Convert Apple Lossless Audio Codec (.alac) to Advanced Audio Coding (.aac) online for free. Fast, secure audio conversion with no watermarks or registration.
Conversion settings — add a file to adjust
Upload your .m4a file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .aac file when it's ready.
ALAC (Apple Lossless Audio Codec) stores bit-perfect audio in M4A containers, achieving roughly 50% compression compared to raw PCM while preserving every sample. AAC (Advanced Audio Coding) is the industry-standard lossy codec, delivering transparent quality at 256 kbps with 10:1 compression ratios. Both ALAC and AAC live in the M4A container — they share the same file format, metadata system, and Apple ecosystem integration.
Converting ALAC to AAC trades lossless quality for dramatically smaller file sizes while remaining within the same M4A container ecosystem. This is the standard workflow for creating distribution copies from lossless masters on Apple platforms.
ALAC files at CD quality occupy roughly 5-6 MB per minute, while AAC at 256 kbps needs only about 2 MB per minute — a 60-70% size reduction with virtually indistinguishable quality. For mobile devices with limited storage, portable music players, and streaming, AAC provides the practical balance of quality and size.
Since both codecs share the M4A container, all metadata — album art, lyrics, chapter markers, iTunes tags, and library organization — transfers perfectly with zero mapping issues. This makes ALAC-to-AAC the smoothest possible lossy conversion within the Apple ecosystem.
FFmpeg decodes ALAC to PCM (lossless — no quality loss in this step) and encodes using the AAC encoder. Since both formats share the M4A container (MPEG-4 Part 14), the container structure, metadata, and album art are preserved directly. The AAC encoder applies MDCT and psychoacoustic modeling to the perfect PCM input. This single-generation lossy encode from a lossless source produces the best possible AAC quality. The covr (cover art) atom transfers without re-encoding.
At 256 kbps AAC-LC, the output is virtually indistinguishable from the ALAC original in blind listening tests — this is considered transparent quality. At 192 kbps, subtle differences may appear on high-end equipment. At 128 kbps, AAC still sounds excellent for casual listening. Since the encode starts from lossless PCM, the AAC output achieves the best possible quality for the chosen bitrate — no generation loss from a previous lossy step.
| Device | ALAC | AAC |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Native | Native |
| iPhone/iPad | Native | Native |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No |
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Resolution: N/A
Bitrate: 256 kbps
AAC format required
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
ALAC to AAC is the ideal lossy distribution workflow within the Apple ecosystem. Perfect PCM source, shared M4A container, and seamless metadata transfer produce the best possible AAC output.
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| No |
| 特性 | ALAC | AAC |
|---|---|---|
| 全称 | Apple Lossless Audio Codec | Advanced Audio Coding |
| 扩展名 | .m4a | .aac |
| 最适合 | Lossless | Superior to MP3 |