shithub: opus

Download patch

ref: eb1759736f03bb171907b5d31da9ca135f7c21e5
parent: bbb4cf554c3a892a9245dd684b225d1ff1651da7
author: Jean-Marc Valin <jmvalin@amazon.com>
date: Sun Jul 9 09:06:58 EDT 2023 

Some general SILK CBR tuning

The gain*2 when overshooting was too aggressive and the undershoot
case wasn't aggressive enough. This now seems to work reasonably well.


--- a/silk/fixed/encode_frame_FIX.c
+++ b/silk/fixed/encode_frame_FIX.c
@@ -318,17 +318,10 @@
             if( ( found_lower & found_upper ) == 0 ) {
                 /* Adjust gain according to high-rate rate/distortion curve */
                 if( nBits > maxBits ) {
-                    if (gainMult_Q8 < 16384) {
-                        gainMult_Q8 *= 2;
-                    } else {
-                        gainMult_Q8 = 32767;
-                    }
+                    gainMult_Q8 = silk_min_32( 1024, gainMult_Q8*3/2 );
                 } else {
-                    opus_int32 gain_factor_Q16;
-                    gain_factor_Q16 = silk_log2lin( silk_LSHIFT( nBits - maxBits, 7 ) / psEnc->sCmn.frame_length + SILK_FIX_CONST( 16, 7 ) );
-                    gainMult_Q8 = silk_SMULWB( gain_factor_Q16, gainMult_Q8 );
+                    gainMult_Q8 = silk_max_32( 64, gainMult_Q8*4/5 );
                 }
-
             } else {
                 /* Adjust gain by interpolating */
                 gainMult_Q8 = gainMult_lower + silk_DIV32_16( silk_MUL( gainMult_upper - gainMult_lower, maxBits - nBits_lower ), nBits_upper - nBits_lower );
--- a/silk/float/encode_frame_FLP.c
+++ b/silk/float/encode_frame_FLP.c
@@ -306,15 +306,9 @@
             if( ( found_lower & found_upper ) == 0 ) {
                 /* Adjust gain according to high-rate rate/distortion curve */
                 if( nBits > maxBits ) {
-                    if (gainMult_Q8 < 16384) {
-                        gainMult_Q8 *= 2;
-                    } else {
-                        gainMult_Q8 = 32767;
-                    }
+                    gainMult_Q8 = silk_min_32( 1024, gainMult_Q8*3/2 );
                 } else {
-                    opus_int32 gain_factor_Q16;
-                    gain_factor_Q16 = silk_log2lin( silk_LSHIFT( nBits - maxBits, 7 ) / psEnc->sCmn.frame_length + SILK_FIX_CONST( 16, 7 ) );
-                    gainMult_Q8 = silk_SMULWB( gain_factor_Q16, gainMult_Q8 );
+                    gainMult_Q8 = silk_max_32( 64, gainMult_Q8*4/5 );
                 }
             } else {
                 /* Adjust gain by interpolating */
-- 
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