/* Compute inverse MDCT of size N = 2^nbits  */
void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input)
/* Compute inverse MDCT of size N = 2^nbits  */
void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input)
{
    int k;
    int n = 1 << s->mdct_bits;
    int n2 = n >> 1;
    int n4 = n >> 2;
    ff_imdct_half_c(s, output+n4, input);
    for(k = 0; k < n4; k++) {
        output[k] = -output[n2-k-1];
        output[n-k-1] = output[n2+k];
    }
}