Cool_Tools/vgmstream
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This commit is contained in:
bnnm 2023-02-05 22:22:50 +01:00
parent e3ad99925a
commit 516fdd7d76
1 changed files with 10 additions and 3 deletions
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13
src/coding/sdx2_decoder.c
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@ -3,7 +3,11 @@
#include "../util.h"
/* SDX2 - 2:1 Squareroot-delta-exact compression */
/* CBD2 - 2:1 Cuberoot-delta-exact compression (from the unreleased 3DO M2) */
/* CBD2 - 2:1 Cuberoot-delta-exact compression (from 3DO/Konami M2) */
/* Original code is implemented with ops in a custom DSP (DSPP) with a variation of FORTH
* (rather than tables), in the "3DO M2 Portfolio OS", so could be converted to plain calcs. */
/* for (i=-128;i<128;i++) { squares[i+128] = i<0?(-i*i)*2:(i*i)*2; } */
static int16_t squares[256] = {
@ -34,6 +38,7 @@ static int16_t squares[256] = {
};
/*
// original DSP ops, seems equivalent to (i * i * i) / 64
for (uint16_t i = 0; i < 0x100; i += 1) {
int16_t v = i;
v -= 0x80;
@ -83,7 +88,8 @@ static void decode_delta_exact(VGMSTREAMCHANNEL * stream, sample_t * outbuf, int
int8_t sample_byte = read_8bit(stream->offset+i,stream->streamfile);
int16_t sample;
if (!(sample_byte & 1)) hist = 0;
if (!(sample_byte & 1)) /* even: "exact mode" (value as-is), odd: "delta mode" */
hist = 0;
sample = hist + table[sample_byte+128];
hist = outbuf[sample_count] = clamp16(sample);
@ -102,7 +108,8 @@ static void decode_delta_exact_int(VGMSTREAMCHANNEL * stream, sample_t * outbuf,
int8_t sample_byte = read_8bit(stream->offset+i*channelspacing,stream->streamfile);
int16_t sample;
if (!(sample_byte & 1)) hist = 0;
if (!(sample_byte & 1)) /* even: "exact mode" (value as-is), odd: "delta mode" */
hist = 0;
sample = hist + table[sample_byte+128];
hist = outbuf[sample_count] = clamp16(sample);