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1 | /* |
2 | * The following ADPCM algorithm was stolen from MAME aica driver. |
3 | * I'm quite sure it's not the right one, but it's the |
4 | * best sounding of the ones that I tried. |
5 | */ |
6 | |
7 | #include "../PicoInt.h" |
8 | |
9 | #define ADPCMSHIFT 8 |
10 | #define ADFIX(f) (int) ((double)f * (double)(1<<ADPCMSHIFT)) |
11 | |
12 | /* limitter */ |
13 | #define Limit(val, max, min) { \ |
14 | if ( val > max ) val = max; \ |
15 | else if ( val < min ) val = min; \ |
16 | } |
17 | |
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18 | static const int TableQuant[8] = |
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19 | { |
20 | ADFIX(0.8984375), |
21 | ADFIX(0.8984375), |
22 | ADFIX(0.8984375), |
23 | ADFIX(0.8984375), |
24 | ADFIX(1.19921875), |
25 | ADFIX(1.59765625), |
26 | ADFIX(2.0), |
27 | ADFIX(2.3984375) |
28 | }; |
29 | |
30 | // changed using trial and error.. |
31 | //const int quant_mul[16] = { 1, 3, 5, 7, 9, 11, 13, 15, -1, -3, -5, -7, -9, -11, -13, -15 }; |
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32 | static const int quant_mul[16] = { 1, 3, 5, 7, 9, 11, 13, -1, -1, -3, -5, -7, -9, -11, -13, -15 }; |
33 | |
34 | static int sample = 0, quant = 0, sgn = 0; |
35 | static int stepsamples = (44100<<10)/16000; |
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36 | |
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37 | |
38 | PICO_INTERNAL void PicoPicoPCMReset(void) |
39 | { |
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40 | sample = sgn = 0; |
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41 | quant = 0x7f; |
42 | memset(PicoPicohw.xpcm_buffer, 0, sizeof(PicoPicohw.xpcm_buffer)); |
43 | } |
44 | |
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45 | PICO_INTERNAL void PicoPicoPCMRerate(void) |
46 | { |
47 | stepsamples = (PsndRate<<10)/16000; |
48 | } |
49 | |
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50 | #define XSHIFT 7 |
51 | |
52 | #define do_sample() \ |
53 | { \ |
54 | sample += quant * quant_mul[srcval] >> XSHIFT; \ |
55 | quant = (quant * TableQuant[srcval&7]) >> ADPCMSHIFT; \ |
56 | Limit(quant, 0x6000, 0x7f); \ |
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57 | Limit(sample, 32767/2, -32768/2); \ |
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58 | } |
59 | |
60 | PICO_INTERNAL void PicoPicoPCMUpdate(short *buffer, int length, int stereo) |
61 | { |
62 | unsigned char *src = PicoPicohw.xpcm_buffer; |
63 | unsigned char *lim = PicoPicohw.xpcm_ptr; |
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64 | int srcval, needsamples = 0; |
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65 | |
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66 | if (src == lim) goto end; |
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67 | |
68 | for (; length > 0 && src < lim; src++) |
69 | { |
70 | srcval = *src >> 4; |
71 | do_sample(); |
72 | |
73 | for (needsamples += stepsamples; needsamples > (1<<10) && length > 0; needsamples -= (1<<10), length--) { |
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74 | *buffer++ += sample; |
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75 | if (stereo) { buffer[0] = buffer[-1]; buffer++; } |
76 | } |
77 | |
78 | srcval = *src & 0xf; |
79 | do_sample(); |
80 | |
81 | for (needsamples += stepsamples; needsamples > (1<<10) && length > 0; needsamples -= (1<<10), length--) { |
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82 | *buffer++ += sample; |
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83 | if (stereo) { buffer[0] = buffer[-1]; buffer++; } |
84 | } |
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85 | |
86 | // lame normalization stuff, needed due to wrong adpcm algo |
87 | sgn += (sample < 0) ? -1 : 1; |
88 | if (sgn < -16 || sgn > 16) sample -= sample >> 5; |
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89 | } |
90 | |
91 | if (src < lim) { |
92 | int di = lim - src; |
93 | memmove(PicoPicohw.xpcm_buffer, src, di); |
94 | PicoPicohw.xpcm_ptr = PicoPicohw.xpcm_buffer + di; |
95 | elprintf(EL_STATUS, "xpcm update: over %i", di); |
ed367a3f |
96 | // adjust fifo |
97 | PicoPicohw.fifo_bytes = di; |
98 | return; |
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99 | } |
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100 | |
101 | elprintf(EL_STATUS, "xpcm update: under %i", length); |
102 | PicoPicohw.xpcm_ptr = PicoPicohw.xpcm_buffer; |
103 | |
104 | end: |
105 | if (stereo) |
106 | // still must expand SN76496 to stereo |
107 | for (; length > 0; buffer+=2, length--) |
108 | buffer[1] = buffer[0]; |
109 | |
110 | sample = sgn = 0; |
111 | quant = 0x7f; |
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112 | } |
113 | |