1 | /* -*- mode: C; tab-width:8; c-basic-offset:8 -*- |
---|
2 | * vi:set ts=8: |
---|
3 | * |
---|
4 | * ac_helper.c |
---|
5 | * |
---|
6 | * audioconvert helper funcs. |
---|
7 | * |
---|
8 | * This file and the funcs within taken almost whole from: |
---|
9 | * SDL - Simple DirectMedia Layer |
---|
10 | * Copyright (C) 1997, 1998, 1999 Sam Lantinga |
---|
11 | */ |
---|
12 | |
---|
13 | /* Functions for audio drivers to perform runtime conversion of audio format */ |
---|
14 | |
---|
15 | #include "al_siteconfig.h" |
---|
16 | |
---|
17 | #include <AL/al.h> |
---|
18 | #include <assert.h> |
---|
19 | #include <stdio.h> |
---|
20 | #include <stdlib.h> |
---|
21 | |
---|
22 | #include "audioconvert/audioconvert.h" |
---|
23 | |
---|
24 | void acConvertSign(acAudioCVT *cvt, ALushort format); |
---|
25 | void acConvertEndian(acAudioCVT *cvt, ALushort format); |
---|
26 | |
---|
27 | /* Toggle signed/unsigned */ |
---|
28 | void acConvertSign(acAudioCVT *cvt, ALushort format) { |
---|
29 | int i; |
---|
30 | ALubyte *data; |
---|
31 | |
---|
32 | data = cvt->buf; |
---|
33 | if((format & 0xFF) == 16) { |
---|
34 | if((format & 0x1000) != 0x1000) { /* Little endian */ |
---|
35 | ++data; |
---|
36 | } |
---|
37 | |
---|
38 | for(i = cvt->len_cvt/2; i; i-- ) { |
---|
39 | *data ^= 0x80; |
---|
40 | data += 2; |
---|
41 | } |
---|
42 | } else { |
---|
43 | for(i = cvt->len_cvt; i; i-- ) { |
---|
44 | *data++ ^= 0x80; |
---|
45 | } |
---|
46 | } |
---|
47 | |
---|
48 | format = (format ^ 0x8000); |
---|
49 | |
---|
50 | if (cvt->filters[++cvt->filter_index] ) { |
---|
51 | cvt->filters[cvt->filter_index](cvt, format); |
---|
52 | } |
---|
53 | } |
---|
54 | |
---|
55 | /* Toggle endianness */ |
---|
56 | void acConvertEndian(acAudioCVT *cvt, ALushort format) { |
---|
57 | int i; |
---|
58 | ALubyte *data, tmp; |
---|
59 | |
---|
60 | data = cvt->buf; |
---|
61 | for(i = cvt->len_cvt/2; i; i--) { |
---|
62 | tmp = data[0]; |
---|
63 | data[0] = data[1]; |
---|
64 | data[1] = tmp; |
---|
65 | data += 2; |
---|
66 | } |
---|
67 | |
---|
68 | format = (format ^ 0x1000); |
---|
69 | |
---|
70 | if (cvt->filters[++cvt->filter_index] ) { |
---|
71 | cvt->filters[cvt->filter_index](cvt, format); |
---|
72 | } |
---|
73 | } |
---|
74 | |
---|
75 | |
---|
76 | /* Creates a set of audio filters to convert from one format to another. |
---|
77 | Returns -1 if the format conversion is not supported, or 1 if the |
---|
78 | audio filter is set up. |
---|
79 | */ |
---|
80 | |
---|
81 | int acBuildAudioCVT(acAudioCVT *cvt, |
---|
82 | ALushort src_format, ALubyte src_channels, ALuint src_rate, |
---|
83 | ALushort dst_format, ALubyte dst_channels, ALuint dst_rate) { |
---|
84 | |
---|
85 | /* Start off with no conversion necessary */ |
---|
86 | cvt->needed = 0; |
---|
87 | cvt->filter_index = 0; |
---|
88 | cvt->filters[0] = NULL; |
---|
89 | cvt->len_mult = 1; |
---|
90 | cvt->len_ratio = 1.0; |
---|
91 | |
---|
92 | /* First filter: Endian conversion from src to dst */ |
---|
93 | if((( src_format & 0x1000) != (dst_format & 0x1000)) && |
---|
94 | (( src_format & 0xff) != 8)) |
---|
95 | { |
---|
96 | cvt->filters[cvt->filter_index++] = acConvertEndian; |
---|
97 | } |
---|
98 | |
---|
99 | /* Third filter: Sign conversion -- signed/unsigned */ |
---|
100 | if((src_format & 0x8000) != (dst_format & 0x8000)) { |
---|
101 | cvt->filters[cvt->filter_index++] = acConvertSign; |
---|
102 | } |
---|
103 | |
---|
104 | /* Second filter: Convert 16 bit <--> 8 bit PCM */ |
---|
105 | if((src_format & 0xFF) != (dst_format & 0xFF)) { |
---|
106 | switch(dst_format & 0x10FF) { |
---|
107 | case AUDIO_U8: |
---|
108 | cvt->filters[cvt->filter_index++] = |
---|
109 | acConvert8; |
---|
110 | cvt->len_ratio /= 2; |
---|
111 | break; |
---|
112 | case AUDIO_U16LSB: |
---|
113 | cvt->filters[cvt->filter_index++] = |
---|
114 | acConvert16LSB; |
---|
115 | cvt->len_mult *= 2; |
---|
116 | cvt->len_ratio *= 2; |
---|
117 | break; |
---|
118 | case AUDIO_U16MSB: |
---|
119 | cvt->filters[cvt->filter_index++] = |
---|
120 | acConvert16MSB; |
---|
121 | cvt->len_mult *= 2; |
---|
122 | cvt->len_ratio *= 2; |
---|
123 | break; |
---|
124 | default: |
---|
125 | break; |
---|
126 | } |
---|
127 | } |
---|
128 | |
---|
129 | /* Last filter: Mono/Stereo conversion */ |
---|
130 | if(src_channels != dst_channels) { |
---|
131 | while((src_channels * 2) <= dst_channels) { |
---|
132 | cvt->filters[cvt->filter_index++] = |
---|
133 | acConvertStereo; |
---|
134 | src_channels *= 2; |
---|
135 | cvt->len_mult *= 2; |
---|
136 | cvt->len_ratio *= 2; |
---|
137 | } |
---|
138 | |
---|
139 | /* |
---|
140 | * This assumes that 4 channel audio is in the format: |
---|
141 | * Left {front/back} + Right {front/back} |
---|
142 | * so converting to L/R stereo works properly. |
---|
143 | */ |
---|
144 | while(((src_channels%2) == 0) && |
---|
145 | ((src_channels/2) >= dst_channels)) { |
---|
146 | cvt->filters[cvt->filter_index++] = |
---|
147 | acConvertMono; |
---|
148 | src_channels /= 2; |
---|
149 | cvt->len_ratio /= 2; |
---|
150 | } |
---|
151 | if ( src_channels != dst_channels ) { |
---|
152 | /* Uh oh.. */; |
---|
153 | } |
---|
154 | } |
---|
155 | |
---|
156 | /* Do rate conversion */ |
---|
157 | cvt->rate_incr = 0.0; |
---|
158 | if((src_rate / 100) != (dst_rate / 100)) { |
---|
159 | ALuint hi_rate, lo_rate; |
---|
160 | int len_mult; |
---|
161 | double len_ratio; |
---|
162 | void (*rate_cvt)(acAudioCVT *, ALushort ); |
---|
163 | |
---|
164 | assert(src_rate != 0); |
---|
165 | |
---|
166 | if ( src_rate > dst_rate ) { |
---|
167 | hi_rate = src_rate; |
---|
168 | lo_rate = dst_rate; |
---|
169 | rate_cvt = acFreqDIV2; |
---|
170 | len_mult = 1; |
---|
171 | len_ratio = 0.5; |
---|
172 | } else { |
---|
173 | hi_rate = dst_rate; |
---|
174 | lo_rate = src_rate; |
---|
175 | rate_cvt = acFreqMUL2; |
---|
176 | len_mult = 2; |
---|
177 | len_ratio = 2.0; |
---|
178 | } |
---|
179 | /* If hi_rate = lo_rate*2^x then conversion is easy */ |
---|
180 | while(((lo_rate * 2)/100) <= (hi_rate/100)) { |
---|
181 | cvt->filters[cvt->filter_index++] = rate_cvt; |
---|
182 | lo_rate *= 2; |
---|
183 | cvt->len_mult *= len_mult; |
---|
184 | cvt->len_ratio *= len_ratio; |
---|
185 | } |
---|
186 | |
---|
187 | /* We may need a slow conversion here to finish up */ |
---|
188 | if((lo_rate/100) != (hi_rate/100)) { |
---|
189 | #if 0 |
---|
190 | /* The problem with this is that if the input buffer is |
---|
191 | say 1K, and the conversion rate is say 1.1, then the |
---|
192 | output buffer is 1.1K, which may not be an acceptable |
---|
193 | buffer size for the audio driver (not a power of 2) |
---|
194 | */ |
---|
195 | /* For now, punt and hope the rate distortion isn't great. |
---|
196 | */ |
---|
197 | #else |
---|
198 | if ( src_rate < dst_rate ) { |
---|
199 | cvt->rate_incr = (double)lo_rate/hi_rate; |
---|
200 | cvt->len_mult *= 2; |
---|
201 | cvt->len_ratio /= cvt->rate_incr; |
---|
202 | } else { |
---|
203 | cvt->rate_incr = (double)hi_rate/lo_rate; |
---|
204 | cvt->len_ratio *= cvt->rate_incr; |
---|
205 | } |
---|
206 | cvt->filters[cvt->filter_index++] = acFreqSLOW; |
---|
207 | #endif |
---|
208 | } |
---|
209 | } |
---|
210 | |
---|
211 | /* Set up the filter information */ |
---|
212 | if(cvt->filter_index != 0) { |
---|
213 | cvt->needed = 1; |
---|
214 | cvt->len = 0; |
---|
215 | cvt->buf = NULL; |
---|
216 | cvt->src_format = src_format; |
---|
217 | cvt->dst_format = dst_format; |
---|
218 | cvt->filters[cvt->filter_index] = NULL; |
---|
219 | } |
---|
220 | |
---|
221 | return cvt->needed; |
---|
222 | } |
---|
223 | |
---|
224 | int acConvertAudio(acAudioCVT *cvt) { |
---|
225 | /* Make sure there's data to convert */ |
---|
226 | if(cvt->buf == NULL) { |
---|
227 | #ifdef DEBUG_MAXIMUS |
---|
228 | fprintf(stderr, |
---|
229 | "ALD_MAXIMUS\t[%s:%d]\t %s\n", |
---|
230 | __FILE__, __LINE__, |
---|
231 | "No buffer allocated for conversion"); |
---|
232 | #endif |
---|
233 | return -1; |
---|
234 | } |
---|
235 | |
---|
236 | /* Return okay if no conversion is necessary */ |
---|
237 | cvt->len_cvt = cvt->len; |
---|
238 | if(cvt->filters[0] == NULL) { |
---|
239 | return 0; |
---|
240 | } |
---|
241 | |
---|
242 | /* Set up the conversion and go! */ |
---|
243 | cvt->filter_index = 0; |
---|
244 | cvt->filters[0](cvt, cvt->src_format); |
---|
245 | |
---|
246 | return 0; |
---|
247 | } |
---|