Make ff_mlp_read_major_sync() take a GetBitContext instead of buffers.
[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 "libavutil/crc.h"
28 #include "bitstream.h"
29 #include "parser.h"
30 #include "mlp_parser.h"
31
32 static const uint8_t mlp_quants[16] = {
33 16, 20, 24, 0, 0, 0, 0, 0,
34 0, 0, 0, 0, 0, 0, 0, 0,
35 };
36
37 static const uint8_t mlp_channels[32] = {
38 1, 2, 3, 4, 3, 4, 5, 3, 4, 5, 4, 5, 6, 4, 5, 4,
39 5, 6, 5, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
40 };
41
42 static const uint8_t thd_chancount[13] = {
43 // LR C LFE LRs LRvh LRc LRrs Cs Ts LRsd LRw Cvh LFE2
44 2, 1, 1, 2, 2, 2, 2, 1, 1, 2, 2, 1, 1
45 };
46
47 static int mlp_samplerate(int in)
48 {
49 if (in == 0xF)
50 return 0;
51
52 return (in & 8 ? 44100 : 48000) << (in & 7) ;
53 }
54
55 static int truehd_channels(int chanmap)
56 {
57 int channels = 0, i;
58
59 for (i = 0; i < 13; i++)
60 channels += thd_chancount[i] * ((chanmap >> i) & 1);
61
62 return channels;
63 }
64
65 static int crc_init = 0;
66 static AVCRC crc_2D[1024];
67
68 /** MLP uses checksums that seem to be based on the standard CRC algorithm,
69 * but not (in implementation terms, the table lookup and XOR are reversed).
70 * We can implement this behavior using a standard av_crc on all but the
71 * last element, then XOR that with the last element.
72 */
73
74 static uint16_t mlp_checksum16(const uint8_t *buf, unsigned int buf_size)
75 {
76 uint16_t crc;
77
78 if (!crc_init) {
79 av_crc_init(crc_2D, 0, 16, 0x002D, sizeof(crc_2D));
80 crc_init = 1;
81 }
82
83 crc = av_crc(crc_2D, 0, buf, buf_size - 2);
84 crc ^= AV_RL16(buf + buf_size - 2);
85 return crc;
86 }
87
88 /** Read a major sync info header - contains high level information about
89 * the stream - sample rate, channel arrangement etc. Most of this
90 * information is not actually necessary for decoding, only for playback.
91 * gb must be a freshly initialized GetBitContext with no bits read.
92 */
93
94 int ff_mlp_read_major_sync(void *log, MLPHeaderInfo *mh, GetBitContext *gb)
95 {
96 int ratebits;
97 uint16_t checksum;
98
99 assert(get_bits_count(gb) == 0);
100
101 if (gb->size_in_bits < 28 << 3) {
102 av_log(log, AV_LOG_ERROR, "Packet too short, unable to read major sync\n");
103 return -1;
104 }
105
106 checksum = mlp_checksum16(gb->buffer, 26);
107 if (checksum != AV_RL16(gb->buffer+26)) {
108 av_log(log, AV_LOG_ERROR, "Major sync info header checksum error\n");
109 return -1;
110 }
111
112 if (get_bits_long(gb, 24) != 0xf8726f) /* Sync words */
113 return -1;
114
115 mh->stream_type = get_bits(gb, 8);
116
117 if (mh->stream_type == 0xbb) {
118 mh->group1_bits = mlp_quants[get_bits(gb, 4)];
119 mh->group2_bits = mlp_quants[get_bits(gb, 4)];
120
121 ratebits = get_bits(gb, 4);
122 mh->group1_samplerate = mlp_samplerate(ratebits);
123 mh->group2_samplerate = mlp_samplerate(get_bits(gb, 4));
124
125 skip_bits(gb, 11);
126
127 mh->channels_mlp = get_bits(gb, 5);
128 } else if (mh->stream_type == 0xba) {
129 mh->group1_bits = 24; // TODO: Is this information actually conveyed anywhere?
130 mh->group2_bits = 0;
131
132 ratebits = get_bits(gb, 4);
133 mh->group1_samplerate = mlp_samplerate(ratebits);
134 mh->group2_samplerate = 0;
135
136 skip_bits(gb, 8);
137
138 mh->channels_thd_stream1 = get_bits(gb, 5);
139
140 skip_bits(gb, 2);
141
142 mh->channels_thd_stream2 = get_bits(gb, 13);
143 } else
144 return -1;
145
146 mh->access_unit_size = 40 << (ratebits & 7);
147 mh->access_unit_size_pow2 = 64 << (ratebits & 7);
148
149 skip_bits_long(gb, 48);
150
151 mh->is_vbr = get_bits1(gb);
152
153 mh->peak_bitrate = (get_bits(gb, 15) * mh->group1_samplerate + 8) >> 4;
154
155 mh->num_substreams = get_bits(gb, 4);
156
157 skip_bits_long(gb, 4 + 11 * 8);
158
159 return 0;
160 }
161
162 typedef struct MLPParseContext
163 {
164 ParseContext pc;
165
166 int bytes_left;
167
168 int in_sync;
169
170 int num_substreams;
171 } MLPParseContext;
172
173 static int mlp_parse(AVCodecParserContext *s,
174 AVCodecContext *avctx,
175 const uint8_t **poutbuf, int *poutbuf_size,
176 const uint8_t *buf, int buf_size)
177 {
178 MLPParseContext *mp = s->priv_data;
179 int sync_present;
180 uint8_t parity_bits;
181 int next;
182 int i, p = 0;
183
184 *poutbuf_size = 0;
185 if (buf_size == 0)
186 return 0;
187
188 if (!mp->in_sync) {
189 // Not in sync - find a major sync header
190
191 for (i = 0; i < buf_size; i++) {
192 mp->pc.state = (mp->pc.state << 8) | buf[i];
193 if ((mp->pc.state & 0xfffffffe) == 0xf8726fba) {
194 mp->in_sync = 1;
195 mp->bytes_left = 0;
196 break;
197 }
198 }
199
200 if (!mp->in_sync) {
201 ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
202 return buf_size;
203 }
204
205 ff_combine_frame(&mp->pc, i - 7, &buf, &buf_size);
206
207 return i - 7;
208 }
209
210 if (mp->bytes_left == 0) {
211 // Find length of this packet
212
213 /* Copy overread bytes from last frame into buffer. */
214 for(; mp->pc.overread>0; mp->pc.overread--) {
215 mp->pc.buffer[mp->pc.index++]= mp->pc.buffer[mp->pc.overread_index++];
216 }
217
218 if (mp->pc.index + buf_size < 2) {
219 ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
220 return buf_size;
221 }
222
223 mp->bytes_left = ((mp->pc.index > 0 ? mp->pc.buffer[0] : buf[0]) << 8)
224 | (mp->pc.index > 1 ? mp->pc.buffer[1] : buf[1-mp->pc.index]);
225 mp->bytes_left = (mp->bytes_left & 0xfff) * 2;
226 mp->bytes_left -= mp->pc.index;
227 }
228
229 next = (mp->bytes_left > buf_size) ? END_NOT_FOUND : mp->bytes_left;
230
231 if (ff_combine_frame(&mp->pc, next, &buf, &buf_size) < 0) {
232 mp->bytes_left -= buf_size;
233 return buf_size;
234 }
235
236 mp->bytes_left = 0;
237
238 sync_present = (AV_RB32(buf + 4) & 0xfffffffe) == 0xf8726fba;
239
240 if (!sync_present) {
241 // First nibble of a frame is a parity check of the first few nibbles.
242 // Only check when this isn't a sync frame - syncs have a checksum.
243
244 parity_bits = 0;
245 for (i = -1; i < mp->num_substreams; i++) {
246 parity_bits ^= buf[p++];
247 parity_bits ^= buf[p++];
248
249 if (i < 0 || buf[p-2] & 0x80) {
250 parity_bits ^= buf[p++];
251 parity_bits ^= buf[p++];
252 }
253 }
254
255 if ((((parity_bits >> 4) ^ parity_bits) & 0xF) != 0xF) {
256 av_log(avctx, AV_LOG_INFO, "mlpparse: Parity check failed.\n");
257 goto lost_sync;
258 }
259 } else {
260 GetBitContext gb;
261 MLPHeaderInfo mh;
262
263 init_get_bits(&gb, buf + 4, (buf_size - 4) << 3);
264 if (ff_mlp_read_major_sync(avctx, &mh, &gb) < 0)
265 goto lost_sync;
266
267 #ifdef CONFIG_AUDIO_NONSHORT
268 avctx->bits_per_sample = mh.group1_bits;
269 if (avctx->bits_per_sample > 16)
270 avctx->sample_fmt = SAMPLE_FMT_S32;
271 #endif
272 avctx->sample_rate = mh.group1_samplerate;
273 avctx->frame_size = mh.access_unit_size;
274
275 if (mh.stream_type == 0xbb) {
276 /* MLP stream */
277 avctx->channels = mlp_channels[mh.channels_mlp];
278 } else { /* mh.stream_type == 0xba */
279 /* TrueHD stream */
280 if (mh.channels_thd_stream2)
281 avctx->channels = truehd_channels(mh.channels_thd_stream2);
282 else
283 avctx->channels = truehd_channels(mh.channels_thd_stream1);
284 }
285
286 if (!mh.is_vbr) /* Stream is CBR */
287 avctx->bit_rate = mh.peak_bitrate;
288
289 mp->num_substreams = mh.num_substreams;
290 }
291
292 *poutbuf = buf;
293 *poutbuf_size = buf_size;
294
295 return next;
296
297 lost_sync:
298 mp->in_sync = 0;
299 return 1;
300 }
301
302 AVCodecParser mlp_parser = {
303 { CODEC_ID_MLP },
304 sizeof(MLPParseContext),
305 NULL,
306 mlp_parse,
307 NULL,
308 };