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Broadcast Wave Format (BWF) is an extension of Microsoft WAV audio files. Read about BWF destination, content, and others.
March 5, 2023 updated | since August 27, 2012
Author: Yuri Korzunov,
Audiophile Inventory's developer with 25+ year experience in digital signal processing,
author of the articles that make audio easy for beginners
WAV file contains information blocks (chunks): audio data parameters, audio track metadata, etc. BWF is a special additional WAV-chunk that allows:
add more information for music production applications;
information to unite several audio files in single stuff (see 'time reference' below);
information about the loudness level of the audio file content. It's used for level normalization in broadcast applications.
Also, there is Multi-channel Broadcast Wave Format (MBWF) that is intended to storing of multichannel files with size above 4 GByte inside RF64 format.
first sample count since midnight (time reference);
version of the BWF;
reserved data;
history coding.
This BWF chunk contains description of coding process that is applied to the audio data. Each new coding application shall add a new string with the appropriate information. AuI ConverteR 48x44 according EBU R98 add "A=PCM,F=44100,W=16,M=mono,T=AuI ConverteR 48x44," string, where:
A - Coding Algorithm;
F - Sampling frequency, Hz;
W - Word Length, bits;
M - mode;
T - free text.
Version 1
UMID for an audio file is added to the reserved data area.
UMID (Unique Material Identifier) is a special code that is used to identify audiovisual materials (locally generated and globally unique identifier, standardized by the Society of Motion Picture and Television Engineers (SMPTE)).
Version 2
Loudness measurements for audio file is added to the reserved data area.
For regularize of values of loudness for different broadcast programs (as example, ads and movies), it needs to normalize the loudness of audio files. Audio files must contain their measured level of loudness too. Used algorithm is intended for objective estimation of subjective loudness. It's applicable for various program genres.
Integrated Loudness Value of the file in LUFS (measured by AuI ConverteR 48x44 according to ITU-R BS.1770-2) for multichannel files also;
Loudness Range of the file in LU (measured by AuI ConverteR 48x44 according to EBU – TECH 3342);
Maximum True Peak Level of the file expressed as dBTP (while it's not measured by AuI ConverteR 48x44);
Analog Digital Converter can bypass some peaks of level input signal. Then make oversampling possible restore this peaks: appear increasing of signal level (max 0.688 dB - see Rec. ITU-R BS.1770-2, p. 21).
Highest value of the Momentary Loudness Level of the file in LUFS (measured by AuI ConverteR 48x44);
Highest value of the Short-Term Loudness Level of the file in LUFS (measured by AuI ConverteR 48x44).
