How to Convert MP4 to AIFF

AIFF is an uncompressed audio format that works well in many Mac apps, audio editors and digital audio workstations. An MP4 file (often labelled MPEG-4) is a container that can hold video, one or more audio tracks, subtitles and metadata. Converting MP4 to AIFF means taking one audio track out of that container and decoding it to uncompressed PCM audio. The video is discarded.

Before you start

• Confirm the file has an audio track. A screen recording or camera clip saved without sound has nothing to convert.
• Know what is inside. Most MP4 and M4A files carry AAC audio. Some carry ALAC (lossless) or another codec. A media inspector or ffprobe shows the codec, sample rate and channel count.
• Expect larger files. Uncompressed AIFF takes much more space than compressed AAC, so check free disk space before converting long recordings or many files.
• Understand the quality limit. Converting lossy AAC to AIFF does not restore detail that compression removed. It only gives you an uncompressed copy that is easier to edit.
• Check for copy protection. Purchased or rented media with DRM generally cannot be converted with standard tools.
• Keep the original. Conversion writes a new file, but keep the source MP4 until you have checked the AIFF.

Decide where the conversion runs. FFmpeg and desktop audio editors process the file on your own computer. Browser-based converters may upload your file to a remote server. Treat any privacy, retention or deletion claim from an online service as something to verify in its current terms. Do not upload recordings that contain private conversations, meetings or client material unless you have confirmed how the service handles them.

Step-by-step instructions

Option 1: FFmpeg on Windows, macOS or Linux

FFmpeg is a free command-line tool that runs locally. It gives you exact control over the output format.

• Install FFmpeg using your platform's usual method, such as a package manager or an official build, and make sure the ffmpeg command works in a terminal.
• Open a terminal in the folder that contains your file.
• Inspect the file: ffprobe input.mp4. Note the audio stream's codec, sample rate and channels.
• Convert the first audio track to 16-bit AIFF: ffmpeg -i input.mp4 -vn -c:a pcm_s16be output.aiff
• For 24-bit output, which is useful for editing headroom or a 24-bit source, use pcm_s24be instead of pcm_s16be.
• If the file has several audio tracks, choose one explicitly. For example, -map 0:a:1 selects the second audio track: ffmpeg -i input.mp4 -map 0:a:1 -c:a pcm_s16be output.aiff

What the options do: -vn drops the video, and -c:a pcm_s16be writes big-endian 16-bit PCM, the standard sample format for AIFF. Without extra options, FFmpeg keeps the source sample rate and channel layout. If a project needs a specific rate, add -ar 48000 or -ar 44100. Change it only when the destination requires it.

To convert a folder of files in a macOS or Linux shell, run: for f in .mp4; do ffmpeg -i "$f" -vn -c:a pcm_s16be "${f%.mp4}.aiff"; done. In the Windows Command Prompt, run: for %f in (.mp4) do ffmpeg -i "%f" -vn -c:a pcm_s16be "%~nf.aiff". Inside a batch file, write %%f instead of %f.

Option 2: A desktop audio editor

Audio editors such as Audacity can import the audio from an MP4 and export it as AIFF. Some versions need the separate FFmpeg import library before they can open MP4 files. Menu names differ between versions, so follow the help for the version you have installed. The general sequence is the same everywhere.

• Import or open the MP4 file in the editor.
• If the file has several audio tracks, confirm which one was imported.
• Trim or edit if needed. The original MP4 is not modified.
• Use the export function, choose AIFF as the format, and pick the bit depth. 16-bit works for general use, and 24-bit or 32-bit float suits further editing.
• Leave the sample rate at the project or source rate unless the destination requires something else.
• Save the file with an .aiff or .aif extension.

Check the output

• Play the AIFF from start to finish, or spot-check the beginning, middle and end, to confirm the sound is present and in sync with what you expected.
• Compare durations. The AIFF should match the length of the source audio track.
• Run ffprobe output.aiff and confirm the codec is PCM (for example pcm_s16be), and that the sample rate and channel count match your settings.
• Open the file in the app where you plan to use it, such as a DAW, video editor or music library, to confirm it imports correctly.
• Check the file size. AIFF should be much larger than the AAC audio inside the MP4. A very small file may mean the wrong track was used or the audio is silent.

Know the format limits. AIFF stores sizes as 32-bit values, so a single file cannot exceed about 4 GB. Very long multichannel or high-sample-rate recordings may need to be split. Metadata such as titles, artwork and chapters may not carry over from MP4 to AIFF, and support for AIFF tags varies between apps.

Common problems and next steps

• FFmpeg reports that the output does not contain any stream: the MP4 has no audio track, or your -map option points to a track that does not exist. Check the stream list with ffprobe.
• The AIFF is silent or contains the wrong language or commentary: the file has several audio tracks. Select the correct one with -map 0:a:N, where N counts from 0.
• The editor cannot open the MP4: install the import library the editor requires, or extract the audio with FFmpeg first and open the resulting AIFF.
• The file is protected or fails to decode: DRM-protected media cannot be converted with standard tools. Use an unprotected source that you have the right to use.
• The output sounds no better than the original: this is expected. AIFF preserves the decoded audio exactly but cannot improve lossy AAC. For the best result, start from the highest-quality source available.
• The destination expects a specific format: some workflows require a particular sample rate or bit depth. Set -ar and the PCM codec to match, and avoid unnecessary resampling.
• You need a smaller file instead: if the only goal is to keep the audio from an MP4, extracting it to M4A without re-encoding (ffmpeg -i input.mp4 -vn -c:a copy output.m4a) keeps the original quality at a fraction of the size.

The same steps apply whether a file is labelled MP4, MPEG-4 or M4A. What matters is the audio stream inside it, so inspect the stream first, choose the track and bit depth deliberately, and check the AIFF before deleting the source.