646442bf03e47d0ca0ddc2255235d13048f3ae21
[libav.git] / libavcodec / mlp_parser.c
1 /*
2 * MLP parser
3 * Copyright (c) 2007 Ian Caulfield
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 /**
23 * @file mlp_parser.c
24 * MLP parser
25 */
26
27 #include <stdint.h>
28
29 #include "libavutil/crc.h"
30 #include "bitstream.h"
31 #include "parser.h"
32 #include "mlp_parser.h"
33
34 static const uint8_t mlp_quants[16] = {
35 16, 20, 24, 0, 0, 0, 0, 0,
36 0, 0, 0, 0, 0, 0, 0, 0,
37 };
38
39 static const uint8_t mlp_channels[32] = {
40 1, 2, 3, 4, 3, 4, 5, 3, 4, 5, 4, 5, 6, 4, 5, 4,
41 5, 6, 5, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
42 };
43
44 static const uint8_t thd_chancount[13] = {
45 // LR C LFE LRs LRvh LRc LRrs Cs Ts LRsd LRw Cvh LFE2
46 2, 1, 1, 2, 2, 2, 2, 1, 1, 2, 2, 1, 1
47 };
48
49 static int mlp_samplerate(int in)
50 {
51 if (in == 0xF)
52 return 0;
53
54 return (in & 8 ? 44100 : 48000) << (in & 7) ;
55 }
56
57 static int truehd_channels(int chanmap)
58 {
59 int channels = 0, i;
60
61 for (i = 0; i < 13; i++)
62 channels += thd_chancount[i] * ((chanmap >> i) & 1);
63
64 return channels;
65 }
66
67 static int crc_init = 0;
68 static AVCRC crc_2D[1024];
69
70 /** MLP uses checksums that seem to be based on the standard CRC algorithm, but
71 * are not (in implementation terms, the table lookup and XOR are reversed).
72 * We can implement this behavior using a standard av_crc on all but the
73 * last element, then XOR that with the last element.
74 */
75
76 static uint16_t mlp_checksum16(const uint8_t *buf, unsigned int buf_size)
77 {
78 uint16_t crc;
79
80 if (!crc_init) {
81 av_crc_init(crc_2D, 0, 16, 0x002D, sizeof(crc_2D));
82 crc_init = 1;
83 }
84
85 crc = av_crc(crc_2D, 0, buf, buf_size - 2);
86 crc ^= AV_RL16(buf + buf_size - 2);
87 return crc;
88 }
89
90 /** Read a major sync info header - contains high level information about
91 * the stream - sample rate, channel arrangement etc. Most of this
92 * information is not actually necessary for decoding, only for playback.
93 * gb must be a freshly initialized GetBitContext with no bits read.
94 */
95
96 int ff_mlp_read_major_sync(void *log, MLPHeaderInfo *mh, GetBitContext *gb)
97 {
98 int ratebits;
99 uint16_t checksum;
100
101 assert(get_bits_count(gb) == 0);
102
103 if (gb->size_in_bits < 28 << 3) {
104 av_log(log, AV_LOG_ERROR, "packet too short, unable to read major sync\n");
105 return -1;
106 }
107
108 checksum = mlp_checksum16(gb->buffer, 26);
109 if (checksum != AV_RL16(gb->buffer+26)) {
110 av_log(log, AV_LOG_ERROR, "major sync info header checksum error\n");
111 return -1;
112 }
113
114 if (get_bits_long(gb, 24) != 0xf8726f) /* Sync words */
115 return -1;
116
117 mh->stream_type = get_bits(gb, 8);
118
119 if (mh->stream_type == 0xbb) {
120 mh->group1_bits = mlp_quants[get_bits(gb, 4)];
121 mh->group2_bits = mlp_quants[get_bits(gb, 4)];
122
123 ratebits = get_bits(gb, 4);
124 mh->group1_samplerate = mlp_samplerate(ratebits);
125 mh->group2_samplerate = mlp_samplerate(get_bits(gb, 4));
126
127 skip_bits(gb, 11);
128
129 mh->channels_mlp = get_bits(gb, 5);
130 } else if (mh->stream_type == 0xba) {
131 mh->group1_bits = 24; // TODO: Is this information actually conveyed anywhere?
132 mh->group2_bits = 0;
133
134 ratebits = get_bits(gb, 4);
135 mh->group1_samplerate = mlp_samplerate(ratebits);
136 mh->group2_samplerate = 0;
137
138 skip_bits(gb, 8);
139
140 mh->channels_thd_stream1 = get_bits(gb, 5);
141
142 skip_bits(gb, 2);
143
144 mh->channels_thd_stream2 = get_bits(gb, 13);
145 } else
146 return -1;
147
148 mh->access_unit_size = 40 << (ratebits & 7);
149 mh->access_unit_size_pow2 = 64 << (ratebits & 7);
150
151 skip_bits_long(gb, 48);
152
153 mh->is_vbr = get_bits1(gb);
154
155 mh->peak_bitrate = (get_bits(gb, 15) * mh->group1_samplerate + 8) >> 4;
156
157 mh->num_substreams = get_bits(gb, 4);
158
159 skip_bits_long(gb, 4 + 11 * 8);
160
161 return 0;
162 }
163
164 typedef struct MLPParseContext
165 {
166 ParseContext pc;
167
168 int bytes_left;
169
170 int in_sync;
171
172 int num_substreams;
173 } MLPParseContext;
174
175 static int mlp_parse(AVCodecParserContext *s,
176 AVCodecContext *avctx,
177 const uint8_t **poutbuf, int *poutbuf_size,
178 const uint8_t *buf, int buf_size)
179 {
180 MLPParseContext *mp = s->priv_data;
181 int sync_present;
182 uint8_t parity_bits;
183 int next;
184 int i, p = 0;
185
186 *poutbuf_size = 0;
187 if (buf_size == 0)
188 return 0;
189
190 if (!mp->in_sync) {
191 // Not in sync - find a major sync header
192
193 for (i = 0; i < buf_size; i++) {
194 mp->pc.state = (mp->pc.state << 8) | buf[i];
195 if ((mp->pc.state & 0xfffffffe) == 0xf8726fba) {
196 mp->in_sync = 1;
197 mp->bytes_left = 0;
198 break;
199 }
200 }
201
202 if (!mp->in_sync) {
203 ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
204 return buf_size;
205 }
206
207 ff_combine_frame(&mp->pc, i - 7, &buf, &buf_size);
208
209 return i - 7;
210 }
211
212 if (mp->bytes_left == 0) {
213 // Find length of this packet
214
215 /* Copy overread bytes from last frame into buffer. */
216 for(; mp->pc.overread>0; mp->pc.overread--) {
217 mp->pc.buffer[mp->pc.index++]= mp->pc.buffer[mp->pc.overread_index++];
218 }
219
220 if (mp->pc.index + buf_size < 2) {
221 ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
222 return buf_size;
223 }
224
225 mp->bytes_left = ((mp->pc.index > 0 ? mp->pc.buffer[0] : buf[0]) << 8)
226 | (mp->pc.index > 1 ? mp->pc.buffer[1] : buf[1-mp->pc.index]);
227 mp->bytes_left = (mp->bytes_left & 0xfff) * 2;
228 mp->bytes_left -= mp->pc.index;
229 }
230
231 next = (mp->bytes_left > buf_size) ? END_NOT_FOUND : mp->bytes_left;
232
233 if (ff_combine_frame(&mp->pc, next, &buf, &buf_size) < 0) {
234 mp->bytes_left -= buf_size;
235 return buf_size;
236 }
237
238 mp->bytes_left = 0;
239
240 sync_present = (AV_RB32(buf + 4) & 0xfffffffe) == 0xf8726fba;
241
242 if (!sync_present) {
243 /* The first nibble of a frame is a parity check of the 4-byte
244 * access unit header and all the 2- or 4-byte substream headers. */
245 // Only check when this isn't a sync frame - syncs have a checksum.
246
247 parity_bits = 0;
248 for (i = -1; i < mp->num_substreams; i++) {
249 parity_bits ^= buf[p++];
250 parity_bits ^= buf[p++];
251
252 if (i < 0 || buf[p-2] & 0x80) {
253 parity_bits ^= buf[p++];
254 parity_bits ^= buf[p++];
255 }
256 }
257
258 if ((((parity_bits >> 4) ^ parity_bits) & 0xF) != 0xF) {
259 av_log(avctx, AV_LOG_INFO, "mlpparse: Parity check failed.\n");
260 goto lost_sync;
261 }
262 } else {
263 GetBitContext gb;
264 MLPHeaderInfo mh;
265
266 init_get_bits(&gb, buf + 4, (buf_size - 4) << 3);
267 if (ff_mlp_read_major_sync(avctx, &mh, &gb) < 0)
268 goto lost_sync;
269
270 #ifdef CONFIG_AUDIO_NONSHORT
271 avctx->bits_per_sample = mh.group1_bits;
272 if (avctx->bits_per_sample > 16)
273 avctx->sample_fmt = SAMPLE_FMT_S32;
274 #endif
275 avctx->sample_rate = mh.group1_samplerate;
276 avctx->frame_size = mh.access_unit_size;
277
278 if (mh.stream_type == 0xbb) {
279 /* MLP stream */
280 avctx->channels = mlp_channels[mh.channels_mlp];
281 } else { /* mh.stream_type == 0xba */
282 /* TrueHD stream */
283 if (mh.channels_thd_stream2)
284 avctx->channels = truehd_channels(mh.channels_thd_stream2);
285 else
286 avctx->channels = truehd_channels(mh.channels_thd_stream1);
287 }
288
289 if (!mh.is_vbr) /* Stream is CBR */
290 avctx->bit_rate = mh.peak_bitrate;
291
292 mp->num_substreams = mh.num_substreams;
293 }
294
295 *poutbuf = buf;
296 *poutbuf_size = buf_size;
297
298 return next;
299
300 lost_sync:
301 mp->in_sync = 0;
302 return 1;
303 }
304
305 AVCodecParser mlp_parser = {
306 { CODEC_ID_MLP },
307 sizeof(MLPParseContext),
308 NULL,
309 mlp_parse,
310 NULL,
311 };