OPUS to AU — Format Comparison & Online Converter
Fast, instant OPUS to AU conversion. No signup required. Just drop your .opus file and get .au in seconds.
Batch Settings
日頃より、当ファイル変換サービスをご利用いただき、誠にありがとうございます。このページでは、高音質な音声圧縮フォーマットであるOPUSファイルを、幅広い環境で互換性のあるAU（μ-Law）形式へ変換する手順をご紹介します。特に、音声コンテンツの制作や共有において、互換性の問題に直面された経験をお持ちの方もいらっしゃるのではないでしょうか。AU形式は、その誕生から長い歴史を持つ信頼性の高いフォーマットであり、多種多様なOSや再生ソフトウェアで安定した動作が期待できます。変換プロセスは非常にシンプルで、どなたでも手軽にご利用いただけますので、ぜひお試しください。音源の特性を損なうことなく、より多くの環境でアクセス可能な形へと最適化することで、皆様のクリエイティブな活動やビジネスシーンにおけるコミュニケーションを力強くサポートいたします。
- アニメ・漫画の音声素材管理
- ビジネス会議録の共有
- 伝統芸能のデジタルアーカイブ化
AU形式は、特にUNIX系のシステムで広く利用されてきた歴史があり、一部の専門的な音響機器や旧来のシステムとの連携において、その互換性が重宝されることがあります。日本では、特定の音響研究機関や放送業界で、過去の資産との互換性維持のために利用されるケースも存在します。
About OPUS to AU Conversion
OPUS (introduced 2012) and AU are both audio formats, but they differ in important ways. Opus is a versatile open codec excelling at both speech and music, used in WebRTC and Discord. AU is a widely used file format.
When you convert OPUS to AU, the goal is to convert between formats quickly. Converting OPUS to AU maintains high quality with CocoConvert's optimised encoder settings. Understanding these technical differences helps you choose the right format for your workflow.
Your OPUS file is decoded and re-encoded as AU. The conversion involves 4 steps: (1) your opus file is uploaded and validated, (2) the file is decoded (parsed into its raw data), (3) the data is re-encoded in au format, (4) the converted file is ready for download.
CocoConvert's converter handles the entire pipeline server-side using FFmpeg, Sharp, and qpdf — battle-tested libraries used by streaming platforms and enterprise tools. Files are encrypted in transit and deleted within 24 hours.
This conversion is ideal when you When you need a AU file. For the opposite direction, CocoConvert also supports AU to OPUS conversion.
How to Convert OPUS to AU
- 1
Upload .opus file
Select your OPUS file by dragging it to the upload zone or using the file picker. Batch upload is available for multiple files.
- 2
Choose .au
Set AU as the output format. The converter uses optimal settings based on the OPUS→AU conversion profile.
- 3
Convert
The server-side engine decodes your OPUS file and re-encodes it as AU. Processing time depends on file size and complexity.
- 4
Download result
Grab your converted .au file. Multiple output files can be downloaded together.
What Happens When You Convert OPUS to AU
Your OPUS file is decoded and re-encoded as AU.
Your OPUS file is uploaded and validated
The file is decoded (parsed into its raw data)
The data is re-encoded in AU format
The converted file is ready for download
Format Comparison
Opus
.opus file
| Extension | .opus |
| MIME Type | audio/opus |
| Category | Audio |
AU
.au file
| Extension | .au |
| MIME Type | audio/basic |
| Category | Audio |
Should You Convert OPUS to AU?
When to Convert
- ✓When you need a AU file
Frequently Asked Questions
What is the difference between OPUS and AU?
Opus is a versatile open codec excelling at both speech and music, used in WebRTC and Discord. AU is a widely used file format.
Does OPUS to AU conversion affect quality?
Converting OPUS to AU maintains high quality with CocoConvert's optimised encoder settings.
Which format has better compression, OPUS or AU?
OPUS uses lossy compression. AU is widely supported. The better choice depends on whether you prioritize file size or quality.
How long does OPUS to AU conversion take?
Most conversions finish in seconds. Larger files or complex audio content may take 10–30 seconds. CocoConvert processes files in parallel for batch jobs.
Is OPUS or AU better for long-term storage?
Both formats use lossy compression, so consider keeping your original source file for long-term storage.
Versions are pinned in our worker Dockerfile and re-built via CI on every change.