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4 modification, are permitted provided that the following conditions
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15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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26 ***********************************************************************/
27
28 #ifdef HAVE_CONFIG_H
29 #include "config.h"
30 #endif
31
32 #include "SigProc_FIX.h"
33 #include "resampler_private.h"
34 #include "stack_alloc.h"
35
36 #define ORDER_FIR 4
37
38 /* Downsample by a factor 2/3, low quality */
silk_resampler_down2_3(opus_int32 * S,opus_int16 * out,const opus_int16 * in,opus_int32 inLen)39 void silk_resampler_down2_3(
40 opus_int32 *S, /* I/O State vector [ 6 ] */
41 opus_int16 *out, /* O Output signal [ floor(2*inLen/3) ] */
42 const opus_int16 *in, /* I Input signal [ inLen ] */
43 opus_int32 inLen /* I Number of input samples */
44 )
45 {
46 opus_int32 nSamplesIn, counter, res_Q6;
47 VARDECL( opus_int32, buf );
48 opus_int32 *buf_ptr;
49 SAVE_STACK;
50
51 ALLOC( buf, RESAMPLER_MAX_BATCH_SIZE_IN + ORDER_FIR, opus_int32 );
52
53 /* Copy buffered samples to start of buffer */
54 silk_memcpy( buf, S, ORDER_FIR * sizeof( opus_int32 ) );
55
56 /* Iterate over blocks of frameSizeIn input samples */
57 while( 1 ) {
58 nSamplesIn = silk_min( inLen, RESAMPLER_MAX_BATCH_SIZE_IN );
59
60 /* Second-order AR filter (output in Q8) */
61 silk_resampler_private_AR2( &S[ ORDER_FIR ], &buf[ ORDER_FIR ], in,
62 silk_Resampler_2_3_COEFS_LQ, nSamplesIn );
63
64 /* Interpolate filtered signal */
65 buf_ptr = buf;
66 counter = nSamplesIn;
67 while( counter > 2 ) {
68 /* Inner product */
69 res_Q6 = silk_SMULWB( buf_ptr[ 0 ], silk_Resampler_2_3_COEFS_LQ[ 2 ] );
70 res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 1 ], silk_Resampler_2_3_COEFS_LQ[ 3 ] );
71 res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 2 ], silk_Resampler_2_3_COEFS_LQ[ 5 ] );
72 res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 3 ], silk_Resampler_2_3_COEFS_LQ[ 4 ] );
73
74 /* Scale down, saturate and store in output array */
75 *out++ = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( res_Q6, 6 ) );
76
77 res_Q6 = silk_SMULWB( buf_ptr[ 1 ], silk_Resampler_2_3_COEFS_LQ[ 4 ] );
78 res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 2 ], silk_Resampler_2_3_COEFS_LQ[ 5 ] );
79 res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 3 ], silk_Resampler_2_3_COEFS_LQ[ 3 ] );
80 res_Q6 = silk_SMLAWB( res_Q6, buf_ptr[ 4 ], silk_Resampler_2_3_COEFS_LQ[ 2 ] );
81
82 /* Scale down, saturate and store in output array */
83 *out++ = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( res_Q6, 6 ) );
84
85 buf_ptr += 3;
86 counter -= 3;
87 }
88
89 in += nSamplesIn;
90 inLen -= nSamplesIn;
91
92 if( inLen > 0 ) {
93 /* More iterations to do; copy last part of filtered signal to beginning of buffer */
94 silk_memcpy( buf, &buf[ nSamplesIn ], ORDER_FIR * sizeof( opus_int32 ) );
95 } else {
96 break;
97 }
98 }
99
100 /* Copy last part of filtered signal to the state for the next call */
101 silk_memcpy( S, &buf[ nSamplesIn ], ORDER_FIR * sizeof( opus_int32 ) );
102 RESTORE_STACK;
103 }
104