Convert M4A to AAC

Yes, and it is worth planning around. Both formats are lossy, so the AAC encoder is working from audio that has already been through one psychoacoustic pass, and its own decisions compound the first set. At 192 kbps or above the result is still transparent for most listening. If you have a lossless master anywhere, encoding the AAC from that instead avoids the double pass entirely. An M4A holds AAC in most cases, or Apple Lossless (ALAC) when it came from a lossless rip. AAC is lossy but more efficient than MP3, and it handles up to 48 channels natively rather than being bolted onto a stereo design.

DRM. A subset of M4A files are encrypted by the store or the software that issued them, and encrypted audio cannot be decoded by any converter. Anything you ripped yourself, recorded, or bought without protection converts normally; a licensed purchase will not. M4A hides two very different things behind one extension — lossy AAC and lossless ALAC — and non-Apple hardware support is inconsistent.

Default is 192 kbps for lossy AAC; pass-through for lossless AAC. Override to 320 kbps for audiophile or 64-96 kbps for spoken-word audiobooks (transparent for voice, halves the file size).

If M4A is lossy and AAC is lossless (e.g. MP3 → WAV), the AAC file is no better than the M4A — you can't recover information that's already been thrown away. If M4A is lossless and AAC is lossy, expect the AAC codec to recompress; at 192 kbps this is transparent for most content.

Yes — title, artist, album, year, track number, album art, and chapter markers (important for audiobooks) are read from M4A and written into the AAC container where the AAC format supports tags. M4B audiobook structure round-trips into M4B and AAX → M4B output.

Yes — drop a folder of M4A files in and we process them in parallel. Premium has more parallel workers and no per-file size cap, so a 500-file batch finishes in minutes rather than tens of minutes.

By default yes (48 kHz M4A → 48 kHz AAC). If you need to downsample for compatibility (e.g. 96 kHz → 44.1 kHz for CD burning) the advanced sample-rate option does this with high-quality resampling.

Yes — the loudness-normalize option applies ITU-R BS.1770 / EBU R128 normalization to the AAC output, targeting -14 LUFS (streaming standard), -16 LUFS (podcast standard), or -23 LUFS (audiobook standard). Useful when batch-converting tracks with varying mastering levels.

MP3 plays universally. AAC plays on Apple, most Android, Sonos. FLAC plays on Sonos and Android, less well on older iPods. M4B audiobooks play with chapter navigation on iOS Books, Audiobookshelf, and Smart Audiobook Player. The advanced options include device presets.

Yes — uploaded M4A files are processed in isolated workers and deleted within minutes. We never play, store, or share the audio content. Especially important when working with personal audiobook libraries.

Same-codec re-mux: 10-30 seconds. Re-encode to a different codec: typically 10-20% of source duration, so a 10-hour audiobook finishes in 60-120 minutes. Chapter markers survive the round-trip and split cleanly.