AU vs M4A
Um comparativo detalhado de Sun AU Audio e M4A Audio — tamanho de arquivo, qualidade, compatibilidade e qual escolher de acordo com seu fluxo de trabalho.
Sun AU Audio
Audio FilesAU is a simple audio format from Sun Microsystems, commonly used on Unix systems.
Sobre os arquivos AUM4A Audio
Audio FilesM4A is an MPEG-4 audio container typically containing AAC or ALAC encoded audio. It is the standard format for iTunes purchases and Apple Music downloads.
Sobre os arquivos M4AComparativo de vantagens
AU Vantagens
- Trivially simple format — 24-byte header, then samples.
- µ-law 8-bit variant fits hours of speech in kilobytes.
- Stable since 1988; every major audio library reads it.
- Streaming-friendly: size field is optional.
M4A Vantagens
- Superior audio quality to MP3 at the same bitrate (AAC codec).
- Native support across Apple, iOS, Android, and Windows.
- Carries rich metadata: album art, chapters, lyrics, podcast bookmarks.
- Same container as MP4 — tooling overlaps with video workflows.
- Lossless variant (ALAC inside M4A) for audiophile archiving.
Limitações
AU Limitações
- Aging — obsolete outside legacy and compatibility scenarios.
- No metadata beyond a single annotation string.
- No native multi-channel surround support.
- Limited to 8 codecs, none modern.
M4A Limitações
- AAC patents still active in some jurisdictions — licensing fees apply for encoders.
- Seeking in variable-bitrate M4As can drift without an index atom.
- Less universal than MP3 on older hardware (pre-2010 car stereos, cheap MP3 players).
- Container overhead is larger than a raw ADTS AAC stream.
Especificações técnicas
| Especificação | AU | M4A |
|---|---|---|
| MIME types | audio/basic, audio/au, audio/x-au | — |
| Extensions | .au, .snd | — |
| Header | 24 bytes (magic, offset, size, encoding, rate, channels, info) | — |
| Codecs | PCM 8/16/24/32-bit, µ-law, A-law, IEEE float | AAC-LC, HE-AAC, ALAC |
| Byte order | Big-endian | — |
| MIME type | — | audio/mp4 |
| Extension | — | .m4a (and .m4b for audiobooks, .m4p for legacy DRM) |
| Container | — | ISO Base Media File Format (ISOBMFF) |
| Max sample rate | — | 96 kHz |
Tamanhos típicos de arquivo
AU
- 10-second clip (8-bit µ-law, 8 kHz) 80 KB
- 10-second clip (16-bit PCM, 44.1 kHz stereo) ~1.7 MB
M4A
- 4-minute song (AAC 128 kbps) 4-5 MB
- 4-minute song (AAC 256 kbps) 8-10 MB
- 1-hour podcast (64 kbps) 28 MB
- 4-minute song (Apple Lossless) 25-35 MB
Pronto para converter?
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Perguntas frequentes
AU (Sun AU Audio) is an audio file format used to store sound recordings — music, voice, podcasts, sound effects. The format defines how the audio samples are compressed (or stored raw), what bitrates are supported, and how metadata such as title, artist, album, and cover art is embedded. It is part of the audio files family.
AU (Sun AU Audio) is an audio formatoo de arquivo used to store sound recordings — music, voice, podcasts, sound effects. The formato defines how the audio samples are comprimido (or stored raw), what bitrates are suportado, e how metadata como title, artist, album, e cover art is embedded. It is part of the audio arquivos family.
VLC, foobar2000, and the default media players on Windows and macOS handle AU natively. On mobile, iOS Music and Android media apps vary in their support — popular formats work everywhere; niche ones may need a dedicated app. If playback fails on a device, converting to MP3 or AAC usually solves it.
VLC, foobar2000, e the default media players no Windows e macOS handle AU natively. On mobile, iOS Music e Android media apps vary in their support — popular formatoos funcionar everywhere; niche ones may need a dedicated app. If playback fails em um device, convertendo to MP3 ou AAC Geralmente solves it.
Upload the AU to KaijuConverter and pick MP3, WAV, FLAC, AAC, OGG, or any other target. Our FFmpeg pipeline decodes the audio and re-encodes to the target format at sensible default bitrates (VBR ~190 kbps for music, 96 kbps for speech). Metadata and cover art travel with the audio where both formats support them.
AU can be lossy or lossless depending on the specific variant. Lossy variants (smaller files) discard some audio detail during compression in ways tuned to be inaudible; lossless variants preserve every sample exactly but produce larger files. For distribution, lossy at high bitrate is standard; for archival, lossless wins.