wiki:SV8Specification

Version 2 (modified by r2d, 15 years ago) (diff)

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SV8 specification draft

File header

Field length (bits) Value
Magic 24 "MP+"
Version 8 0x08

This file header allow old mpc readers to stop decoding at this point, without crashing.

Block formating

All blocks are formated using Key / Length / Value.
Key is 16 bits long. It's the block ID.
Length is a variable size field using the same values as matroska :

bits, big-endian
1xxx xxxx                                           - value 0 to  2^7-2
01xx xxxx  xxxx xxxx                                - value 0 to 2^14-2
001x xxxx  xxxx xxxx  xxxx xxxx                     - value 0 to 2^21-2
0001 xxxx  xxxx xxxx  xxxx xxxx  xxxx xxxx          - value 0 to 2^28-2
...

The length is the size of the block in bytes, including the key and size fields. So the minimum length of a block is 3 bytes.
The value is the block content. Its size can be 0.
All unused bits in a block MUST be 0.

Field length (bits) Value
Key 16 "EX"
Length n*8; 0 < n < 9 0x1A
Value Lentgh * 8 "exemple"

Stream information block

This block key is "SI".
This block contain the informations needed to decode the stream. This block is mandatory and must be written before the first audio block.

Field length (bits) Value comment
CRC 32 CRC 32 of the block (this field excluded). 0 = invalid
Sample count n*8; 0 < n < 9 number of samples in the stream. 0 = unknow
Max used bands 4 maximum number of bands used in the file
Sample Frequency 4 see table below
Channel count 4 number of channels in the stream
Audio block frames 4 1..16 number of frames in an audio block is : 2Value
IS used 1 Klemm specification suggest to use the number of band always using IS ?
MS used 1
True gapless 1 always 1 ?
PNS used 1
unused 4 must be 0

Frequency table

Value Frequency (Hz)
0 44100
1 48000
2 37800
3 32000
4 96000

The CRC used in this block needs to be define.

Replay gain block

This block key is "RG".
This block contains replay gain datas. If this block exists, it must be written before the first audio block.
A log scale must be used to store the values.

Field length (bits) Value comment
Title gain 16 The loudness calculated for the title, and not the gain that the player must apply
Title peak 16
Album gain 16 The loudness calculated for the album
Album peak 16
Version 8 The replay gain version

Encoder infomations

This block key is "EI".

Field length (bits) Value comment
profile used 4 0..15
unused 4
encoder version 8
 Encoder version * 100  (106 = 1.06)
 EncoderVersion % 10 == 0        Release (1.0)
 EncoderVersion %  2 == 0        Beta (1.06)
 EncoderVersion %  2 == 1        Alpha (1.05a...z)

Audio block

This block key is "AB".
This block contain audio frames. The first frame is a key frame.
The seek elements allow to jump back or forward. The block size can be used to seek 1 block forward.

Seek block nb should be ( - means offset is negative) :
2 -2 3 -3 2 -2 4 -4 2 -2 3 -3 2 -2 5 -5 2 -2 3 -3 2 -2 4 -4 2 -2 3 -3 6 -6 2 -2 ...
so 2 -> 2, 3 -> 3 ... and -2 -> -2, -3 -> -3 ...
Allow to seek back and forward in O(ln(n)) time without a seeking table.

Field length (bits) Value comment
seek block nb 4 2..17 the number of blocks that can be skiped is 2Value
seek offset 28 -227..227-1 number of bytes to jump the blocks from the beginning of this block. 0 = invalid
audio frames ?

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