ilog
The "ilog(x)" function returns the position number (1 through n) of the highest set bit in the two's complement integer value
[x]. Values of [x] less than zero are defined to return zero.
1) [return_value] = 0;
2) if ( [x] is greater than zero ){
3) increment [return_value];
4) logical shift [x] one bit to the right, padding the MSb with zero
5) repeat at step 2)
}
6) done
Examples:
1) [mantissa] = [x] bitwise AND 0x1fffff (unsigned result) 2) [sign] = [x] bitwise AND 0x80000000 (unsigned result) 3) [exponent] = ( [x] bitwise AND 0x7fe00000) shifted right 21 bits (unsigned result) 4) if ( [sign] is nonzero ) then negate [mantissa] 5) return [mantissa] * ( 2 ^ ( [exponent] - 788 ) )
The return value for this function is defined to be 'the greatest
integer value for which [return_value] to the power of
[codebook_dimensions] is less than or equal to
[codebook_entries]'.
low_neighbor
"low_neighbor(v,x)" finds the position n in vector [v] of
the greatest value scalar element for which n is less than
[x] and vector [v] element n is less
than vector [v] element [x].
high_neighbor
"high_neighbor(v,x)" finds the position n in vector [v] of
the lowest value scalar element for which n is less than
[x] and vector [v] element n is greater
than vector [v] element [x].
render_point
"render_point(x0,y0,x1,y1,X)" is used to find the Y value at point X
along the line specified by x0, x1, y0 and y1. This function uses an
integer algorithm to solve for the point directly without calculating
intervening values along the line.
1) [dy] = [y1] - [y0]
2) [adx] = [x1] - [x0]
3) [ady] = absolute value of [dy]
4) [err] = [ady] * ([X] - [x0])
5) [off] = [err] / [adx] using integer division
6) if ( [dy] is less than zero ) {
7) [Y] = [y0] - [off]
} else {
8) [Y] = [y0] + [off]
}
9) done
1) [dy] = [y1] - [y0]
2) [adx] = [x1] - [x0]
3) [ady] = absolute value of [dy]
4) [base] = [dy] / [adx] using integer division
5) [x] = [x0]
6) [y] = [y0]
7) [err] = 0
8) if ( [dy] is less than 0 ) {
9) [sy] = [base] - 1
} else {
10) [sy] = [base] + 1
}
11) [ady] = [ady] - (absolute value of [base]) * [adx]
12) vector [v] element [x] = [y]
13) iterate [x] over the range [x0]+1 ... [x1]-1 {
14) [err] = [err] + [ady];
15) if ( [err] >= [adx] ) {
15) [err] = [err] - [adx]
16) [y] = [y] + [sy]
} else {
17) [y] = [y] + [base]
}
18) vector [v] element [x] = [y]
}
Ogg is a Xiph.org Foundation effort
to protect essential tenets of Internet multimedia from corporate
hostage-taking; Open Source is the net's greatest tool to keep
everyone honest. See About
the Xiph.org Foundation for details.
Ogg Vorbis is the first Ogg audio CODEC. Anyone may freely use and distribute the Ogg and Vorbis specification, whether in a private, public or corporate capacity. However, the Xiph.org Foundation and the Ogg project (xiph.org) reserve the right to set the Ogg Vorbis specification and certify specification compliance.
Xiph.org's Vorbis software CODEC implementation is distributed under a BSD-like license. This does not restrict third parties from distributing independent implementations of Vorbis software under other licenses.
Ogg, Vorbis, Xiph.org Foundation and their logos are trademarks (tm) of the Xiph.org Foundation. These pages are copyright (C) 1994-2002 Xiph.org Foundation. All rights reserved.