AAC vs PCM: Compare Audio Quality and File Size

Many recording apps, cameras, screen recorders and audio interfaces offer two audio choices: PCM and AAC. One keeps every sample your input device captured. The other shrinks the file by discarding detail it predicts you will not hear. This guide explains how the two formats differ and how to pick one for your recording.

What you are comparing

PCM (pulse-code modulation) is uncompressed digital audio. The signal is stored as a series of amplitude values taken at a fixed sample rate, such as 44.1 kHz or 48 kHz, and a fixed bit depth, such as 16 or 24 bits. PCM is usually saved in WAV or AIFF files and can also be carried inside some video containers, such as MOV.

AAC (Advanced Audio Coding) is a lossy compressed format. Its encoder analyses the sound and removes information it judges less audible, then stores the rest at a chosen bitrate. AAC is common in M4A audio files and in MP4 video, and it has several profiles: AAC-LC is the general-purpose one, while HE-AAC targets lower bitrates.

The comparison here covers these two formats as options for saving or exporting recordings: voice, music, webcam clips and screen captures. It does not rank specific apps or devices, whose encoders and settings vary.

Meaningful differences

File size and bitrate

PCM size follows a fixed formula: sample rate × bit depth × number of channels. For example, 48 kHz, 16-bit stereo works out to 1,536 kbps, about 11.5 MB per minute before container overhead. At 24 bits the same recording takes about 17.3 MB per minute. An AAC file's size depends on the bitrate you or the app selects rather than on that formula. At 256 kbps a minute of audio is roughly 1.9 MB, and at 128 kbps roughly 1 MB. These figures are arithmetic from the bitrates, not measurements of a particular app.

Audio quality

PCM reproduces exactly what was captured at its sample rate and bit depth. It does not fix the source: background noise, room echo and clipping from an input level set too high are preserved just as faithfully as the voice. AAC quality depends on bitrate, profile and the encoder used. At higher bitrates many listeners find AAC hard to tell apart from the original. At low bitrates artifacts become more likely, such as smeared transients, a swirly or watery high end and noise that sounds unnatural. Whether a given setting is audible on your material can only be decided by listening, ideally on the output device your audience will use.

Editing and re-encoding

PCM is the safer working format. The format itself adds no loss when you cut, mix or process, although your edits still change the sound. With AAC, each decode and re-encode cycle can add further loss, so repeated exports from AAC to AAC gradually degrade the audio. AAC streams also include encoder delay (priming samples) that different tools handle differently. If you cut, loop or align clips precisely, check sync after importing AAC material.

Compatibility

WAV files with PCM open in nearly every audio editor and video editing program. AAC in MP4 or M4A is the more common choice for playback on phones, in browsers and on sharing platforms, and MP4 video normally carries AAC audio. Some players and upload services may not accept PCM inside an MP4 file. Check the requirements of the destination you use. Note that AAC is also the name of a Bluetooth codec. A PCM file played through Bluetooth headphones may still be compressed on the way to the output device, so the file format and the wireless link are separate questions.

Privacy and file handling

Neither format is inherently more private. Larger PCM files take longer to upload and use more storage or cloud quota. Either container can carry metadata such as creation time or device name, depending on the app that wrote it. Before sharing, check what metadata your files contain. Confirm in the app's own documentation whether it processes audio on your device or uploads it.

Practical trade-offs

• Voice-over, podcast or narration you plan to edit: PCM keeps full detail through editing. Export a compressed copy only at the end.
• Music, instruments or field recording: PCM at 24-bit gives more headroom if your input level is set conservatively. Recording equipment often defaults to it.
• Webcam clips and screen recordings for quick sharing: AAC in MP4 keeps files small and widely playable, which usually matters more than editing headroom.
• Long recordings on limited storage, such as lectures or meetings: AAC lets far more hours fit on a card or phone. Choose a bitrate that keeps speech clear.
• Video calls: the call app compresses audio with its own codec before sending it. Your local file format setting does not change what other participants hear. It matters only if you also record the call locally.

Separate what specifications tell you from what needs testing. Bitrate, sample rate, bit depth and file size can be calculated or read from settings. Whether AAC at a given bitrate is acceptable for your voice, microphone and room cannot. To find out, record the same short passage both ways with the same input device and input level. Then compare them on the speakers or headphones your listeners are likely to use.

Choose for the use case

• Choose PCM if you will edit, mix or process the recording, or if it is a master you want to keep long term.
• Choose AAC if the file is a final deliverable for playback or sharing, or if storage and upload time are tight.
• Record in PCM and export to AAC if you need both editing quality and small shareable files.
• Match the sample rate to your project: 48 kHz is the usual convention for video, while 44.1 kHz is common for music-only projects.
• If an upload service or player lists accepted formats, follow that list rather than a general rule.

Whichever format you pick, the quality of the original capture matters more than the container. Set a sensible input level, reduce background noise at the source and select the correct microphone before you press record.