When you record, edit or archive an audio project, the working format is almost always uncompressed. Yet acronyms like PCM, WAV, BWF and AIFF are often used as synonyms. They are not: some describe how the samples are encoded, others the container that holds them. Getting this straight helps you exchange files without surprises.
PCM: the encoding, not the file
PCM (Pulse Code Modulation) is the most direct way to represent digital audio: a sequence of samples, each with a numeric value, one after another, with no compression at all. It is not a file format but a type of content.
A PCM stream is described by three parameters:
- sample rate (for example 48,000 samples per second);
- bit depth (16, 24 or 32 bits, integer or floating point);
- number of channels (mono, stereo or multichannel).
Without this information a raw PCM stream is just a long sequence of numbers that cannot be interpreted. That is why you need a container that declares them.
WAV: the most widespread container
WAV is a container based on the RIFF structure, organized into blocks called chunks. Each chunk has a four-character identifier and a length. The two essential ones are:
- the fmt chunk, which describes sample rate, bit depth, channels and encoding type;
- the data chunk, which holds the actual samples.
In the vast majority of cases a WAV contains PCM, but the format also allows other encodings. Optional chunks can hold markers, loop points or text information.
The 4 GB limit
The RIFF format uses 32-bit length fields, so a WAV file cannot exceed about 4 GB. At 48 kHz, 24-bit stereo that is more than three and a half hours, but with multichannel recordings the limit is reached quickly. Many recorders automatically split the recording into consecutive files once the threshold is reached.
Broadcast Wave and RF64
BWF (Broadcast Wave Format) is a WAV with an extra chunk called bext. It contains a description, originator, creation date and time and, above all, a time reference indicating the file's position relative to the start of the recording day. It is essential when working with video: when you import the files into a timeline, each one lands automatically in the right place.
RF64 is an extension designed to overcome the 4 GB limit, with 64-bit length fields. Many programs read it without trouble, but it is worth checking before delivering a file to someone else.
AIFF: the historical alternative
AIFF does the same job as WAV and originated in the Apple world. It uses a similar block structure, but stores numbers in a different byte order (big-endian, while WAV uses little-endian). For the listener nothing changes: quality is identical because the content is the same PCM.
Today virtually every DAW reads both formats. WAV has become the de facto standard for exchange, even among Mac users.
Comparison
| Format | Typical content | Metadata | Practical limit |
|---|---|---|---|
| WAV | PCM | Basic, optional chunks | 4 GB |
| BWF | PCM | Description, timecode | 4 GB |
| RF64 | PCM | Same as BWF | Well beyond 4 GB |
| AIFF | PCM | Basic | Similar to WAV |
Metadata: the weak spot
For a home archive, the most concrete problem with uncompressed formats is metadata. Title, artist, artwork and notes are handled inconsistently: some programs write tags inside the WAV, others ignore them, and others still delete them during processing. If an archive of recordings needs to stay organized, it is wise to also put the information into the file names and a simple catalog spreadsheet.
An example of a robust convention:
2026-03-14_interview-rossi_take02_48k24.wav
Date in year-month-day format, a short description, take number and technical parameters: the file remains understandable even if its internal metadata gets lost.
Which one to choose
- Recording and editing: 24-bit WAV, or 32-bit float if the recorder supports it.
- Working with video: BWF, for the time reference.
- Long multichannel recordings: RF64, after checking compatibility.
- Long-term archiving: WAV or a lossless format such as FLAC, which saves space without losing anything.
In my work I follow a rule that the original file of a recording is never overwritten: you work on copies and the original stays read-only.
In short
- PCM is the sample encoding; WAV and AIFF are containers that hold it.
- WAV has a limit of about 4 GB, overcome by the RF64 extension.
- BWF adds a description and a time reference, useful with video.
- AIFF and WAV have identical quality: only the file structure differs.
- Metadata in WAV files is fragile: a good file-naming convention is the best protection.
