diff options
Diffstat (limited to 'celt/bands.c')
| -rw-r--r-- | celt/bands.c | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/celt/bands.c b/celt/bands.c index 05205554..20d1fd5e 100644 --- a/celt/bands.c +++ b/celt/bands.c @@ -684,6 +684,7 @@ struct band_ctx { int arch; int theta_round; int disable_inv; + int avoid_split_noise; }; struct split_ctx { @@ -745,6 +746,20 @@ static void compute_theta(struct band_ctx *ctx, struct split_ctx *sctx, if (!stereo || ctx->theta_round == 0) { itheta = (itheta*(opus_int32)qn+8192)>>14; + if (!stereo && ctx->avoid_split_noise && itheta > 0 && itheta < qn) + { + /* Check if the selected value of theta will cause the bit allocation + to inject noise on one side. If so, make sure the energy of that side + is zero. */ + int unquantized = celt_udiv((opus_int32)itheta*16384, qn); + imid = bitexact_cos((opus_int16)unquantized); + iside = bitexact_cos((opus_int16)(16384-unquantized)); + delta = FRAC_MUL16((N-1)<<7,bitexact_log2tan(iside,imid)); + if (delta > *b) + itheta = qn; + else if (delta < -*b) + itheta = 0; + } } else { int down; /* Bias quantization towards itheta=0 and itheta=16384. */ @@ -1452,6 +1467,8 @@ void quant_all_bands(int encode, const CELTMode *m, int start, int end, ctx.disable_inv = disable_inv; ctx.resynth = resynth; ctx.theta_round = 0; + /* Avoid injecting noise in the first band on transients. */ + ctx.avoid_split_noise = B > 1; for (i=start;i<end;i++) { opus_int32 tell; @@ -1640,6 +1657,9 @@ void quant_all_bands(int encode, const CELTMode *m, int start, int end, /* Update the folding position only as long as we have 1 bit/sample depth. */ update_lowband = b>(N<<BITRES); + /* We only need to avoid noise on a split for the first band. After that, we + have folding. */ + ctx.avoid_split_noise = 0; } *seed = ctx.seed; |