The bext chunkįollowing the ds64 chunk, we have the bext chunk from the BWF specification. So the final four bytes of a typical ds64 chunk are 0s, indicating no table entries. Finally, a ds64 chunk can have a table containing the sizes of any other huge chunks, but usually this would be unused since it is likely only the ‘data’ chunk that will grow larger than 4GB. This chunk is usually only present for non-PCM audio formats as it is trivial to calculate the sample count for PCM from the byte count. The sample count is optional really, as it corresponds to the sample count found in the ‘fact’ chunk of a standard WAV file. These are the RIFF size, which is the size of the entire file minus 8 bytes, the data size, which is the number of bytes of sample data in the ‘data’ chunk and the ‘sampleCount’ which is the number of samples.

The ds64 ChunkĪ ds64 chunk consists of three 8 byte integers and a four byte integer. If the overall file size does not grow beyond 4GB, then the junk chunk is simply left in place, and media players will just ignore it. If the overall size of the entire WAV file grows to over 4GB, then we will turn this “JUNK” chunk into a ‘ds64’ chunk. This is of size 28 bytes, and initially is all set to zeroes. But to support RF64, we add a “JUNK” chunk. Then we have the ‘WAVE’ identifier (another 4 bytes), and following that in a normal WAV file we would usually expect the format chunk (with the ‘fmt ‘ 4 byte identifier).

However, for large files, instead of ‘RIFF’, ‘RF64’ is used, and the following four byte integer for the RIFF size is then ignored (it should be set to -1). File Headerįirst of all, a WAV file starts with the byte sequence ‘RIFF’ and then has a four byte size value, which is the number of bytes following in the entire file. In this post, I’ll explain how you can make a class to create Broadcast Wave Files using NAudio that supports large file sizes using the RF64 extension, and includes the “bext” chunk from the BWF specification. The second is the Broadcast Wave Format (BWF) which builds on the existing WAV format and specifies various extra chunks containing metadata.

The first is the RF64 extension, which overcomes the inherent limitation that WAV files cannot be larger than 4GB. There are two extensions to the standard WAV file format which you may sometimes want to make use of.

What is a riff wav file