Convert M4A to AIFF — Free Online Tool
Convert M4A files (AAC-encoded audio from iTunes or podcasts) to AIFF, Apple's uncompressed lossless format, using PCM 16-bit big-endian encoding. This is ideal when you need to take lossy AAC audio and bring it into a lossless container for use in professional macOS audio workflows or DAWs.
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FFmpeg Command
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Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
M4A files typically contain AAC-encoded audio, which is a lossy compressed format. During this conversion, FFmpeg decodes the AAC audio stream from the MPEG-4 container back to raw PCM audio samples, then re-encodes those samples as 16-bit signed big-endian PCM (pcm_s16be) and wraps them in an AIFF container. Because AAC is lossy, this is a lossy-to-lossless conversion — the AIFF output will be uncompressed and bit-for-bit stable from this point forward, but it cannot recover audio detail that AAC's compression originally discarded. The resulting AIFF file will be significantly larger than the source M4A, reflecting the uncompressed nature of PCM audio. Chapter and iTunes metadata from the M4A are not carried over, as AIFF does not support those features.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary, the open-source multimedia processing engine that handles all decoding, encoding, and container operations for this M4A-to-AIFF conversion. |
-i input.m4a
|
Specifies the input file — an M4A container, which typically holds AAC-compressed audio. FFmpeg will demux this MPEG-4 container and pass the AAC audio stream to its decoder. |
-c:a pcm_s16be
|
Sets the audio codec to 16-bit signed big-endian PCM, which is the standard uncompressed audio encoding used by AIFF files. This decodes the AAC from the M4A and re-encodes it as raw PCM samples suitable for the AIFF container. |
output.aiff
|
Specifies the output file. The .aiff extension tells FFmpeg to wrap the PCM audio in an Audio Interchange File Format container, the uncompressed audio format native to macOS and professional Apple audio applications. |
Common Use Cases
- Importing purchased iTunes music (M4A/AAC) into a macOS DAW like Logic Pro or GarageBand, which works natively with AIFF for editing and arrangement
- Preparing podcast episode masters downloaded as M4A for delivery to a radio station or broadcast facility that requires uncompressed AIFF files
- Bringing an M4A audiobook or spoken-word recording into a professional audio editor for cleanup, noise reduction, or remastering without further generational loss
- Archiving a collection of M4A recordings into AIFF for long-term storage in a format that won't degrade with repeated decoding or re-encoding
- Converting M4A field recordings or voice memos from an iPhone into AIFF for import into Final Cut Pro or other Apple professional video tools that prefer AIFF audio
- Supplying uncompressed audio to a mastering engineer or post-production studio whose workflow requires AIFF rather than compressed formats
Frequently Asked Questions
No — M4A files use AAC, which is a lossy codec, meaning some audio detail is permanently removed during the original encoding. Converting to AIFF decodes that AAC audio to uncompressed PCM, but it cannot restore the data that AAC discarded. The AIFF file will be an exact, stable representation of what the AAC decoded to, and it will not degrade further with subsequent processing — but it won't sound better than the source M4A.
AAC compression in M4A files achieves very high compression ratios — a 128k AAC file uses roughly 1MB per minute of audio. AIFF stores audio as raw, uncompressed PCM samples: at 16-bit stereo and 44.1kHz, that's approximately 10MB per minute. A 50MB M4A file could easily expand to 300–500MB as an AIFF, which is expected and normal. This size reflects the true uncompressed audio data, not any quality improvement.
Partial metadata preservation is possible, but AIFF's metadata support is more limited than M4A's. Basic ID3-style tags such as artist, album, and title may be copied over by FFmpeg, but iTunes-specific metadata, chapter markers, and gapless playback information stored in the M4A will not transfer to the AIFF output. If metadata preservation is critical, you should verify the tags in your destination application after conversion.
pcm_s16be stands for signed 16-bit big-endian PCM, which is the standard AIFF audio format used by most macOS applications and CD-quality audio workflows. If your original M4A was encoded at a high bitrate (256k or 320k AAC) and you need it for professional audio production at 24-bit depth, you can change the codec in the FFmpeg command to pcm_s24be for 24-bit output, which provides a wider dynamic range. For most consumer M4A sources, 16-bit is sufficient.
Replace pcm_s16be in the command with another supported AIFF codec. For 24-bit output, use: ffmpeg -i input.m4a -c:a pcm_s24be output.aiff. For 32-bit integer, use pcm_s32be, or for 32-bit float, use pcm_f32be. These higher bit depths are useful in professional audio production contexts but will produce proportionally larger files. Note that since the source is lossy AAC, the extra bit depth won't recover lost audio detail — it only increases headroom for further processing.
Yes, with a small modification. In a Unix/macOS terminal you can run: for f in *.m4a; do ffmpeg -i "$f" -c:a pcm_s16be "${f%.m4a}.aiff"; done. On Windows Command Prompt, use: for %f in (*.m4a) do ffmpeg -i "%f" -c:a pcm_s16be "%~nf.aiff". This processes every M4A in the current folder and outputs a matching AIFF file. The browser-based tool on this page processes one file at a time, so the FFmpeg command is the recommended approach for bulk conversions.
Technical Notes
The conversion from M4A to AIFF involves a full decode-and-re-encode cycle rather than a simple remux, because AAC (the codec inside M4A) and PCM (the codec inside AIFF) are fundamentally incompatible audio representations. FFmpeg first demuxes the MPEG-4 container, decodes the AAC bitstream using its internal AAC decoder, and then re-encodes the raw PCM samples to 16-bit big-endian format in an AIFF container. The big-endian byte order (BE) is a historical artifact of AIFF's origins on Motorola 68k processors in early Macs — modern macOS handles this transparently, but some non-Apple tools may prefer WAV with little-endian PCM instead. If your M4A source contains multiple audio tracks (uncommon but possible with certain podcast or audiobook files), only the first audio track will be converted. AIFF does not support chapters, so any chapter metadata in an M4A audiobook will be silently dropped. The output sample rate will match the source M4A's sample rate — most iTunes-encoded M4A files are 44100Hz, which maps cleanly to standard AIFF. Files encoded at 48000Hz (common for video-sourced audio) will also convert cleanly without resampling.