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mlp_parser.c
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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
24  * MLP parser
25  */
26 
27 #include <stdint.h>
28 
30 #include "libavutil/crc.h"
31 #include "get_bits.h"
32 #include "parser.h"
33 #include "mlp_parser.h"
34 #include "mlp.h"
35 
36 static const uint8_t mlp_quants[16] = {
37  16, 20, 24, 0, 0, 0, 0, 0,
38  0, 0, 0, 0, 0, 0, 0, 0,
39 };
40 
41 static const uint8_t mlp_channels[32] = {
42  1, 2, 3, 4, 3, 4, 5, 3, 4, 5, 4, 5, 6, 4, 5, 4,
43  5, 6, 5, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
44 };
45 
46 const uint64_t ff_mlp_layout[32] = {
51  AV_CH_LAYOUT_STEREO|AV_CH_LOW_FREQUENCY,
52  AV_CH_LAYOUT_2_1|AV_CH_LOW_FREQUENCY,
53  AV_CH_LAYOUT_QUAD|AV_CH_LOW_FREQUENCY,
57  AV_CH_LAYOUT_SURROUND|AV_CH_LOW_FREQUENCY,
58  AV_CH_LAYOUT_4POINT0|AV_CH_LOW_FREQUENCY,
62  AV_CH_LAYOUT_SURROUND|AV_CH_LOW_FREQUENCY,
63  AV_CH_LAYOUT_4POINT0|AV_CH_LOW_FREQUENCY,
65  AV_CH_LAYOUT_QUAD|AV_CH_LOW_FREQUENCY,
68  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
69 };
70 
71 static const uint8_t thd_chancount[13] = {
72 // LR C LFE LRs LRvh LRc LRrs Cs Ts LRsd LRw Cvh LFE2
73  2, 1, 1, 2, 2, 2, 2, 1, 1, 2, 2, 1, 1
74 };
75 
76 static const uint64_t thd_layout[13] = {
78  AV_CH_FRONT_CENTER, // C
79  AV_CH_LOW_FREQUENCY, // LFE
84  AV_CH_BACK_CENTER, // Cs
85  AV_CH_TOP_CENTER, // Ts
89  AV_CH_LOW_FREQUENCY_2, // LFE2
90 };
91 
92 static int mlp_samplerate(int in)
93 {
94  if (in == 0xF)
95  return 0;
96 
97  return (in & 8 ? 44100 : 48000) << (in & 7) ;
98 }
99 
100 static int truehd_channels(int chanmap)
101 {
102  int channels = 0, i;
103 
104  for (i = 0; i < 13; i++)
105  channels += thd_chancount[i] * ((chanmap >> i) & 1);
106 
107  return channels;
108 }
109 
110 uint64_t ff_truehd_layout(int chanmap)
111 {
112  int i;
113  uint64_t layout = 0;
114 
115  for (i = 0; i < 13; i++)
116  layout |= thd_layout[i] * ((chanmap >> i) & 1);
117 
118  return layout;
119 }
120 
121 /** Read a major sync info header - contains high level information about
122  * the stream - sample rate, channel arrangement etc. Most of this
123  * information is not actually necessary for decoding, only for playback.
124  * gb must be a freshly initialized GetBitContext with no bits read.
125  */
126 
128 {
129  int ratebits, channel_arrangement;
130  uint16_t checksum;
131 
132  av_assert1(get_bits_count(gb) == 0);
133 
134  if (gb->size_in_bits < 28 << 3) {
135  av_log(log, AV_LOG_ERROR, "packet too short, unable to read major sync\n");
136  return -1;
137  }
138 
139  checksum = ff_mlp_checksum16(gb->buffer, 26);
140  if (checksum != AV_RL16(gb->buffer+26)) {
141  av_log(log, AV_LOG_ERROR, "major sync info header checksum error\n");
142  return AVERROR_INVALIDDATA;
143  }
144 
145  if (get_bits_long(gb, 24) != 0xf8726f) /* Sync words */
146  return AVERROR_INVALIDDATA;
147 
148  mh->stream_type = get_bits(gb, 8);
149 
150  if (mh->stream_type == 0xbb) {
151  mh->group1_bits = mlp_quants[get_bits(gb, 4)];
152  mh->group2_bits = mlp_quants[get_bits(gb, 4)];
153 
154  ratebits = get_bits(gb, 4);
155  mh->group1_samplerate = mlp_samplerate(ratebits);
157 
158  skip_bits(gb, 11);
159 
161  channel_arrangement = get_bits(gb, 5);
162  mh->channels_mlp = mlp_channels[channel_arrangement];
163  mh->channel_layout_mlp = ff_mlp_layout[channel_arrangement];
164  } else if (mh->stream_type == 0xba) {
165  mh->group1_bits = 24; // TODO: Is this information actually conveyed anywhere?
166  mh->group2_bits = 0;
167 
168  ratebits = get_bits(gb, 4);
169  mh->group1_samplerate = mlp_samplerate(ratebits);
170  mh->group2_samplerate = 0;
171 
172  skip_bits(gb, 8);
173 
175  channel_arrangement = get_bits(gb, 5);
176  mh->channels_thd_stream1 = truehd_channels(channel_arrangement);
177  mh->channel_layout_thd_stream1 = ff_truehd_layout(channel_arrangement);
178 
179  skip_bits(gb, 2);
180 
181  channel_arrangement = get_bits(gb, 13);
182  mh->channels_thd_stream2 = truehd_channels(channel_arrangement);
183  mh->channel_layout_thd_stream2 = ff_truehd_layout(channel_arrangement);
184  } else
185  return AVERROR_INVALIDDATA;
186 
187  mh->access_unit_size = 40 << (ratebits & 7);
188  mh->access_unit_size_pow2 = 64 << (ratebits & 7);
189 
190  skip_bits_long(gb, 48);
191 
192  mh->is_vbr = get_bits1(gb);
193 
194  mh->peak_bitrate = (get_bits(gb, 15) * mh->group1_samplerate + 8) >> 4;
195 
196  mh->num_substreams = get_bits(gb, 4);
197 
198  skip_bits_long(gb, 4 + 11 * 8);
199 
200  return 0;
201 }
202 
203 typedef struct MLPParseContext
204 {
206 
208 
209  int in_sync;
210 
213 
215 {
216  ff_mlp_init_crc();
217  return 0;
218 }
219 
221  AVCodecContext *avctx,
222  const uint8_t **poutbuf, int *poutbuf_size,
223  const uint8_t *buf, int buf_size)
224 {
225  MLPParseContext *mp = s->priv_data;
226  int sync_present;
227  uint8_t parity_bits;
228  int next;
229  int i, p = 0;
230 
231  *poutbuf_size = 0;
232  if (buf_size == 0)
233  return 0;
234 
235  if (!mp->in_sync) {
236  // Not in sync - find a major sync header
237 
238  for (i = 0; i < buf_size; i++) {
239  mp->pc.state = (mp->pc.state << 8) | buf[i];
240  if ((mp->pc.state & 0xfffffffe) == 0xf8726fba &&
241  // ignore if we do not have the data for the start of header
242  mp->pc.index + i >= 7) {
243  mp->in_sync = 1;
244  mp->bytes_left = 0;
245  break;
246  }
247  }
248 
249  if (!mp->in_sync) {
250  if (ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size) != -1)
251  av_log(avctx, AV_LOG_WARNING, "ff_combine_frame failed\n");
252  return buf_size;
253  }
254 
255  ff_combine_frame(&mp->pc, i - 7, &buf, &buf_size);
256 
257  return i - 7;
258  }
259 
260  if (mp->bytes_left == 0) {
261  // Find length of this packet
262 
263  /* Copy overread bytes from last frame into buffer. */
264  for(; mp->pc.overread>0; mp->pc.overread--) {
265  mp->pc.buffer[mp->pc.index++]= mp->pc.buffer[mp->pc.overread_index++];
266  }
267 
268  if (mp->pc.index + buf_size < 2) {
269  if (ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size) != -1)
270  av_log(avctx, AV_LOG_WARNING, "ff_combine_frame failed\n");
271  return buf_size;
272  }
273 
274  mp->bytes_left = ((mp->pc.index > 0 ? mp->pc.buffer[0] : buf[0]) << 8)
275  | (mp->pc.index > 1 ? mp->pc.buffer[1] : buf[1-mp->pc.index]);
276  mp->bytes_left = (mp->bytes_left & 0xfff) * 2;
277  if (mp->bytes_left <= 0) { // prevent infinite loop
278  goto lost_sync;
279  }
280  mp->bytes_left -= mp->pc.index;
281  }
282 
283  next = (mp->bytes_left > buf_size) ? END_NOT_FOUND : mp->bytes_left;
284 
285  if (ff_combine_frame(&mp->pc, next, &buf, &buf_size) < 0) {
286  mp->bytes_left -= buf_size;
287  return buf_size;
288  }
289 
290  mp->bytes_left = 0;
291 
292  sync_present = (AV_RB32(buf + 4) & 0xfffffffe) == 0xf8726fba;
293 
294  if (!sync_present) {
295  /* The first nibble of a frame is a parity check of the 4-byte
296  * access unit header and all the 2- or 4-byte substream headers. */
297  // Only check when this isn't a sync frame - syncs have a checksum.
298 
299  parity_bits = 0;
300  for (i = -1; i < mp->num_substreams; i++) {
301  parity_bits ^= buf[p++];
302  parity_bits ^= buf[p++];
303 
304  if (i < 0 || buf[p-2] & 0x80) {
305  parity_bits ^= buf[p++];
306  parity_bits ^= buf[p++];
307  }
308  }
309 
310  if ((((parity_bits >> 4) ^ parity_bits) & 0xF) != 0xF) {
311  av_log(avctx, AV_LOG_INFO, "mlpparse: Parity check failed.\n");
312  goto lost_sync;
313  }
314  } else {
315  GetBitContext gb;
317 
318  init_get_bits(&gb, buf + 4, (buf_size - 4) << 3);
319  if (ff_mlp_read_major_sync(avctx, &mh, &gb) < 0)
320  goto lost_sync;
321 
322  avctx->bits_per_raw_sample = mh.group1_bits;
323  if (avctx->bits_per_raw_sample > 16)
324  avctx->sample_fmt = AV_SAMPLE_FMT_S32;
325  else
326  avctx->sample_fmt = AV_SAMPLE_FMT_S16;
327  avctx->sample_rate = mh.group1_samplerate;
328  s->duration = mh.access_unit_size;
329 
330  if(!avctx->channels || !avctx->channel_layout) {
331  if (mh.stream_type == 0xbb) {
332  /* MLP stream */
333 #if FF_API_REQUEST_CHANNELS
334  if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
335  mh.num_substreams > 1) {
336  avctx->channels = 2;
338  } else
339 #endif
341  mh.num_substreams > 1) {
342  avctx->channels = 2;
344  } else {
345  avctx->channels = mh.channels_mlp;
347  }
348  } else { /* mh.stream_type == 0xba */
349  /* TrueHD stream */
350 #if FF_API_REQUEST_CHANNELS
351  if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
352  mh.num_substreams > 1) {
353  avctx->channels = 2;
355  } else if (avctx->request_channels > 0 &&
356  avctx->request_channels <= mh.channels_thd_stream1) {
357  avctx->channels = mh.channels_thd_stream1;
359  } else
360 #endif
362  mh.num_substreams > 1) {
363  avctx->channels = 2;
365  } else if (avctx->request_channel_layout == mh.channel_layout_thd_stream1 ||
366  !mh.channels_thd_stream2) {
367  avctx->channels = mh.channels_thd_stream1;
369  } else {
370  avctx->channels = mh.channels_thd_stream2;
372  }
373  }
374  }
375 
376  if (!mh.is_vbr) /* Stream is CBR */
377  avctx->bit_rate = mh.peak_bitrate;
378 
380  }
381 
382  *poutbuf = buf;
383  *poutbuf_size = buf_size;
384 
385  return next;
386 
387 lost_sync:
388  mp->in_sync = 0;
389  return 1;
390 }
391 
394  .priv_data_size = sizeof(MLPParseContext),
395  .parser_init = mlp_init,
396  .parser_parse = mlp_parse,
397  .parser_close = ff_parse_close,
398 };