diff options
Diffstat (limited to 'celt/celt_lpc.c')
| -rw-r--r-- | celt/celt_lpc.c | 54 |
1 files changed, 49 insertions, 5 deletions
diff --git a/celt/celt_lpc.c b/celt/celt_lpc.c index 8ecb693e..457e7ed0 100644 --- a/celt/celt_lpc.c +++ b/celt/celt_lpc.c @@ -57,10 +57,10 @@ int p opus_val32 rr = 0; for (j = 0; j < i; j++) rr += MULT32_32_Q31(lpc[j],ac[i - j]); - rr += SHR32(ac[i + 1],3); - r = -frac_div32(SHL32(rr,3), error); + rr += SHR32(ac[i + 1],6); + r = -frac_div32(SHL32(rr,6), error); /* Update LPC coefficients and total error */ - lpc[i] = SHR32(r,3); + lpc[i] = SHR32(r,6); for (j = 0; j < (i+1)>>1; j++) { opus_val32 tmp1, tmp2; @@ -82,8 +82,52 @@ int p } } #ifdef FIXED_POINT - for (i=0;i<p;i++) - _lpc[i] = ROUND16(lpc[i],16); + { + /* Convert the int32 lpcs to int16 and ensure there are no wrap-arounds. + This reuses the logic in silk_LPC_fit() and silk_bwexpander_32(). Any bug + fixes should also be applied there. */ + int iter, idx = 0; + opus_val32 maxabs, absval, chirp_Q16, chirp_minus_one_Q16; + + for (iter = 0; iter < 10; iter++) { + maxabs = 0; + for (i = 0; i < p; i++) { + absval = ABS32(lpc[i]); + if (absval > maxabs) { + maxabs = absval; + idx = i; + } + } + maxabs = PSHR32(maxabs, 13); /* Q25->Q12 */ + + if (maxabs > 32767) { + maxabs = MIN32(maxabs, 163838); + chirp_Q16 = QCONST32(0.999, 16) - DIV32(SHL32(maxabs - 32767, 14), + SHR32(MULT32_32_32(maxabs, idx + 1), 2)); + chirp_minus_one_Q16 = chirp_Q16 - 65536; + + /* Apply bandwidth expansion. */ + for (i = 0; i < p - 1; i++) { + lpc[i] = MULT32_32_Q16(chirp_Q16, lpc[i]); + chirp_Q16 += PSHR32(MULT32_32_32(chirp_Q16, chirp_minus_one_Q16), 16); + } + lpc[p - 1] = MULT32_32_Q16(chirp_Q16, lpc[p - 1]); + } else { + break; + } + } + + if (iter == 10) { + /* If the coeffs still do not fit into the 16 bit range after 10 iterations, + fall back to the A(z)=1 filter. */ + OPUS_CLEAR(lpc, p); + _lpc[0] = 4096; /* Q12 */ + } else { + for (i = 0; i < p; i++) { + _lpc[i] = EXTRACT16(PSHR32(lpc[i], 13)); /* Q25->Q12 */ + } + } + } #endif } |