Convert M4A to AAC
Convert M4A files to raw AAC (.aac) format directly in your browser. Strips the MP4 container and produces an ADTS-framed AAC stream usable in HLS, Shoutcast, and embedded broadcast systems. No upload needed.
Drag 'n' drop files here, or
click to select files
.m4a
Drop your files and click Convert to get AAC
//when_to_use
When to Convert M4A to AAC
- Preparing M4A music for HLS streaming pipelines that segment ADTS-AAC chunks (Apple Live Streaming spec)
- Converting M4A archives to AAC for Shoutcast / Icecast Internet radio server playlists
- Extracting ADTS-AAC from M4A for upload to Axia / Telos broadcast automation hardware
- Generating raw AAC files for embedded car head units that don't recognize the .m4a extension
- Stripping iTunes metadata from M4A purchases to obtain bare AAC for archival
//comparison
M4A vs AAC
| Property | M4A | AAC |
|---|---|---|
| Container | MP4 (atom-based) | ADTS (stream) |
| Typical size (3 min) | 3-5 MB | 3-4.8 MB |
| Metadata | Atoms (title, artist, cover) | None (raw stream) |
| Re-encoding | — | None (lossless extraction) |
| Use case | iTunes, iPhone, file playback | HLS, Shoutcast, broadcast |
| Conversion type | — | Stream copy (instant) |
//how_it_works
How It Works
Drop your M4A files
Drag and drop or select M4A files. First conversion loads FFmpeg WASM (~30MB).
FFmpeg demuxes the MP4
FFmpeg WASM walks the MP4 atom hierarchy and extracts AAC packets from the mdat atom — no decoding.
ADTS reframing
Each AAC frame is wrapped in a 7-byte ADTS sync header (sample rate, channel config, profile) producing a standalone .aac stream.
Download AAC files
Resulting .aac files are ready for HLS, Shoutcast, broadcast hardware, or embedded player ingestion.
// under the hood
M4A is an ISO Base Media File Format (MP4) container with AAC audio in mdat atoms and metadata in moov atoms. Raw AAC (.aac) is the same AAC bitstream framed with ADTS sync words. Our converter uses FFmpeg WASM with -c:a copy to demux the M4A and re-frame the AAC packets as ADTS without decode/re-encode — the audio data is byte-identical.
//faq
Frequently Asked Questions
- Aren't M4A and AAC the same thing?
- Almost — but not quite. M4A is an MP4 container holding an AAC audio track (with metadata atoms, chapter markers, cover art). A bare .aac file is the AAC bitstream framed in ADTS (Audio Data Transport Stream) headers, with no container. Many broadcast and streaming systems require ADTS, not MP4.
- Does this re-encode the audio?
- No — this is a stream copy. The AAC packets inside the M4A are extracted and re-framed in ADTS headers without decoding. Audio quality is bit-identical to the source. The conversion is also extremely fast and produces a slightly smaller file (no MP4 atom overhead).
- When do I need raw AAC instead of M4A?
- HLS streaming (Apple's HTTP Live Streaming) uses ADTS-AAC segments. Shoutcast and Icecast Internet radio servers expect raw AAC streams. Embedded broadcast hardware (Axia, Telos) often only parses ADTS. Some legacy in-car head units also require .aac, not .m4a.
- Will my metadata (title, artist, cover art) be preserved?
- No — ADTS-framed AAC has no metadata layer. The MP4 atoms holding ID3-equivalent tags and artwork are discarded during extraction. If you need metadata, keep the M4A or add ID3v2 tags to the .aac afterward.
- Are my files uploaded?
- No. FFmpeg WebAssembly runs entirely in your browser. The container is unwrapped locally — your audio never leaves your device.
//related_converters
Related Converters
Similar conversions you might need.
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→Convert AAC to OGG
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→Convert AAC to FLAC
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→Convert M4A to WAV
Convert M4A (AAC) audio to uncompressed WAV for editing in DAWs, broadcast, and forensic workflows.
→Convert M4A to OGG
Convert M4A (AAC) to OGG Vorbis for open-source media libraries, game engines, and Linux ecosystems.
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