1/***********************************************************************
2Copyright (c) 2006-2011, Skype Limited. All rights reserved.
3Redistribution and use in source and binary forms, with or without
4modification, are permitted provided that the following conditions
5are met:
6- Redistributions of source code must retain the above copyright notice,
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8- Redistributions in binary form must reproduce the above copyright
9notice, this list of conditions and the following disclaimer in the
10documentation and/or other materials provided with the distribution.
11- Neither the name of Internet Society, IETF or IETF Trust, nor the
12names of specific contributors, may be used to endorse or promote
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14permission.
15THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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18ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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24ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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26***********************************************************************/
27
28#ifdef HAVE_CONFIG_H
29#include "config.h"
30#endif
31
32#include "main.h"
33#include "tuning_parameters.h"
34
35/* Control SNR of redidual quantizer */
36opus_int silk_control_SNR(
37    silk_encoder_state          *psEncC,                        /* I/O  Pointer to Silk encoder state               */
38    opus_int32                  TargetRate_bps                  /* I    Target max bitrate (bps)                    */
39)
40{
41    opus_int k, ret = SILK_NO_ERROR;
42    opus_int32 frac_Q6;
43    const opus_int32 *rateTable;
44
45    /* Set bitrate/coding quality */
46    TargetRate_bps = silk_LIMIT( TargetRate_bps, MIN_TARGET_RATE_BPS, MAX_TARGET_RATE_BPS );
47    if( TargetRate_bps != psEncC->TargetRate_bps ) {
48        psEncC->TargetRate_bps = TargetRate_bps;
49
50        /* If new TargetRate_bps, translate to SNR_dB value */
51        if( psEncC->fs_kHz == 8 ) {
52            rateTable = silk_TargetRate_table_NB;
53        } else if( psEncC->fs_kHz == 12 ) {
54            rateTable = silk_TargetRate_table_MB;
55        } else {
56            rateTable = silk_TargetRate_table_WB;
57        }
58
59        /* Reduce bitrate for 10 ms modes in these calculations */
60        if( psEncC->nb_subfr == 2 ) {
61            TargetRate_bps -= REDUCE_BITRATE_10_MS_BPS;
62        }
63
64        /* Find bitrate interval in table and interpolate */
65        for( k = 1; k < TARGET_RATE_TAB_SZ; k++ ) {
66            if( TargetRate_bps <= rateTable[ k ] ) {
67                frac_Q6 = silk_DIV32( silk_LSHIFT( TargetRate_bps - rateTable[ k - 1 ], 6 ),
68                                                 rateTable[ k ] - rateTable[ k - 1 ] );
69                psEncC->SNR_dB_Q7 = silk_LSHIFT( silk_SNR_table_Q1[ k - 1 ], 6 ) + silk_MUL( frac_Q6, silk_SNR_table_Q1[ k ] - silk_SNR_table_Q1[ k - 1 ] );
70                break;
71            }
72        }
73
74        /* Reduce coding quality whenever LBRR is enabled, to free up some bits */
75        if( psEncC->LBRR_enabled ) {
76            psEncC->SNR_dB_Q7 = silk_SMLABB( psEncC->SNR_dB_Q7, 12 - psEncC->LBRR_GainIncreases, SILK_FIX_CONST( -0.25, 7 ) );
77        }
78    }
79
80    return ret;
81}
82