diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/libFLAC/include/private/lpc.h | 14 | ||||
| -rw-r--r-- | src/libFLAC/lpc.c | 68 |
2 files changed, 69 insertions, 13 deletions
diff --git a/src/libFLAC/include/private/lpc.h b/src/libFLAC/include/private/lpc.h index f5b86e11..069d4593 100644 --- a/src/libFLAC/include/private/lpc.h +++ b/src/libFLAC/include/private/lpc.h @@ -71,15 +71,15 @@ void FLAC__lpc_compute_lp_coefficients(const real autoc[], unsigned max_order, r * bit) of largest coefficient * IN bits_per_sample > 0 bits per sample of the originial signal * OUT qlp_coeff[0,order-1] quantized coefficients - * OUT bits # of bits to shift right to get approximated - * LP coefficients. NOTE: could be negative, - * but |*bits| will always be <= precision + * OUT shift # of bits to shift right to get approximated + * LP coefficients. NOTE: could be negative. * RETURN 0 => quantization OK - * 1 => coefficients vary too much to quantize to the desired - * precision. 'bits' is unset - * 2 => coefficients are all zero, which is bad. 'bits' is unset + * 1 => coefficients require too much shifting for *shift to + * fit in the LPC subframe header. 'shift' is unset. + * 2 => coefficients are all zero, which is bad. 'shift' is + * unset. */ -int FLAC__lpc_quantize_coefficients(const real lp_coeff[], unsigned order, unsigned precision, unsigned bits_per_sample, int32 qlp_coeff[], int *bits); +int FLAC__lpc_quantize_coefficients(const real lp_coeff[], unsigned order, unsigned precision, unsigned bits_per_sample, int32 qlp_coeff[], int *shift); /* * FLAC__lpc_compute_residual_from_qlp_coefficients() diff --git a/src/libFLAC/lpc.c b/src/libFLAC/lpc.c index 1e7a6a97..27cfc4b8 100644 --- a/src/libFLAC/lpc.c +++ b/src/libFLAC/lpc.c @@ -80,7 +80,8 @@ void FLAC__lpc_compute_lp_coefficients(const real autoc[], unsigned max_order, r } } -int FLAC__lpc_quantize_coefficients(const real lp_coeff[], unsigned order, unsigned precision, unsigned bits_per_sample, int32 qlp_coeff[], int *bits) +#if 0 +int FLAC__lpc_quantize_coefficients(const real lp_coeff[], unsigned order, unsigned precision, unsigned bits_per_sample, int32 qlp_coeff[], int *shift) { unsigned i; real d, rprecision = (real)precision, maxlog = -1e99, minlog = 1e99; @@ -109,15 +110,70 @@ int FLAC__lpc_quantize_coefficients(const real lp_coeff[], unsigned order, unsig else if((rprecision-1.0) - maxlog >= (real)(precision+1)) rprecision = (real)precision + maxlog + 1.0; - *bits = (int)floor((rprecision-1.0) - maxlog); /* '-1' because bits can be negative and the sign bit costs 1 bit */ - if(*bits > (int)precision || *bits <= -(int)precision) { - fprintf(stderr, "@@@ FLAC__lpc_quantize_coefficients(): ERROR: *bits=%d, maxlog=%f, minlog=%f, precision=%u, rprecision=%f\n", *bits, maxlog, minlog, precision, rprecision); + *shift = (int)floor((rprecision-1.0) - maxlog); /* '-1' because *shift can be negative and the sign bit costs 1 bit */ + if(*shift > (int)precision || *shift <= -(int)precision) { + fprintf(stderr, "@@@ FLAC__lpc_quantize_coefficients(): ERROR: *shift=%d, maxlog=%f, minlog=%f, precision=%u, rprecision=%f\n", *shift, maxlog, minlog, precision, rprecision); return 1; } - if(*bits != 0) { /* just to avoid wasting time... */ + if(*shift != 0) { /* just to avoid wasting time... */ for(i = 0; i < order; i++) - qlp_coeff[i] = (int32)floor(lp_coeff[i] * (real)(1 << *bits)); + qlp_coeff[i] = (int32)floor(lp_coeff[i] * (real)(1 << *shift)); + } + return 0; +} +#endif + +int FLAC__lpc_quantize_coefficients(const real lp_coeff[], unsigned order, unsigned precision, unsigned bits_per_sample, int32 qlp_coeff[], int *shift) +{ + unsigned i; + real d, cmax = -1e99;//@@@, cmin = 1e99; + + assert(bits_per_sample > 0); + assert(bits_per_sample <= sizeof(int32)*8); + assert(precision > 0); + assert(precision >= FLAC__MIN_QLP_COEFF_PRECISION); + assert(precision + bits_per_sample < sizeof(int32)*8); +#ifdef NDEBUG + (void)bits_per_sample; /* silence compiler warning about unused parameter */ +#endif + + /* drop one bit for the sign; from here on out we consider only |lp_coeff[i]| */ + precision--; + + for(i = 0; i < order; i++) { + if(lp_coeff[i] == 0.0) + continue; + d = fabs(lp_coeff[i]); + if(d > cmax) + cmax = d; +//@@@ if(d < cmin) +//@@@ cmin = d; + } +//@@@ if(cmax < cmin) + if(cmax < 0) { + /* => coeffients are all 0, which means our constant-detect didn't work */ +fprintf(stderr,"@@@ LPCQ ERROR, all lpc_coeffs are 0\n"); + return 2; + } + else { +//@@@ const int minshift = (int)precision - floor(log(cmin) / M_LN2) - 1; + const int maxshift = (int)precision - floor(log(cmax) / M_LN2) - 1; +//@@@ assert(maxshift >= minshift); + const int max_shiftlimit = (1 << (FLAC__SUBFRAME_LPC_QLP_SHIFT_LEN-1)) - 1; + const int min_shiftlimit = -max_shiftlimit - 1; + + *shift = maxshift; + + if(*shift < min_shiftlimit || *shift > max_shiftlimit) { +fprintf(stderr,"@@@ LPCQ ERROR, shift is outside shiftlimit\n"); + return 1; + } + } + + if(*shift != 0) { /* just to avoid wasting time... */ + for(i = 0; i < order; i++) + qlp_coeff[i] = (int32)floor(lp_coeff[i] * (real)(1 << *shift)); } return 0; } |