1f6c3c53b305984bab80c415196be5ac184d1bd4
[libav.git] / libavcodec / ac3dec.c
1 /*
2 * AC3 decoder
3 * Copyright (c) 2001 Fabrice Bellard.
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 */
19
20 /**
21 * @file ac3dec.c
22 * AC3 decoder.
23 */
24
25 //#define DEBUG
26
27 #include "avcodec.h"
28 #include "libac3/ac3.h"
29
30 /* currently, I use libac3 which is Copyright (C) Aaron Holtzman and
31 released under the GPL license. I may reimplement it someday... */
32 typedef struct AC3DecodeState {
33 uint8_t inbuf[4096]; /* input buffer */
34 uint8_t *inbuf_ptr;
35 int frame_size;
36 int flags;
37 int channels;
38 ac3_state_t state;
39 } AC3DecodeState;
40
41 static int ac3_decode_init(AVCodecContext *avctx)
42 {
43 AC3DecodeState *s = avctx->priv_data;
44
45 ac3_init ();
46 s->inbuf_ptr = s->inbuf;
47 s->frame_size = 0;
48 return 0;
49 }
50
51 stream_samples_t samples;
52
53 /**** the following two functions comes from ac3dec */
54 static inline int blah (int32_t i)
55 {
56 if (i > 0x43c07fff)
57 return 32767;
58 else if (i < 0x43bf8000)
59 return -32768;
60 else
61 return i - 0x43c00000;
62 }
63
64 static inline void float_to_int (float * _f, int16_t * s16, int nchannels)
65 {
66 int i, j, c;
67 int32_t * f = (int32_t *) _f; // XXX assumes IEEE float format
68
69 j = 0;
70 nchannels *= 256;
71 for (i = 0; i < 256; i++) {
72 for (c = 0; c < nchannels; c += 256)
73 s16[j++] = blah (f[i + c]);
74 }
75 }
76
77 /**** end */
78
79 #define HEADER_SIZE 7
80
81 static int ac3_decode_frame(AVCodecContext *avctx,
82 void *data, int *data_size,
83 uint8_t *buf, int buf_size)
84 {
85 AC3DecodeState *s = avctx->priv_data;
86 uint8_t *buf_ptr;
87 int flags, i, len;
88 int sample_rate, bit_rate;
89 short *out_samples = data;
90 float level;
91 static const int ac3_channels[8] = {
92 2, 1, 2, 3, 3, 4, 4, 5
93 };
94
95 buf_ptr = buf;
96 while (buf_size > 0) {
97 len = s->inbuf_ptr - s->inbuf;
98 if (s->frame_size == 0) {
99 /* no header seen : find one. We need at least 7 bytes to parse it */
100 len = HEADER_SIZE - len;
101 if (len > buf_size)
102 len = buf_size;
103 memcpy(s->inbuf_ptr, buf_ptr, len);
104 buf_ptr += len;
105 s->inbuf_ptr += len;
106 buf_size -= len;
107 if ((s->inbuf_ptr - s->inbuf) == HEADER_SIZE) {
108 len = ac3_syncinfo (s->inbuf, &s->flags, &sample_rate, &bit_rate);
109 if (len == 0) {
110 /* no sync found : move by one byte (inefficient, but simple!) */
111 memcpy(s->inbuf, s->inbuf + 1, HEADER_SIZE - 1);
112 s->inbuf_ptr--;
113 } else {
114 s->frame_size = len;
115 /* update codec info */
116 avctx->sample_rate = sample_rate;
117 s->channels = ac3_channels[s->flags & 7];
118 if (s->flags & AC3_LFE)
119 s->channels++;
120 if (avctx->channels == 0)
121 /* No specific number of channel requested */
122 avctx->channels = s->channels;
123 else if (s->channels < avctx->channels) {
124 av_log( avctx, AV_LOG_INFO, "ac3dec: AC3 Source channels are less than specified: output to %d channels.. (frmsize: %d)\n", s->channels, len);
125 avctx->channels = s->channels;
126 }
127 avctx->bit_rate = bit_rate;
128 }
129 }
130 } else if (len < s->frame_size) {
131 len = s->frame_size - len;
132 if (len > buf_size)
133 len = buf_size;
134
135 memcpy(s->inbuf_ptr, buf_ptr, len);
136 buf_ptr += len;
137 s->inbuf_ptr += len;
138 buf_size -= len;
139 } else {
140 flags = s->flags;
141 if (avctx->channels == 1)
142 flags = AC3_MONO;
143 else if (avctx->channels == 2)
144 flags = AC3_STEREO;
145 else
146 flags |= AC3_ADJUST_LEVEL;
147 level = 1;
148 if (ac3_frame (&s->state, s->inbuf, &flags, &level, 384)) {
149 fail:
150 s->inbuf_ptr = s->inbuf;
151 s->frame_size = 0;
152 continue;
153 }
154 for (i = 0; i < 6; i++) {
155 if (ac3_block (&s->state))
156 goto fail;
157 float_to_int (*samples, out_samples + i * 256 * avctx->channels, avctx->channels);
158 }
159 s->inbuf_ptr = s->inbuf;
160 s->frame_size = 0;
161 *data_size = 6 * avctx->channels * 256 * sizeof(int16_t);
162 break;
163 }
164 }
165 return buf_ptr - buf;
166 }
167
168 static int ac3_decode_end(AVCodecContext *s)
169 {
170 return 0;
171 }
172
173 AVCodec ac3_decoder = {
174 "ac3",
175 CODEC_TYPE_AUDIO,
176 CODEC_ID_AC3,
177 sizeof(AC3DecodeState),
178 ac3_decode_init,
179 NULL,
180 ac3_decode_end,
181 ac3_decode_frame,
182 };