vdecode.c

#include <stdio.h>
#include "vadpcm.h"

void vdecodeframe(FILE *ifile, s32 *outp, s32 order, s32 ***coefTable)
{
    s32 optimalp;
    s32 scale;
    s32 maxlevel;
    s32 i;
    s32 j;
    s32 in_vec[16];
    s32 ix[16];
    u8 header;
    u8 c;

    maxlevel = 7;
    fread(&header, 1, 1, ifile);
    scale = 1 << (header >> 4);
    optimalp = header & 0xf;

    for (i = 0; i < 16; i += 2)
    {
        fread(&c, 1, 1, ifile);
        ix[i] = c >> 4;
        ix[i + 1] = c & 0xf;

        if (ix[i] <= maxlevel)
        {
            ix[i] *= scale;
        }
        else
        {
            ix[i] = (-0x10 - -ix[i]) * scale;
        }

        if (ix[i + 1] <= maxlevel)
        {
            ix[i + 1] *= scale;
        }
        else
        {
            ix[i + 1] = (-0x10 - -ix[i + 1]) * scale;
        }
    }

    for (j = 0; j < 2; j++)
    {
        for (i = 0; i < 8; i++)
        {
            in_vec[i + order] = ix[j * 8 + i];
        }

        if (j == 0)
        {
            for (i = 0; i < order; i++)
            {
                in_vec[i] = outp[16 - order + i];
            }
        }
        else
        {
            for (i = 0; i < order; i++)
            {
                in_vec[i] = outp[j * 8 - order + i];
            }
        }

        for (i = 0; i < 8; i++)
        {
            outp[i + j * 8] = inner_product(order + 8, coefTable[optimalp][i], in_vec);
        }
    }
}