vgmstream/src/coding/adx_decoder.c

#include "adx.h"
#include "../util.h"

void decode_adx(VGMSTREAMCHANNEL * stream, sample * outbuf, int channelspacing, int32_t first_sample, int32_t samples_to_do) {
    int i;
    int32_t sample_count;

    int framesin = first_sample/32;

    int32_t scale = read_16bitBE(stream->offset+framesin*18,stream->streamfile) + 1;
    int32_t hist1 = stream->adpcm_history1_32;
    int32_t hist2 = stream->adpcm_history2_32;
    int coef1 = stream->adpcm_coef[0];
    int coef2 = stream->adpcm_coef[1];

    first_sample = first_sample%32;

    for (i=first_sample,sample_count=0; i<first_sample+samples_to_do; i++,sample_count+=channelspacing) {
        int sample_byte = read_8bit(stream->offset+framesin*18+2+i/2,stream->streamfile);

        outbuf[sample_count] = clamp16(
                (i&1?
                 get_low_nibble_signed(sample_byte):
                 get_high_nibble_signed(sample_byte)
                ) * scale +
                ((coef1 * hist1 + coef2 * hist2) >> 12)
                );

        hist2 = hist1;
        hist1 = outbuf[sample_count];
    }

    stream->adpcm_history1_32 = hist1;
    stream->adpcm_history2_32 = hist2;
}