WAV 64 bit - RF64 - MBWF | Read Easy Explanation >

WAV 64 bit (RF64) is extended format of WAV file (PCM format).

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What is WAV RF64

RF64 is intendent to support:

1. file size more 2 Gbyte;
2. multichannel audio.

Native WAV format support 32-bit (2 Gbyte) file size only due size variable limitations (32 bit integer). First symbolic sequence into WAV 32 bit file (WAV identificator) is "RIFF".

First symbolic sequence into WAV64 file is "RF64".

How audio converter AuI ConverteR 48x44 works with RF64

WAV 64 vs WAV RF64

WAV 64 (WAV 64 bit) and WAV RF64 are different formats.

WAV may have bit depth 64 bit.  We can call it as WAV 64 bit.

Standard WAV-header fields, that are responsible for size, have 32-bit length. These fields may be replaced to 64 bit ones. That file type may be called as WAV 64 or WAV 64 bit.

WAV RF64 is satndart WAV format extension, that contains special header and special rules to fill standard WAV headers.

WAV structure

WAV 32 bit chunks

Chunks are information blocks, that contains chunk identifier, the block size and information.

1. RIFF-header (format identificator);
2. fmt-chunk (sample rate, channels count, sample size and etc.);
3. other chunks are possible;
4. data-chunk (audio stream length, audio stream);
5. other chunks are possible.

WAV (RF64) file chunks

1. RF64-header (format identificator, analog RIFF-chunk of WAV 32 bit);
2. dsd64-chunk (audio stream length)
3. fmt-chunk (sample rate, channels count, sample size and etc.);
4. possible other chunks;
5. data-chunk (audio stream);
6. possible other chunks.

How RF64 works

According WAV RF64 specification WAV files are processed next way:

1) Create WAV 32 bit file which contains:

       RIFF-header;

      JUNK-chunk (empty or dummy chunk); 

       fmt-chunk;

       possible other chunks;

2)  Append to end of file data-chunk. Append audio stream data.

3) End recording.

4) If recorded WAV-file less 4 Gbyte:

           - set up size data into RIFF, data chunks;

           - close file.

5) If recorded WAV-file more 4 Gbyte:

- replace RIFF-header to RF64-header;

- replace JUNK-chunk to dsd64-chunk with filling information about size recorded file;

- set up 0xFFFFFFFF data-chunk size;

- close file.

MBWF is RF64 file with bext-chunk. The terms "RF64" and "MBWF" can used as synonymous.

Compatible audio converters

AuI ConverteR 48x44

AuI ConverteR is capable to read RF64 or RIFF (32-bit) and convert with automatical selecting format of audio file by its size.

Compatible audio players

foobar2000

WinAmp

Download samples

mono

stereo

multichannel 5.1

multichannel 7.1

Example

When convert sample rate of wav-file changing of output file size (relative to input file).

For upsampling: input file (wav 32 bit or RIFF) have sampling rate 44 kHz and size 2 Gbyte. Make conversion to 176 kHz. Output file have size 2 * (176/44) =8 Gbyte. Output file must have format wave 64 bit or RF64.

References

1. EBU Tech 3306 - MBWF / RF64: An Extended File Format for Audio

2. EBU Recommendation R111-2007 - Multichannel use of the BWF audio file format (MBWF)