BLAS LFD Resource Type
Author: Jagged Fel (jaggedfel621@gmail.com)
Site: http://idmr.empirereborn.net
Updated: 2009.10.05
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The BLAS Resource type is actually a *.VOC file (Creative Voice) within the
LFD and maintains the *.VOC file structure.  Because of the pre-existing file
format, the structure layout will be displayed a little different.

NOTE: The BLAS and VOIC resources are identical, the reason behind two
different types for the same WAV format are unknown. BLAS is typically weapons
and sound effect, VOIC is usually voice data. Substitute "VOIC" for "BLAS" in
this file to magically create "Resource_VOIC.txt".

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BLAS Structure

The following values are used through this and all of my file definitions
unless otherwise specified:
NAME	LENGTH	DESC
----	------	----
BYTE	1	unsigned 8-bit
CHAR	1	ASCII character
SHORT	2	signed Int16
INT	4	signed Int32

--
0x0	Header
0x10	VocHeader
0x2A	VocDataBlock[]
--

struct Header (size 0x10)
{
	0x0	CHAR[4]	"BLAS"
	0x4	CHAR[8]	Name
	0xC	INT	Length
}

struct VocHeader (size 0x1A)
{
	0x00	CHAR[19] "Creative Voice File"
	0x13	BYTE	Reserved (0x1A)
	0x14	SHORT	HeaderLength (0x1A)
	0x16	SHORT	Version (0x010A)
	0x18	SHORT	VersionVerify (0x1129)
}

struct VocDataBlock
{
	0x0	BYTE	Type
	#if (Type != 0)
	0x1	3BYTE	Length
	#if (Type == 1) (Sound Data)
	0x4	BYTE	FrequencyDivisor
	0x5	BYTE	Codec
	0x6	BYTE[Length-2]	AudioData
	#elseif (Type == 6) (Repeat)
	0x4	SHORT	NumRepeat
	#endif
	#endif
}

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BLAS Detail

For the most part, the Header is a formality, the only way to sync it into the
LFD file. Since this is simply a pre-existing file format that has
been placed into the LFD, the format is very reliable and is safe to use.

The VocHeader is for the most part fixed. There is technically a possiblity
of the Version and Verify values being different, but TIE sticks with the older
version, so we don't have to worry about it.

-- VocDataBlock --

The VocDataBlock array primarily consists of a single Sound Data block followed
by the EOF block (00). There are a handful of resources that use the Repeat
block, they all have a NumRepeat value of -1 (endless). These resources also
contain the End Repeat block after the Sound Data block before EOF. There are
other Type values for *.voc files, but TIE doesn't use them.

The sound block is simple. The Divisor has values of 0xA1 to 0xA6 seen, the
Codec is 0x00, and the Length's behaviour is normal.  The sample rate of the
sound is defined as 1MHz / (256 - Divisor), which gets us 10.526-11.111 KHz.

Codec = 00 simply tells us that the sound data is uncompressed 8 bit PCM, which
is easy enough to extract and form a wave file, or if you have a VOC reader,
you can just cut up the LFD and be done with it.

The only trick to the block is the damn 3-byte Length value.

Go, make noises, be free.

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