spdifdec.c
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1 /*
2  * IEC 61937 demuxer
3  * Copyright (c) 2010 Anssi Hannula <anssi.hannula at iki.fi>
4  *
5  * This file is part of Libav.
6  *
7  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
28 #include "avformat.h"
29 #include "spdif.h"
30 #include "libavcodec/ac3.h"
31 #include "libavcodec/aacadtsdec.h"
32 
34  enum IEC61937DataType data_type,
35  const char *buf, int *offset,
36  enum CodecID *codec)
37 {
38  AACADTSHeaderInfo aac_hdr;
39  GetBitContext gbc;
40 
41  switch (data_type & 0xff) {
42  case IEC61937_AC3:
43  *offset = AC3_FRAME_SIZE << 2;
44  *codec = CODEC_ID_AC3;
45  break;
47  *offset = spdif_mpeg_pkt_offset[1][0];
48  *codec = CODEC_ID_MP1;
49  break;
51  *offset = spdif_mpeg_pkt_offset[1][0];
52  *codec = CODEC_ID_MP3;
53  break;
54  case IEC61937_MPEG2_EXT:
55  *offset = 4608;
56  *codec = CODEC_ID_MP3;
57  break;
58  case IEC61937_MPEG2_AAC:
59  init_get_bits(&gbc, buf, AAC_ADTS_HEADER_SIZE * 8);
60  if (avpriv_aac_parse_header(&gbc, &aac_hdr)) {
61  if (s) /* be silent during a probe */
62  av_log(s, AV_LOG_ERROR, "Invalid AAC packet in IEC 61937\n");
63  return AVERROR_INVALIDDATA;
64  }
65  *offset = aac_hdr.samples << 2;
66  *codec = CODEC_ID_AAC;
67  break;
69  *offset = spdif_mpeg_pkt_offset[0][0];
70  *codec = CODEC_ID_MP1;
71  break;
73  *offset = spdif_mpeg_pkt_offset[0][1];
74  *codec = CODEC_ID_MP2;
75  break;
77  *offset = spdif_mpeg_pkt_offset[0][2];
78  *codec = CODEC_ID_MP3;
79  break;
80  case IEC61937_DTS1:
81  *offset = 2048;
82  *codec = CODEC_ID_DTS;
83  break;
84  case IEC61937_DTS2:
85  *offset = 4096;
86  *codec = CODEC_ID_DTS;
87  break;
88  case IEC61937_DTS3:
89  *offset = 8192;
90  *codec = CODEC_ID_DTS;
91  break;
92  default:
93  if (s) { /* be silent during a probe */
94  av_log(s, AV_LOG_WARNING, "Data type 0x%04x", data_type);
95  av_log_missing_feature(s, " in IEC 61937 is", 1);
96  }
97  return AVERROR_PATCHWELCOME;
98  }
99  return 0;
100 }
101 
102 /* Largest offset between bursts we currently handle, i.e. AAC with
103  aac_hdr.samples = 4096 */
104 #define SPDIF_MAX_OFFSET 16384
105 
106 static int spdif_probe(AVProbeData *p)
107 {
108  const uint8_t *buf = p->buf;
109  const uint8_t *probe_end = p->buf + FFMIN(2 * SPDIF_MAX_OFFSET, p->buf_size - 1);
110  const uint8_t *expected_code = buf + 7;
111  uint32_t state = 0;
112  int sync_codes = 0;
113  int consecutive_codes = 0;
114  int offset;
115  enum CodecID codec;
116 
117  for (; buf < probe_end; buf++) {
118  state = (state << 8) | *buf;
119 
120  if (state == (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))
121  && buf[1] < 0x37) {
122  sync_codes++;
123 
124  if (buf == expected_code) {
125  if (++consecutive_codes >= 2)
126  return AVPROBE_SCORE_MAX;
127  } else
128  consecutive_codes = 0;
129 
130  if (buf + 4 + AAC_ADTS_HEADER_SIZE > p->buf + p->buf_size)
131  break;
132 
133  /* continue probing to find more sync codes */
134  probe_end = FFMIN(buf + SPDIF_MAX_OFFSET, p->buf + p->buf_size - 1);
135 
136  /* skip directly to the next sync code */
137  if (!spdif_get_offset_and_codec(NULL, (buf[2] << 8) | buf[1],
138  &buf[5], &offset, &codec)) {
139  if (buf + offset >= p->buf + p->buf_size)
140  break;
141  expected_code = buf + offset;
142  buf = expected_code - 7;
143  }
144  }
145  }
146 
147  if (!sync_codes)
148  return 0;
149 
150  if (sync_codes >= 6)
151  /* good amount of sync codes but with unexpected offsets */
152  return AVPROBE_SCORE_MAX / 2;
153 
154  /* some sync codes were found */
155  return AVPROBE_SCORE_MAX / 8;
156 }
157 
159 {
161  return 0;
162 }
163 
165 {
166  AVIOContext *pb = s->pb;
167  enum IEC61937DataType data_type;
168  enum CodecID codec_id;
169  uint32_t state = 0;
170  int pkt_size_bits, offset, ret;
171 
172  while (state != (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))) {
173  state = (state << 8) | avio_r8(pb);
174  if (pb->eof_reached)
175  return AVERROR_EOF;
176  }
177 
178  data_type = avio_rl16(pb);
179  pkt_size_bits = avio_rl16(pb);
180 
181  if (pkt_size_bits % 16)
182  av_log_ask_for_sample(s, "Packet does not end to a 16-bit boundary.");
183 
184  ret = av_new_packet(pkt, FFALIGN(pkt_size_bits, 16) >> 3);
185  if (ret)
186  return ret;
187 
188  pkt->pos = avio_tell(pb) - BURST_HEADER_SIZE;
189 
190  if (avio_read(pb, pkt->data, pkt->size) < pkt->size) {
191  av_free_packet(pkt);
192  return AVERROR_EOF;
193  }
194  ff_spdif_bswap_buf16((uint16_t *)pkt->data, (uint16_t *)pkt->data, pkt->size >> 1);
195 
196  ret = spdif_get_offset_and_codec(s, data_type, pkt->data,
197  &offset, &codec_id);
198  if (ret) {
199  av_free_packet(pkt);
200  return ret;
201  }
202 
203  /* skip over the padding to the beginning of the next frame */
204  avio_skip(pb, offset - pkt->size - BURST_HEADER_SIZE);
205 
206  if (!s->nb_streams) {
207  /* first packet, create a stream */
209  if (!st) {
210  av_free_packet(pkt);
211  return AVERROR(ENOMEM);
212  }
214  st->codec->codec_id = codec_id;
215  } else if (codec_id != s->streams[0]->codec->codec_id) {
216  av_log_missing_feature(s, "codec change in IEC 61937", 0);
217  return AVERROR_PATCHWELCOME;
218  }
219 
220  if (!s->bit_rate && s->streams[0]->codec->sample_rate)
221  /* stream bitrate matches 16-bit stereo PCM bitrate for currently
222  supported codecs */
223  s->bit_rate = 2 * 16 * s->streams[0]->codec->sample_rate;
224 
225  return 0;
226 }
227 
229  .name = "spdif",
230  .long_name = NULL_IF_CONFIG_SMALL("IEC 61937 (compressed data in S/PDIF)"),
231  .read_probe = spdif_probe,
232  .read_header = spdif_read_header,
233  .read_packet = spdif_read_packet,
234  .flags = AVFMT_GENERIC_INDEX,
235 };