shithub: opus

Info  •  Files  •  Log  •  Branches

Using 64-bit acculumation for C0 in silk_burg_modified()

Signed-off-by: Jean-Marc Valin <[email protected]>

--- a/silk/fixed/burg_modified_FIX.c

+++ b/silk/fixed/burg_modified_FIX.c

@@ -54,7 +54,7 @@

     int                         arch                /* I    Run-time architecture                                       */

 )

 {

-    opus_int         k, n, s, lz, rshifts, rshifts_extra, reached_max_gain;

+    opus_int         k, n, s, lz, rshifts, reached_max_gain;

     opus_int32       C0, num, nrg, rc_Q31, invGain_Q30, Atmp_QA, Atmp1, tmp1, tmp2, x1, x2;

     const opus_int16 *x_ptr;

     opus_int32       C_first_row[ SILK_MAX_ORDER_LPC ];

@@ -63,27 +63,23 @@

     opus_int32       CAf[ SILK_MAX_ORDER_LPC + 1 ];

     opus_int32       CAb[ SILK_MAX_ORDER_LPC + 1 ];

     opus_int32       xcorr[ SILK_MAX_ORDER_LPC ];

+    opus_int64       C0_64;

     silk_assert( subfr_length * nb_subfr <= MAX_FRAME_SIZE );

     /* Compute autocorrelations, added over subframes */

-    silk_sum_sqr_shift( &C0, &rshifts, x, nb_subfr * subfr_length );

-    if( rshifts > MAX_RSHIFTS ) {

-        C0 = silk_LSHIFT32( C0, rshifts - MAX_RSHIFTS );

-        silk_assert( C0 > 0 );

-        rshifts = MAX_RSHIFTS;

+    C0_64 = silk_inner_prod16_aligned_64( x, x, subfr_length*nb_subfr );

+    lz = silk_CLZ64(C0_64);

+    rshifts = 32 + 1 + N_BITS_HEAD_ROOM - lz;

+    if (rshifts > MAX_RSHIFTS) rshifts = MAX_RSHIFTS;

+    if (rshifts < MIN_RSHIFTS) rshifts = MIN_RSHIFTS;

+    

+    if (rshifts > 0) {

+        C0 = (opus_int32)silk_RSHIFT64(C0_64, rshifts );        

     } else {

-        lz = silk_CLZ32( C0 ) - 1;

-        rshifts_extra = N_BITS_HEAD_ROOM - lz;

-        if( rshifts_extra > 0 ) {

-            rshifts_extra = silk_min( rshifts_extra, MAX_RSHIFTS - rshifts );

-            C0 = silk_RSHIFT32( C0, rshifts_extra );

-        } else {

-            rshifts_extra = silk_max( rshifts_extra, MIN_RSHIFTS - rshifts );

-            C0 = silk_LSHIFT32( C0, -rshifts_extra );

-        }

-        rshifts += rshifts_extra;

+        C0 = silk_LSHIFT32((opus_int32)C0_64, -rshifts );

     }

+    

     CAb[ 0 ] = CAf[ 0 ] = C0 + silk_SMMUL( SILK_FIX_CONST( FIND_LPC_COND_FAC, 32 ), C0 ) + 1;                                /* Q(-rshifts) */

     silk_memset( C_first_row, 0, SILK_MAX_ORDER_LPC * sizeof( opus_int32 ) );

     if( rshifts > 0 ) {