opus voice quality against AMR baselines for codec evaluation
仕組み
FFmpeg decodes the Opus stream (48 kHz, up to 510 kbps) and re-encodes using libopencore-amrnb at 8 kHz sample rate. The AMR-NB codec operates in discrete modes with bitrates of 4.75, 5.15, 5.9, 6.7, 7.4, 7.95, 10.2, or 12.2 kbps. The default is 12.2 kbps (Mode 7), which offers the best AMR-NB quality. All audio above 3.4 kHz is discarded during the sample rate conversion from 48 kHz to 8 kHz. The output uses the simple AMR file format with a #!AMR\n header.
品質とパフォーマンス
Extreme quality reduction. Opus can encode full-bandwidth stereo audio at up to 510 kbps with a 48 kHz sample rate. AMR-NB is limited to 300-3400 Hz mono at 12.2 kbps maximum. Music becomes unrecognizable, environmental sounds disappear, and only clear speech remains intelligible. This is purely a compatibility-driven conversion.
デバイス互換性
| Device | Opus | AMR |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Partial | 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
- 1Only convert to AMR when the target device or system specifically requires it
- 2AMR files are among the smallest audio files possible — under 100 KB per minute
- 3For better mobile compatibility, consider AAC or MP3 instead of AMR
- 4The 12.2 kbps mode provides the best AMR-NB quality — avoid lower modes unless bandwidth is critical
- 5Speech remains intelligible in AMR, but do not expect any music or ambient sound to survive
関連する変換
Opus to AMR is a specialized conversion for telecom professionals, IVR systems, and feature phone distribution. The quality loss is severe but intentional — AMR exists for telephony compatibility, not audio fidelity. Use it only when the target system or device specifically requires AMR format.
OpusとAMRの比較
| 特徴 | Opus | AMR |
|---|---|---|
| 正式名称 | Opus Audio Codec | Adaptive Multi-Rate Audio |
| 拡張子 | .opus | .amr |