void ff_celp_lp_synthesis_filterf(float *out, const float *filter_coeffs, const float* in, int buffer_length, int filter_length) { int i,n; #if 0 // Unoptimized code path for improved readability for (n = 0; n < buffer_length; n++) { out[n] = in[n]; for (i = 1; i <= filter_length; i++) out[n] -= filter_coeffs[i-1] * out[n-i]; } #else float out0, out1, out2, out3; float old_out0, old_out1, old_out2, old_out3; float a,b,c; a = filter_coeffs[0]; b = filter_coeffs[1]; c = filter_coeffs[2]; b -= filter_coeffs[0] * filter_coeffs[0]; c -= filter_coeffs[1] * filter_coeffs[0]; c -= filter_coeffs[0] * b; old_out0 = out[-4]; old_out1 = out[-3]; old_out2 = out[-2]; old_out3 = out[-1]; for (n = 0; n <= buffer_length - 4; n+=4) { float tmp0,tmp1,tmp2; float val; out0 = in[0]; out1 = in[1]; out2 = in[2]; out3 = in[3]; out0 -= filter_coeffs[2] * old_out1; out1 -= filter_coeffs[2] * old_out2; out2 -= filter_coeffs[2] * old_out3; out0 -= filter_coeffs[1] * old_out2; out1 -= filter_coeffs[1] * old_out3; out0 -= filter_coeffs[0] * old_out3; val = filter_coeffs[3]; out0 -= val * old_out0; out1 -= val * old_out1; out2 -= val * old_out2; out3 -= val * old_out3; for (i = 5; i <= filter_length; i += 2) { old_out3 = out[-i]; val = filter_coeffs[i-1]; out0 -= val * old_out3; out1 -= val * old_out0; out2 -= val * old_out1; out3 -= val * old_out2; old_out2 = out[-i-1]; val = filter_coeffs[i]; out0 -= val * old_out2; out1 -= val * old_out3; out2 -= val * old_out0; out3 -= val * old_out1; FFSWAP(float, old_out0, old_out2); old_out1 = old_out3; } tmp0 = out0; tmp1 = out1; tmp2 = out2; out3 -= a * tmp2; out2 -= a * tmp1; out1 -= a * tmp0; out3 -= b * tmp1; out2 -= b * tmp0; out3 -= c * tmp0; out[0] = out0; out[1] = out1; out[2] = out2; out[3] = out3; old_out0 = out0; old_out1 = out1; old_out2 = out2; old_out3 = out3; out += 4; in += 4; } out -= n; in -= n; for (; n < buffer_length; n++) { out[n] = in[n]; for (i = 1; i <= filter_length; i++) out[n] -= filter_coeffs[i-1] * out[n-i]; } #endif }