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vorbis_parser.c
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1 /*
2  * Copyright (c) 2012 Justin Ruggles
3  *
4  * This file is part of Libav.
5  *
6  * Libav is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * Libav is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with Libav; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 /**
22  * @file
23  * Vorbis audio parser
24  *
25  * Determines the duration for each packet.
26  */
27 
28 #include "get_bits.h"
29 #include "parser.h"
30 #include "xiph.h"
31 #include "vorbis_parser.h"
32 
34  const uint8_t *buf, int buf_size)
35 {
36  /* Id header should be 30 bytes */
37  if (buf_size < 30) {
38  av_log(avctx, AV_LOG_ERROR, "Id header is too short\n");
39  return AVERROR_INVALIDDATA;
40  }
41 
42  /* make sure this is the Id header */
43  if (buf[0] != 1) {
44  av_log(avctx, AV_LOG_ERROR, "Wrong packet type in Id header\n");
45  return AVERROR_INVALIDDATA;
46  }
47 
48  /* check for header signature */
49  if (memcmp(&buf[1], "vorbis", 6)) {
50  av_log(avctx, AV_LOG_ERROR, "Invalid packet signature in Id header\n");
51  return AVERROR_INVALIDDATA;
52  }
53 
54  if (!(buf[29] & 0x1)) {
55  av_log(avctx, AV_LOG_ERROR, "Invalid framing bit in Id header\n");
56  return AVERROR_INVALIDDATA;
57  }
58 
59  s->blocksize[0] = 1 << (buf[28] & 0xF);
60  s->blocksize[1] = 1 << (buf[28] >> 4);
61 
62  return 0;
63 }
64 
66  const uint8_t *buf, int buf_size)
67 {
68  GetBitContext gb, gb0;
69  uint8_t *rev_buf;
70  int i, ret = 0;
71  int got_framing_bit, mode_count, got_mode_header, last_mode_count = 0;
72 
73  /* avoid overread */
74  if (buf_size < 7) {
75  av_log(avctx, AV_LOG_ERROR, "Setup header is too short\n");
76  return AVERROR_INVALIDDATA;
77  }
78 
79  /* make sure this is the Setup header */
80  if (buf[0] != 5) {
81  av_log(avctx, AV_LOG_ERROR, "Wrong packet type in Setup header\n");
82  return AVERROR_INVALIDDATA;
83  }
84 
85  /* check for header signature */
86  if (memcmp(&buf[1], "vorbis", 6)) {
87  av_log(avctx, AV_LOG_ERROR, "Invalid packet signature in Setup header\n");
88  return AVERROR_INVALIDDATA;
89  }
90 
91  /* reverse bytes so we can easily read backwards with get_bits() */
92  if (!(rev_buf = av_malloc(buf_size))) {
93  av_log(avctx, AV_LOG_ERROR, "Out of memory\n");
94  return AVERROR(ENOMEM);
95  }
96  for (i = 0; i < buf_size; i++)
97  rev_buf[i] = buf[buf_size - 1 - i];
98  init_get_bits(&gb, rev_buf, buf_size * 8);
99 
100  got_framing_bit = 0;
101  while (get_bits_left(&gb) > 97) {
102  if (get_bits1(&gb)) {
103  got_framing_bit = get_bits_count(&gb);
104  break;
105  }
106  }
107  if (!got_framing_bit) {
108  av_log(avctx, AV_LOG_ERROR, "Invalid Setup header\n");
109  ret = AVERROR_INVALIDDATA;
110  goto bad_header;
111  }
112 
113  /* Now we search backwards to find possible valid mode counts. This is not
114  * fool-proof because we could have false positive matches and read too
115  * far, but there isn't really any way to be sure without parsing through
116  * all the many variable-sized fields before the modes. This approach seems
117  * to work well in testing, and it is similar to how it is handled in
118  * liboggz. */
119  mode_count = 0;
120  got_mode_header = 0;
121  while (get_bits_left(&gb) >= 97) {
122  if (get_bits(&gb, 8) > 63 || get_bits(&gb, 16) || get_bits(&gb, 16))
123  break;
124  skip_bits(&gb, 1);
125  mode_count++;
126  if (mode_count > 64)
127  break;
128  gb0 = gb;
129  if (get_bits(&gb0, 6) + 1 == mode_count) {
130  got_mode_header = 1;
131  last_mode_count = mode_count;
132  }
133  }
134  if (!got_mode_header) {
135  av_log(avctx, AV_LOG_ERROR, "Invalid Setup header\n");
136  ret = AVERROR_INVALIDDATA;
137  goto bad_header;
138  }
139  /* All samples I've seen use <= 2 modes, so ask for a sample if we find
140  * more than that, as it is most likely a false positive. If we get any
141  * we may need to approach this the long way and parse the whole Setup
142  * header, but I hope very much that it never comes to that. */
143  if (last_mode_count > 2) {
144  av_log_ask_for_sample(avctx, "%d modes found. This is either a false "
145  "positive or a sample from an unknown encoder.\n",
146  last_mode_count);
147  }
148  /* We're limiting the mode count to 63 so that we know that the previous
149  * block flag will be in the first packet byte. */
150  if (last_mode_count > 63) {
151  av_log(avctx, AV_LOG_ERROR, "Unsupported mode count: %d\n",
152  last_mode_count);
153  ret = AVERROR_INVALIDDATA;
154  goto bad_header;
155  }
156  s->mode_count = mode_count = last_mode_count;
157  /* Determine the number of bits required to code the mode and turn that
158  * into a bitmask to directly access the mode from the first frame byte. */
159  s->mode_mask = ((1 << (av_log2(mode_count - 1) + 1)) - 1) << 1;
160  /* The previous window flag is the next bit after the mode */
161  s->prev_mask = (s->mode_mask | 0x1) + 1;
162 
163  init_get_bits(&gb, rev_buf, buf_size * 8);
164  skip_bits_long(&gb, got_framing_bit);
165  for (i = mode_count - 1; i >= 0; i--) {
166  skip_bits_long(&gb, 40);
167  s->mode_blocksize[i] = get_bits1(&gb);
168  }
169 
170 bad_header:
171  av_free(rev_buf);
172  return ret;
173 }
174 
176 {
177  uint8_t *header_start[3];
178  int header_len[3];
179  int ret;
180 
181  s->avctx = avctx;
182  s->extradata_parsed = 1;
183 
184  if ((ret = avpriv_split_xiph_headers(avctx->extradata,
185  avctx->extradata_size, 30,
186  header_start, header_len)) < 0) {
187  av_log(avctx, AV_LOG_ERROR, "Extradata corrupt.\n");
188  return ret;
189  }
190 
191  if ((ret = parse_id_header(avctx, s, header_start[0], header_len[0])) < 0)
192  return ret;
193 
194  if ((ret = parse_setup_header(avctx, s, header_start[2], header_len[2])) < 0)
195  return ret;
196 
197  s->valid_extradata = 1;
199 
200  return 0;
201 }
202 
204  int buf_size)
205 {
206  int duration = 0;
207 
208  if (s->valid_extradata && buf_size > 0) {
209  int mode, current_blocksize;
210  int previous_blocksize = s->previous_blocksize;
211 
212  if (buf[0] & 1) {
213  av_log(s->avctx, AV_LOG_ERROR, "Invalid packet\n");
214  return AVERROR_INVALIDDATA;
215  }
216  if (s->mode_count == 1)
217  mode = 0;
218  else
219  mode = (buf[0] & s->mode_mask) >> 1;
220  if (mode >= s->mode_count) {
221  av_log(s->avctx, AV_LOG_ERROR, "Invalid mode in packet\n");
222  return AVERROR_INVALIDDATA;
223  }
224  if(s->mode_blocksize[mode]){
225  int flag = !!(buf[0] & s->prev_mask);
226  previous_blocksize = s->blocksize[flag];
227  }
228  current_blocksize = s->blocksize[s->mode_blocksize[mode]];
229  duration = (previous_blocksize + current_blocksize) >> 2;
230  s->previous_blocksize = current_blocksize;
231  }
232 
233  return duration;
234 }
235 
237 {
238  if (s->valid_extradata)
239  s->previous_blocksize = s->blocksize[0];
240 }
241 
242 #if CONFIG_VORBIS_PARSER
243 static int vorbis_parse(AVCodecParserContext *s1, AVCodecContext *avctx,
244  const uint8_t **poutbuf, int *poutbuf_size,
245  const uint8_t *buf, int buf_size)
246 {
247  VorbisParseContext *s = s1->priv_data;
248  int duration;
249 
250  if (!s->extradata_parsed && avctx->extradata && avctx->extradata_size)
251  if (avpriv_vorbis_parse_extradata(avctx, s))
252  goto end;
253 
254  if ((duration = avpriv_vorbis_parse_frame(s, buf, buf_size)) >= 0)
255  s1->duration = duration;
256 
257 end:
258  /* always return the full packet. this parser isn't doing any splitting or
259  combining, only packet analysis */
260  *poutbuf = buf;
261  *poutbuf_size = buf_size;
262  return buf_size;
263 }
264 
265 AVCodecParser ff_vorbis_parser = {
267  .priv_data_size = sizeof(VorbisParseContext),
268  .parser_parse = vorbis_parse,
269 };
270 #endif /* CONFIG_VORBIS_PARSER */