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Minor info (algorithm verified)

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bnnm 2018-08-03 00:47:54 +02:00
parent e1434bc432
commit d4c0362c30
1 changed files with 4 additions and 4 deletions
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8
src/coding/xmd_decoder.c
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@ -1,7 +1,8 @@
#include "coding.h"
/* Decodes Konami XMD from Xbox games (algorithm info from xmd2wav/xmddecode.dll). */
/* Decodes Konami XMD from Xbox games.
* Algorithm reverse engineered from SH4/CV:CoD's xbe (byte-accurate). */
void decode_xmd(VGMSTREAMCHANNEL * stream, sample * outbuf, int channelspacing, int32_t first_sample, int32_t samples_to_do, size_t frame_size) {
off_t frame_offset;
int i, frames_in, sample_count = 0, samples_done = 0;
@ -42,10 +43,9 @@ void decode_xmd(VGMSTREAMCHANNEL * stream, sample * outbuf, int channelspacing,
new_sample = i&1 ? /* low nibble first */
get_high_nibble_signed(nibbles):
get_low_nibble_signed(nibbles);
new_sample = (new_sample*(scale<<14) + (hist1*0x7298) - (hist2*0x3350)) >> 14;
/* Coefs are similar to XA's filter 2, but using those creates hissing in some songs.
/* Coefs are based on XA's filter 2 (using those creates hissing in some songs though)
* ex. 1.796875 * (1 << 14) = 0x7300, -0.8125 * (1 << 14) = -0x3400 */
//new_sample = (int32_t)(new_sample*scale + hist1*1.796875 + hist2*-0.8125);
new_sample = (new_sample*(scale<<14) + (hist1*0x7298) - (hist2*0x3350)) >> 14;
//new_sample = clamp16(new_sample); /* not needed */
if (sample_count >= first_sample && samples_done < samples_to_do) {