BWF
Encyclopedia
Broadcast Wave Format is an extension of the popular Microsoft WAVE
audio format and is the recording format of most file-based non-linear digital recorders used for motion picture, radio and television
production.
It was first specified by the European Broadcasting Union
in 1997, and updated in 2001 and 2003.
The purpose of this file format is the addition of metadata
to facilitate the seamless exchange of sound data between different computer platforms and applications. It specifies the format of metadata
, allowing audio processing elements to identify themselves, document their activities, and permit synchronization with other recordings. This metadata is stored as extension chunks in a standard digital audio WAV file.
Files conforming to the Broadcast Wave specification have names ending with the extension .WAV.
In addition to the common WAVE chunks, the following extension chunks can appear in a Broadcast Wave file:
For more information, see EBU BWF User Guide
Unfortunately, this compatibility also preserves the filesize limitation that WAV files have (4 GiB
in theory, 2 GiB in practice because most implementations use signed integer
).
In order to be able to store audio which would exceed this limit, 2 different chunks exist allowing the audio material to be spread across several files: cont & link (see list above)
Since there is no official naming convention for these subsequent files, and it is still desirable to see at a glance which ones belong to a continuous piece of audio, a lot of programs apply a numbering scheme to the file suffix: .wav, .w01, .w02, ..., .wNN.
Each of those segments is a regular Wave/BWF file, but players that are aware of the continue/link chunk will treat all segments as one single, long piece of audio when opening the first segment ".wav".
As an extension, RF64
is a BWF-compatible multichannel file format enabling file sizes to exceed 4 GiB that has been specified in 2006.
The axml chunk allows users to incorporate data compliant with the XML format with the audio; the chunk may contain data fragments from one or more schema.
BWF is specified for use in MXF by SMPTE standard 382.
WAV
Waveform Audio File Format , is a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs...
audio format and is the recording format of most file-based non-linear digital recorders used for motion picture, radio and television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
production.
It was first specified by the European Broadcasting Union
European Broadcasting Union
The European Broadcasting Union is a confederation of 74 broadcasting organisations from 56 countries, and 49 associate broadcasters from a further 25...
in 1997, and updated in 2001 and 2003.
The purpose of this file format is the addition of metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
to facilitate the seamless exchange of sound data between different computer platforms and applications. It specifies the format of metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
, allowing audio processing elements to identify themselves, document their activities, and permit synchronization with other recordings. This metadata is stored as extension chunks in a standard digital audio WAV file.
Files conforming to the Broadcast Wave specification have names ending with the extension .WAV.
In addition to the common WAVE chunks, the following extension chunks can appear in a Broadcast Wave file:
- Original Bext chunk (Broadcast Extension - 'bext')
- iXMLIXMLiXML is an open standard for the inclusion of location sound metadata in Broadcast Wave audio files. This includes things like Scene, Take and Notes information....
chunk ('iXML') - Quality chunk ('qlty')
- MPEG audio extension chunk ('mext')
- Peak Envelope chunk ('levl')
- link chunk ('link')
- axml chunk ('axml')
For more information, see EBU BWF User Guide
WAV compatibility
Since the only difference between a BWF and a "normal" WAV is the extended information in the file header (Bext-Chunk, Coding-History, etc...), a BWF does not require a special player for playback.Unfortunately, this compatibility also preserves the filesize limitation that WAV files have (4 GiB
Gibibyte
The gibibyte is a standards-based binary multiple of the byte, a unit of digital information storage. The gibibyte unit symbol is GiB....
in theory, 2 GiB in practice because most implementations use signed integer
Integer (computer science)
In computer science, an integer is a datum of integral data type, a data type which represents some finite subset of the mathematical integers. Integral data types may be of different sizes and may or may not be allowed to contain negative values....
).
In order to be able to store audio which would exceed this limit, 2 different chunks exist allowing the audio material to be spread across several files: cont & link (see list above)
Since there is no official naming convention for these subsequent files, and it is still desirable to see at a glance which ones belong to a continuous piece of audio, a lot of programs apply a numbering scheme to the file suffix: .wav, .w01, .w02, ..., .wNN.
Each of those segments is a regular Wave/BWF file, but players that are aware of the continue/link chunk will treat all segments as one single, long piece of audio when opening the first segment ".wav".
As an extension, RF64
RF64
RF64 is a BWF-compatible multichannel file format enabling file sizes to exceed 4 GB. It has been specified by the European Broadcasting Union.The file format is designed to meet the requirements for multichannel sound in broadcasting and audio...
is a BWF-compatible multichannel file format enabling file sizes to exceed 4 GiB that has been specified in 2006.
The axml chunk allows users to incorporate data compliant with the XML format with the audio; the chunk may contain data fragments from one or more schema.
BWF is specified for use in MXF by SMPTE standard 382.
See also
- RF64RF64RF64 is a BWF-compatible multichannel file format enabling file sizes to exceed 4 GB. It has been specified by the European Broadcasting Union.The file format is designed to meet the requirements for multichannel sound in broadcasting and audio...
, A BWF-compatible multichannel file format enabling file sizes to exceed 4 GiB - WAVWAVWaveform Audio File Format , is a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs...
- MXFMXFMaterial eXchange Format is a container format for professional digital video and audio media defined by a set of SMPTE standards.- A brief summary of MXF :...
, Material eXchange Format - Advanced Authoring FormatAdvanced Authoring FormatThe Advanced Authoring Format is a professional file interchange format designed for the video post production and authoring environment. The AAF was created by the Advanced Media Workflow Association . The AMWA develops specifications and technologies to facilitate the deployment and operation...
External links
- EBU Tech 3285 - Specification of the Broadcast Wave Format (BWF) - Version 1 - second edition (2001)
- EBU Tech 3285-s1 - Specification of the Broadcast Wave Format (BWF) - Supplement 1, MPEG Audio - first edition (1997)
- EBU Tech 3285-s2 - Specification of the Broadcast Wave Format (BWF) - Supplement 2, Capturing Report - first edition (2001)
- EBU Tech 3285-s3 - Specification of the Broadcast Wave Format (BWF) - Supplement 3, Peak Envelope Chunk - first edition (2001)
- EBU Tech 3285-s4 - Specification of the Broadcast Wave Format (BWF) - Supplement 4, Link Chunk - first edition (2003)
- EBU Tech 3285-s5 - Specification of the Broadcast Wave Format (BWF) - Supplement 5,
Chunk - first edition (2003)