shithub: opus

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ref: fe84c3bceeb9536725d5500cb984c165f52b8b25
parent: eb1759736f03bb171907b5d31da9ca135f7c21e5
author: Jean-Marc Valin <jmvalin@amazon.com>
date: Sun Jul 9 09:05:08 EDT 2023 

Make "VBR with cap" less aggressive

The bits we don't use won't be wasted, so it's less important to
get exactly the optimal number of bits below the cap.


--- a/silk/fixed/encode_frame_FIX.c
+++ b/silk/fixed/encode_frame_FIX.c
@@ -105,8 +105,11 @@
     opus_int     gain_lock[ MAX_NB_SUBFR ] = {0};
     opus_int16   best_gain_mult[ MAX_NB_SUBFR ];
     opus_int     best_sum[ MAX_NB_SUBFR ];
+    opus_int     bits_margin;
     SAVE_STACK;
 
+    /* For CBR, 5 bits below budget is close enough. For VBR, allow up to 25% below the cap if we initially busted the budget. */
+    bits_margin = useCBR ? 5 : maxBits/4;
     /* This is totally unnecessary but many compilers (including gcc) are too dumb to realise it */
     LastGainIndex_copy2 = nBits_lower = nBits_upper = gainMult_lower = gainMult_upper = 0;
 
@@ -282,7 +285,7 @@
                     gainMult_upper = gainMult_Q8;
                     gainsID_upper = gainsID;
                 }
-            } else if( nBits < maxBits - 5 ) {
+            } else if( nBits < maxBits - bits_margin ) {
                 found_lower = 1;
                 nBits_lower = nBits;
                 gainMult_lower = gainMult_Q8;
@@ -296,7 +299,7 @@
                     LastGainIndex_copy2 = psEnc->sShape.LastGainIndex;
                 }
             } else {
-                /* Within 5 bits of budget: close enough */
+                /* Close enough */
                 break;
             }
 
--- a/silk/float/encode_frame_FLP.c
+++ b/silk/float/encode_frame_FLP.c
@@ -107,7 +107,10 @@
     opus_int     gain_lock[ MAX_NB_SUBFR ] = {0};
     opus_int16   best_gain_mult[ MAX_NB_SUBFR ];
     opus_int     best_sum[ MAX_NB_SUBFR ];
+    opus_int     bits_margin;
 
+    /* For CBR, 5 bits below budget is close enough. For VBR, allow up to 25% below the cap if we initially busted the budget. */
+    bits_margin = useCBR ? 5 : maxBits/4;
     /* This is totally unnecessary but many compilers (including gcc) are too dumb to realise it */
     LastGainIndex_copy2 = nBits_lower = nBits_upper = gainMult_lower = gainMult_upper = 0;
 
@@ -270,7 +273,7 @@
                     gainMult_upper = gainMult_Q8;
                     gainsID_upper = gainsID;
                 }
-            } else if( nBits < maxBits - 5 ) {
+            } else if( nBits < maxBits - bits_margin ) {
                 found_lower = 1;
                 nBits_lower = nBits;
                 gainMult_lower = gainMult_Q8;
@@ -284,7 +287,7 @@
                     LastGainIndex_copy2 = psEnc->sShape.LastGainIndex;
                 }
             } else {
-                /* Within 5 bits of budget: close enough */
+                /* Close enough */
                 break;
             }
 
-- 
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