fix bug where LP was tried even if autoc[0]==0.0

diff --git a/src/libFLAC/encoder.c b/src/libFLAC/encoder.c
index 27bfc32b5e60c73c51f237e70e79b9b7b893d7f6..6208934922940e4924bf592a5696503d1ef5b8aa 100644 (file)
--- a/src/libFLAC/encoder.c
+++ b/src/libFLAC/encoder.c
@@ -871,35 +871,38 @@ bool encoder_process_subframe_(FLAC__Encoder *encoder, unsigned max_partition_or
                                        max_lpc_order = encoder->max_lpc_order;
                                if(max_lpc_order > 0) {
                                        FLAC__lpc_compute_autocorrelation(real_signal, frame_header->blocksize, max_lpc_order+1, autoc);
-                                       FLAC__lpc_compute_lp_coefficients(autoc, max_lpc_order, lp_coeff, lpc_error);
-                                       if(encoder->do_exhaustive_model_search) {
-                                               min_lpc_order = 1;
-                                       }
-                                       else {
-                                               unsigned guess_lpc_order = FLAC__lpc_compute_best_order(lpc_error, max_lpc_order, frame_header->blocksize, bits_per_sample);
-                                               min_lpc_order = max_lpc_order = guess_lpc_order;
-                                       }
-                                       if(encoder->do_qlp_coeff_prec_search) {
-                                               min_qlp_coeff_precision = FLAC__MIN_QLP_COEFF_PRECISION;
-                                               max_qlp_coeff_precision = min(32 - bits_per_sample - 1, (1u<<FLAC__SUBFRAME_LPC_QLP_COEFF_PRECISION_LEN)-1);
-                                       }
-                                       else {
-                                               min_qlp_coeff_precision = max_qlp_coeff_precision = encoder->qlp_coeff_precision;
-                                       }
-                                       for(lpc_order = min_lpc_order; lpc_order <= max_lpc_order; lpc_order++) {
-                                               lpc_residual_bits_per_sample = FLAC__lpc_compute_expected_bits_per_residual_sample(lpc_error[lpc_order-1], frame_header->blocksize-lpc_order);
-                                               if(lpc_residual_bits_per_sample >= (real)bits_per_sample)
-                                                       continue; /* don't even try */
-                                               rice_parameter = (lpc_residual_bits_per_sample > 0.0)? (unsigned)(lpc_residual_bits_per_sample+0.5) : 0; /* 0.5 is for rounding */
-                                               rice_parameter++; /* to account for the signed->unsigned conversion during rice coding */
-                                               if(rice_parameter >= (1u << FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE_PARAMETER_LEN))
-                                                       rice_parameter = (1u << FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE_PARAMETER_LEN) - 1;
-                                               for(qlp_coeff_precision = min_qlp_coeff_precision; qlp_coeff_precision <= max_qlp_coeff_precision; qlp_coeff_precision++) {
-                                                       _candidate_bits = encoder_evaluate_lpc_subframe_(integer_signal, residual[!_best_subframe], encoder->guts->abs_residual, lp_coeff[lpc_order-1], frame_header->blocksize, bits_per_sample, lpc_order, qlp_coeff_precision, rice_parameter, max_partition_order, subframe[!_best_subframe]);
-                                                       if(_candidate_bits > 0) { /* if == 0, there was a problem quantizing the lpcoeffs */
-                                                               if(_candidate_bits < _best_bits) {
-                                                                       _best_subframe = !_best_subframe;
-                                                                       _best_bits = _candidate_bits;
+                                       /* if autoc[0] == 0.0, the signal is constant and we usually won't get here, but it can happen */
+                                       if(autoc[0] != 0.0) {
+                                               FLAC__lpc_compute_lp_coefficients(autoc, max_lpc_order, lp_coeff, lpc_error);
+                                               if(encoder->do_exhaustive_model_search) {
+                                                       min_lpc_order = 1;
+                                               }
+                                               else {
+                                                       unsigned guess_lpc_order = FLAC__lpc_compute_best_order(lpc_error, max_lpc_order, frame_header->blocksize, bits_per_sample);
+                                                       min_lpc_order = max_lpc_order = guess_lpc_order;
+                                               }
+                                               if(encoder->do_qlp_coeff_prec_search) {
+                                                       min_qlp_coeff_precision = FLAC__MIN_QLP_COEFF_PRECISION;
+                                                       max_qlp_coeff_precision = min(32 - bits_per_sample - 1, (1u<<FLAC__SUBFRAME_LPC_QLP_COEFF_PRECISION_LEN)-1);
+                                               }
+                                               else {
+                                                       min_qlp_coeff_precision = max_qlp_coeff_precision = encoder->qlp_coeff_precision;
+                                               }
+                                               for(lpc_order = min_lpc_order; lpc_order <= max_lpc_order; lpc_order++) {
+                                                       lpc_residual_bits_per_sample = FLAC__lpc_compute_expected_bits_per_residual_sample(lpc_error[lpc_order-1], frame_header->blocksize-lpc_order);
+                                                       if(lpc_residual_bits_per_sample >= (real)bits_per_sample)
+                                                               continue; /* don't even try */
+                                                       rice_parameter = (lpc_residual_bits_per_sample > 0.0)? (unsigned)(lpc_residual_bits_per_sample+0.5) : 0; /* 0.5 is for rounding */
+                                                       rice_parameter++; /* to account for the signed->unsigned conversion during rice coding */
+                                                       if(rice_parameter >= (1u << FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE_PARAMETER_LEN))
+                                                               rice_parameter = (1u << FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE_PARAMETER_LEN) - 1;
+                                                       for(qlp_coeff_precision = min_qlp_coeff_precision; qlp_coeff_precision <= max_qlp_coeff_precision; qlp_coeff_precision++) {
+                                                               _candidate_bits = encoder_evaluate_lpc_subframe_(integer_signal, residual[!_best_subframe], encoder->guts->abs_residual, lp_coeff[lpc_order-1], frame_header->blocksize, bits_per_sample, lpc_order, qlp_coeff_precision, rice_parameter, max_partition_order, subframe[!_best_subframe]);
+                                                               if(_candidate_bits > 0) { /* if == 0, there was a problem quantizing the lpcoeffs */
+                                                                       if(_candidate_bits < _best_bits) {
+                                                                               _best_subframe = !_best_subframe;
+                                                                               _best_bits = _candidate_bits;
+                                                                       }
                                                                }
                                                        }
                                                }