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AU at a glance
AU
AU belongs to an earlier multimedia era where workstation and Unix vendors often had their own practical audio defaults.
AAC at a glance
AAC
AAC emerged from MPEG's work on a more capable audio codec family after MP3, and Fraunhofer IIS remains one of the organizations most closely associated with its development and deployment.
Format comparison
| Feature | AU | AAC |
|---|---|---|
| File type | Audio | Audio |
| Extensions |
|
|
| MIME type |
|
|
| Created year | 1987 | 1997 |
| Inventor | Sun Microsystems | MPEG |
| Status | active | proprietary |
| Primary use cases |
|
|
| Multitrack support | Not supported | Not supported |
| HDR support | Not supported | Not supported |
| Streaming ready | Not supported | Supported |
When to use each format
When to use AU
- Your source file is already in AU.
- Preserve source expectations before exporting to AAC.
- AU is commonly used in audio workflows.
When to use AAC
- Your target workflow expects AAC.
- Improve delivery compatibility with AAC.
- AAC is commonly used in audio workflows.
FAQs
Why convert AU to AAC?
AAC conversion is essential when targeting Apple's ecosystem or streaming platforms.
Convert to AAC when creating podcasts, music streams, or audio for YouTube.
If your workflow includes iTunes integration or requires maximum compatibility with mobile devices, AAC is the practical choice.
Video producers frequently convert audio to AAC when working with MP4 video containers, since MP4s typically pair with AAC audio for optimal streaming compatibility.
AAC offers significantly better quality-per-bitrate than MP3 while maintaining broad compatibility.
Choose AAC when you need smaller file sizes than lossless formats but better audio quality than MP3 at equivalent bitrates.
What changes when converting AU to AAC?
This conversion changes how the format behaves in downstream tools and delivery environments.
Moving to AAC adds streaming delivery.
What should I review after converting AU to AAC?
Validate output quality on representative files and confirm the target format behaves correctly in the destination workflow.