#include "coding.h" #include "../util.h" #if 0 /* known game code/platforms use float buffer and coefs, but some approximations around use this int math: * ... * coef1 = table[index + 0] * coef2 = table[index + 4] * sample = clamp16(((signed_nibble << (20 - shift)) + hist1 * coef1 + hist2 * coef2 + 128) >> 8); */ static const int EA_XA_TABLE[20] = { 0, 240, 460, 392, 0, 0, -208, -220, 0, 1, 3, 4, 7, 8, 10, 11, 0, -1, -3, -4 }; #endif /* standard CD-XA's K0/K1 filter pairs */ static const float xa_coefs[16][2] = { { 0.0, 0.0 }, { 0.9375, 0.0 }, { 1.796875, -0.8125 }, { 1.53125, -0.859375 }, /* only 4 pairs exist, assume 0s for bad indexes */ }; /* EA-XAS (XA Seekable) Version 1, evolution of EA-XA/XAS and cousin of MTA2. Reverse engineered from various .exes/.so * * Layout: blocks of 0x4c per channel (128 samples), divided into 4 headers + 4 vertical groups of 15 bytes. * Original code reads all headers first then processes all nibbles (for CPU cache/parallelism/SIMD optimizations). * To simplify, always decodes the block and discards unneeded samples, so doesn't use external hist. */ void decode_ea_xas_v1(VGMSTREAMCHANNEL* stream, sample_t* outbuf, int channelspacing, int32_t first_sample, int32_t samples_to_do, int channel) { uint8_t frame[0x4c] = {0}; off_t frame_offset; int group, row, i, samples_done = 0, sample_count = 0; size_t bytes_per_frame, samples_per_frame; /* internal interleave */ bytes_per_frame = 0x4c; samples_per_frame = 128; first_sample = first_sample % samples_per_frame; frame_offset = stream->offset + bytes_per_frame * channel; read_streamfile(frame, frame_offset, bytes_per_frame, stream->streamfile); /* ignore EOF errors */ //todo: original code uses float sample buffer: //- header pcm-hist to float-hist: hist * (1/32768) //- nibble to signed to float: (int32_t)(pnibble << 28) * SHIFT_MUL_LUT[shift_index] // look-up table just simplifies ((nibble << 12 << 12) >> 12 + shift) * (1/32768) // though maybe introduces rounding errors? //- coefs apply normally, though hists are already floats //- final float sample isn't clamped /* parse group headers */ for (group = 0; group < 4; group++) { float coef1, coef2; int16_t hist1, hist2; uint8_t shift; uint32_t group_header = (uint32_t)get_32bitLE(frame + group*0x4); /* always LE */ coef1 = xa_coefs[group_header & 0x0F][0]; coef2 = xa_coefs[group_header & 0x0F][1]; hist2 = (int16_t)((group_header >> 0) & 0xFFF0); hist1 = (int16_t)((group_header >> 16) & 0xFFF0); shift = (group_header >> 16) & 0x0F; /* write header samples (needed) */ if (sample_count >= first_sample && samples_done < samples_to_do) { outbuf[samples_done * channelspacing] = hist2; samples_done++; } sample_count++; if (sample_count >= first_sample && samples_done < samples_to_do) { outbuf[samples_done * channelspacing] = hist1; samples_done++; } sample_count++; /* process nibbles per group */ for (row = 0; row < 15; row++) { for (i = 0; i < 1*2; i++) { uint8_t nibbles = frame[4*4 + row*0x04 + group + i/2]; int sample; sample = i&1 ? /* high nibble first */ (nibbles >> 0) & 0x0f : (nibbles >> 4) & 0x0f; sample = (int16_t)(sample << 12) >> shift; /* 16b sign extend + scale */ sample = sample + hist1 * coef1 + hist2 * coef2; sample = clamp16(sample); if (sample_count >= first_sample && samples_done < samples_to_do) { outbuf[samples_done * channelspacing] = sample; samples_done++; } sample_count++; hist2 = hist1; hist1 = sample; } } } /* internal interleave (interleaved channels, but manually advances to co-exist with ea blocks) */ if (first_sample + samples_done == samples_per_frame) { stream->offset += bytes_per_frame * channelspacing; } } /* EA-XAS v0 (xas0), without complex layouts and closer to EA-XA. Somewhat based on daemon1's decoder. */ void decode_ea_xas_v0(VGMSTREAMCHANNEL * stream, sample * outbuf, int channelspacing, int32_t first_sample, int32_t samples_to_do) { uint8_t frame[0x13] = {0}; off_t frame_offset; int i, frames_in, samples_done = 0, sample_count = 0; size_t bytes_per_frame, samples_per_frame; /* external interleave (fixed size), mono */ bytes_per_frame = 0x02 + 0x02 + 0x0f; samples_per_frame = 1 + 1 + 0x0f*2; frames_in = first_sample / samples_per_frame; first_sample = first_sample % samples_per_frame; frame_offset = stream->offset + bytes_per_frame * frames_in; read_streamfile(frame, frame_offset, bytes_per_frame, stream->streamfile); /* ignore EOF errors */ //todo see above /* process frame */ { float coef1, coef2; int16_t hist1, hist2; uint8_t shift; uint32_t frame_header = (uint32_t)get_32bitLE(frame); /* always LE */ coef1 = xa_coefs[frame_header & 0x0F][0]; coef2 = xa_coefs[frame_header & 0x0F][1]; hist2 = (int16_t)((frame_header >> 0) & 0xFFF0); hist1 = (int16_t)((frame_header >> 16) & 0xFFF0); shift = (frame_header >> 16) & 0x0F; /* write header samples (needed) */ if (sample_count >= first_sample && samples_done < samples_to_do) { outbuf[samples_done * channelspacing] = hist2; samples_done++; } sample_count++; if (sample_count >= first_sample && samples_done < samples_to_do) { outbuf[samples_done * channelspacing] = hist1; samples_done++; } sample_count++; /* process nibbles */ for (i = 0; i < 0x0f*2; i++) { uint8_t nibbles = frame[0x02 + 0x02 + i/2]; int sample; sample = i&1 ? /* high nibble first */ (nibbles >> 0) & 0x0f : (nibbles >> 4) & 0x0f; sample = (int16_t)(sample << 12) >> shift; /* 16b sign extend + scale */ sample = sample + hist1 * coef1 + hist2 * coef2; sample = clamp16(sample); if (sample_count >= first_sample && samples_done < samples_to_do) { outbuf[samples_done * channelspacing] = sample; samples_done++; } sample_count++; hist2 = hist1; hist1 = sample; } } }