improve the rice parameter calculation

diff --git a/src/libFLAC/stream_encoder.c b/src/libFLAC/stream_encoder.c
index 14ea34e..7e22441 100644 (file)
--- a/src/libFLAC/stream_encoder.c
+++ b/src/libFLAC/stream_encoder.c
@@ -1671,17 +1671,19 @@ FLAC__bool stream_encoder_set_partitioned_rice_(const FLAC__uint32 abs_residual[
                                else
                                        partition_samples -= predictor_order;
                        }
-                       mean = partition_samples >> 1;
 #ifdef FLAC__PRECOMPUTE_PARTITION_SUMS
-                       mean += abs_residual_partition_sums[partition];
+                       mean = abs_residual_partition_sums[partition];
 #else
+                       mean = 0;
                        save_residual_sample = residual_sample;
                        for(partition_sample = 0; partition_sample < partition_samples; residual_sample++, partition_sample++)
                                mean += abs_residual[residual_sample];
                        residual_sample = save_residual_sample;
 #endif
-                       mean /= partition_samples;
 #ifdef FLAC__SYMMETRIC_RICE
+                       mean += partition_samples >> 1; /* for rounding effect */
+                       mean /= partition_samples;
+
                        /* calc rice_parameter = floor(log2(mean)) */
                        rice_parameter = 0;
                        mean>>=1;
@@ -1690,12 +1692,9 @@ FLAC__bool stream_encoder_set_partitioned_rice_(const FLAC__uint32 abs_residual[
                                mean >>= 1;
                        }
 #else
-                       /* calc rice_parameter = floor(log2(mean)) + 1 */
-                       rice_parameter = 0;
-                       while(mean) {
-                               rice_parameter++;
-                               mean >>= 1;
-                       }
+                       /* calc rice_parameter ala LOCO-I */
+                       for(rice_parameter = 0; (partition_samples<<rice_parameter) < mean; rice_parameter++)
+                               ;
 #endif
                        if(rice_parameter >= FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE_ESCAPE_PARAMETER)
                                rice_parameter = FLAC__ENTROPY_CODING_METHOD_PARTITIONED_RICE_ESCAPE_PARAMETER - 1;