View source for Bwav

Bwav is an audio stream format used by the [[aal::atom]] library. It is primarily a lightweight header followed by audio sample data.

== File Structure ==
Bwav is little-endian. The file alignment is 4 bytes despite the sample data alignment. This page is based on version 1, which is the only currently known version.

# Header
# Channel Info Array
# Channel Sample Data Array

== Structures ==

=== Header ===
{| class="wikitable"
|+
!Offset
!Size
!Type
!Description
|-
|0x0
|0x4
|u32
|Magic - "BWAV"
|-
|0x4
|0x2
|u16
|Byte Order Mark
|-
|0x6
|0x2
|u16
|Version
|-
|0x8
|0x4
|u32
|Samples Hash - Hash of sample data region?
|-
|0xc
|0x2
|u16
|Flags - Bit 0 indicates this is a prefetch bwav
|-
|0xe
|0x2
|u16
|Channel Count
|}

=== Channel Info ===
Immediately follows header. One channel info per channel, variable length though almost always 0x4c (with 1 loop point). Channel info is tightly packed one after the other.
{| class="wikitable"
|+
!Offset
!Size
!Type
!Description
|-
|0x0
|0x2
|u16
|Encoding - 0 = Pcm16, 1 = DspAdpcm, 2 = Opus
|-
|0x2
|0x2
|u16
|Channel Pan - 0 = Left, 1 = Right, 2 = Center, 3 = LFE, 4 = LS, 5 = RS, 6 = Invalid?
|-
|0x4
|0x4
|u32
|Sample Rate
|-
|0x8
|0x4
|u32
|Non-Prefetch Sample Count
|-
|0xc
|0x4
|u32
|File Sample Count  (identical to previous field when non-prefetch bwav)
|-
|0x10
|0x20
|u16[16]
|Dsp-Adpcm Coefficients
|-
|0x30
|0x4
|u32
|Non-Prefetch Sample Data Offset
|-
|0x34
|0x4
|u32
|Sample Data Offset
|-
|0x38
|0x2
|u16
|Loop Point Count - Only observed as 1 despite support for multiple
|-
|0x3a
|0x2
|u16
|Base Loop Point - Default loop point
|-
|0x3c
|0x4
|u32
|Loop End - base sample of end after final loop point, 0xffff'ffff suggests no loop
|-
|0x40
|0xc * Loop Point Count
|Loop Point
|Loop Point Array - variable sized array of loop points
|}

==== Loop Point ====
A loop point provides a seek point to a specific sample offset. Often only 1 loop point exists, it's role being the start of a single looping region.
{| class="wikitable"
|+
!Offset
!Size
!Type
!Description
|-
|0x0
|0x4
|u32
|Loop Start - base sample of loop point start
|-
|0x4
|0x6
|Adpcm Context
|Adpcm Context - Snapshot of dsp-adpcm context at the sample offset of loop start
|-
|0xa
|0x2
|
|Zero-padding
|}

===== Adpcm Context =====
{| class="wikitable"
|+
!Offset
!Size
!Type
!Description
|-
|0x0
|0x2
|u16
|Predictor Scale
|-
|0x2
|0x4
|s16[2]
|History Array
|}

=== Sample Data ===
The start of each channel's sample data is aligned up by 64 bytes in file, despite the 4-byte file alignment, outside the last channel, which is truncated to the last non-zero sample (including zeroed samples in a dsp-adpcm block).
{| class="wikitable"
|+
!Format
!Type
!Description
|-
|Pcm16
|2 bytes per sample
|16-bit signed PCM sample data.
|-
|Dsp-Adpcm
|8-byte block array, up to 14 samples per block
|8-bit header for decoding, followed by up to 14 4-bit compressed samples.
|-
|Opus
|
|Header followed by opus data.
|}
[[Category:File formats]]