RF64

RF64 is an extension of the WAV audio file format designed to overcome the 4 gigabyte size limit of the original RIFF-based WAV. It achieves this by using 64-bit size fields inside a dedicated ds64 chunk, while preserving the standard RIFF/WAVE structure. In an RF64 file, the RIFF chunk size is set to 0xFFFFFFFF, indicating that the true sizes are stored in the ds64 chunk near the beginning of the file. This design allows accurate representation of very large audio files while remaining compatible with many readers that know how to handle the extended chunk.

The ds64 chunk stores 64-bit values for the overall file length and the data chunk length, as well as a 64-bit sample count. It may also include a 64-bit field describing the length of an extended chunk offset table used for indexing. The actual audio data remains in a standard data chunk, and other RIFF/WAVE chunks such as fmt and fact can appear as usual. RF64 files therefore support large, high-resolution, or multi-channel audio data that exceed 32-bit limits.

RF64 is widely supported by modern digital audio workstations, editors, and broadcasting workflows, and is commonly used in film, video production, music mastering, and archival work. Some older playback software or consumer tools may not recognize RF64, potentially misinterpreting the file. When interoperability is critical, practitioners may provide a standard WAV copy for legacy tools or convert to RF64 only when necessary.

RF64 is part of the RIFF-based family and relates to formats such as Broadcast Wave Format (BWF). It preserves WAV metadata structures while enabling large-file handling, making it a practical option for professional audio workflows.