FFmpeg
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 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  * IEC 61937 demuxer, used for compressed data in S/PDIF
25  * @author Anssi Hannula
26  */
27 
28 #include "libavutil/bswap.h"
29 
30 #include "libavcodec/ac3.h"
31 #include "libavcodec/adts_parser.h"
32 
33 #include "avformat.h"
34 #include "spdif.h"
35 
37  enum IEC61937DataType data_type,
38  const char *buf, int *offset,
39  enum AVCodecID *codec)
40 {
41  uint32_t samples;
43  int ret;
44 
45  switch (data_type & 0xff) {
46  case IEC61937_AC3:
47  *offset = AC3_FRAME_SIZE << 2;
48  *codec = AV_CODEC_ID_AC3;
49  break;
51  *offset = spdif_mpeg_pkt_offset[1][0];
52  *codec = AV_CODEC_ID_MP1;
53  break;
55  *offset = spdif_mpeg_pkt_offset[1][0];
56  *codec = AV_CODEC_ID_MP3;
57  break;
58  case IEC61937_MPEG2_EXT:
59  *offset = 4608;
60  *codec = AV_CODEC_ID_MP3;
61  break;
62  case IEC61937_MPEG2_AAC:
63  ret = av_adts_header_parse(buf, &samples, &frames);
64  if (ret < 0) {
65  if (s) /* be silent during a probe */
66  av_log(s, AV_LOG_ERROR, "Invalid AAC packet in IEC 61937\n");
67  return ret;
68  }
69  *offset = samples << 2;
70  *codec = AV_CODEC_ID_AAC;
71  break;
73  *offset = spdif_mpeg_pkt_offset[0][0];
74  *codec = AV_CODEC_ID_MP1;
75  break;
77  *offset = spdif_mpeg_pkt_offset[0][1];
78  *codec = AV_CODEC_ID_MP2;
79  break;
81  *offset = spdif_mpeg_pkt_offset[0][2];
82  *codec = AV_CODEC_ID_MP3;
83  break;
84  case IEC61937_DTS1:
85  *offset = 2048;
86  *codec = AV_CODEC_ID_DTS;
87  break;
88  case IEC61937_DTS2:
89  *offset = 4096;
90  *codec = AV_CODEC_ID_DTS;
91  break;
92  case IEC61937_DTS3:
93  *offset = 8192;
94  *codec = AV_CODEC_ID_DTS;
95  break;
96  default:
97  if (s) { /* be silent during a probe */
98  avpriv_request_sample(s, "Data type 0x%04x in IEC 61937",
99  data_type);
100  }
101  return AVERROR_PATCHWELCOME;
102  }
103  return 0;
104 }
105 
106 /* Largest offset between bursts we currently handle, i.e. AAC with
107  samples = 4096 */
108 #define SPDIF_MAX_OFFSET 16384
109 
110 static int spdif_probe(const AVProbeData *p)
111 {
112  enum AVCodecID codec;
113  return ff_spdif_probe (p->buf, p->buf_size, &codec);
114 }
115 
116 int ff_spdif_probe(const uint8_t *p_buf, int buf_size, enum AVCodecID *codec)
117 {
118  const uint8_t *buf = p_buf;
119  const uint8_t *probe_end = p_buf + FFMIN(2 * SPDIF_MAX_OFFSET, buf_size - 1);
120  const uint8_t *expected_code = buf + 7;
121  uint32_t state = 0;
122  int sync_codes = 0;
123  int consecutive_codes = 0;
124  int offset;
125 
126  for (; buf < probe_end; buf++) {
127  state = (state << 8) | *buf;
128 
129  if (state == (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))
130  && buf[1] < 0x37) {
131  sync_codes++;
132 
133  if (buf == expected_code) {
134  if (++consecutive_codes >= 2)
135  return AVPROBE_SCORE_MAX;
136  } else
137  consecutive_codes = 0;
138 
139  if (buf + 4 + AV_AAC_ADTS_HEADER_SIZE > p_buf + buf_size)
140  break;
141 
142  /* continue probing to find more sync codes */
143  probe_end = FFMIN(buf + SPDIF_MAX_OFFSET, p_buf + buf_size - 1);
144 
145  /* skip directly to the next sync code */
146  if (!spdif_get_offset_and_codec(NULL, (buf[2] << 8) | buf[1],
147  &buf[5], &offset, codec)) {
148  if (buf + offset >= p_buf + buf_size)
149  break;
150  expected_code = buf + offset;
151  buf = expected_code - 7;
152  }
153  }
154  }
155 
156  if (!sync_codes)
157  return 0;
158 
159  if (sync_codes >= 6)
160  /* good amount of sync codes but with unexpected offsets */
162 
163  /* some sync codes were found */
164  return AVPROBE_SCORE_EXTENSION / 4;
165 }
166 
168 {
170  return 0;
171 }
172 
174 {
175  AVIOContext *pb = s->pb;
176  enum IEC61937DataType data_type;
177  enum AVCodecID codec_id;
178  uint32_t state = 0;
179  int pkt_size_bits, offset, ret;
180 
181  while (state != (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))) {
182  state = (state << 8) | avio_r8(pb);
183  if (avio_feof(pb))
184  return AVERROR_EOF;
185  }
186 
187  data_type = avio_rl16(pb);
188  pkt_size_bits = avio_rl16(pb);
189 
190  if (pkt_size_bits % 16)
191  avpriv_request_sample(s, "Packet not ending at a 16-bit boundary");
192 
193  ret = av_new_packet(pkt, FFALIGN(pkt_size_bits, 16) >> 3);
194  if (ret)
195  return ret;
196 
197  pkt->pos = avio_tell(pb) - BURST_HEADER_SIZE;
198 
199  if (avio_read(pb, pkt->data, pkt->size) < pkt->size) {
200  av_packet_unref(pkt);
201  return AVERROR_EOF;
202  }
203  ff_spdif_bswap_buf16((uint16_t *)pkt->data, (uint16_t *)pkt->data, pkt->size >> 1);
204 
205  ret = spdif_get_offset_and_codec(s, data_type, pkt->data,
206  &offset, &codec_id);
207  if (ret) {
208  av_packet_unref(pkt);
209  return ret;
210  }
211 
212  /* skip over the padding to the beginning of the next frame */
213  avio_skip(pb, offset - pkt->size - BURST_HEADER_SIZE);
214 
215  if (!s->nb_streams) {
216  /* first packet, create a stream */
218  if (!st) {
219  av_packet_unref(pkt);
220  return AVERROR(ENOMEM);
221  }
223  st->codecpar->codec_id = codec_id;
224  } else if (codec_id != s->streams[0]->codecpar->codec_id) {
225  avpriv_report_missing_feature(s, "Codec change in IEC 61937");
226  return AVERROR_PATCHWELCOME;
227  }
228 
229  if (!s->bit_rate && s->streams[0]->codecpar->sample_rate)
230  /* stream bitrate matches 16-bit stereo PCM bitrate for currently
231  supported codecs */
232  s->bit_rate = 2 * 16 * s->streams[0]->codecpar->sample_rate;
233 
234  return 0;
235 }
236 
238  .name = "spdif",
239  .long_name = NULL_IF_CONFIG_SMALL("IEC 61937 (compressed data in S/PDIF)"),
240  .read_probe = spdif_probe,
241  .read_header = spdif_read_header,
242  .read_packet = ff_spdif_read_packet,
243  .flags = AVFMT_GENERIC_INDEX,
244 };
static int spdif_get_offset_and_codec(AVFormatContext *s, enum IEC61937DataType data_type, const char *buf, int *offset, enum AVCodecID *codec)
Definition: spdifdec.c:36
#define NULL
Definition: coverity.c:32
Bytestream IO Context.
Definition: avio.h:161
int64_t pos
byte position in stream, -1 if unknown
Definition: avcodec.h:1500
#define BURST_HEADER_SIZE
Definition: spdif.h:30
MPEG-2, layer-1 low sampling frequency.
Definition: spdif.h:38
#define avpriv_request_sample(...)
enum AVCodecID codec_id
Definition: qsv.c:77
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: avcodec.h:3968
int size
Definition: avcodec.h:1481
static int spdif_read_header(AVFormatContext *s)
Definition: spdifdec.c:167
int64_t bit_rate
Total stream bitrate in bit/s, 0 if not available.
Definition: avformat.h:1480
IEC61937DataType
Definition: spdif.h:32
int64_t avio_skip(AVIOContext *s, int64_t offset)
Skip given number of bytes forward.
Definition: aviobuf.c:334
static AVPacket pkt
void ff_spdif_bswap_buf16(uint16_t *dst, const uint16_t *src, int w)
Definition: spdif.c:26
int ctx_flags
Flags signalling stream properties.
Definition: avformat.h:1407
if it could not because there are no more frames
int ff_spdif_probe(const uint8_t *p_buf, int buf_size, enum AVCodecID *codec)
Definition: spdifdec.c:116
Format I/O context.
Definition: avformat.h:1358
int av_adts_header_parse(const uint8_t *buf, uint32_t *samples, uint8_t *frames)
Extract the number of samples and frames from AAC data.
Definition: adts_parser.c:27
MPEG-2 AAC ADTS.
Definition: spdif.h:37
uint8_t
#define AVFMTCTX_NOHEADER
signal that no header is present (streams are added dynamically)
Definition: avformat.h:1302
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf offset
static int spdif_probe(const AVProbeData *p)
Definition: spdifdec.c:110
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
Definition: utils.c:4499
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1426
uint8_t * data
Definition: avcodec.h:1480
#define AVERROR_EOF
End of file.
Definition: error.h:55
DTS type II (1024 samples)
Definition: spdif.h:42
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:557
#define FFALIGN(x, a)
Definition: macros.h:48
#define av_log(a,...)
int avio_read(AVIOContext *s, unsigned char *buf, int size)
Read size bytes from AVIOContext into buf.
Definition: aviobuf.c:650
#define AV_BSWAP16C(x)
Definition: bswap.h:51
int av_new_packet(AVPacket *pkt, int size)
Allocate the payload of a packet and initialize its fields with default values.
Definition: avpacket.c:86
AVCodecID
Identify the syntax and semantics of the bitstream.
Definition: avcodec.h:215
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
DTS type III (2048 samples)
Definition: spdif.h:43
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:186
preferred ID for decoding MPEG audio layer 1, 2 or 3
Definition: avcodec.h:566
enum AVMediaType codec_type
General type of the encoded data.
Definition: avcodec.h:3964
MPEG-1 layer 2 or 3 data or MPEG-2 without extension.
Definition: spdif.h:35
MPEG-2, layer-3 low sampling frequency.
Definition: spdif.h:40
#define AV_AAC_ADTS_HEADER_SIZE
Definition: adts_parser.h:25
MPEG-1 layer 1.
Definition: spdif.h:34
int avio_r8(AVIOContext *s)
Definition: aviobuf.c:641
int buf_size
Size of buf except extra allocated bytes.
Definition: avformat.h:449
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:448
unsigned int nb_streams
Number of elements in AVFormatContext.streams.
Definition: avformat.h:1414
#define FFMIN(a, b)
Definition: common.h:96
#define SPDIF_MAX_OFFSET
Definition: spdifdec.c:108
#define s(width, name)
Definition: cbs_vp9.c:257
#define SYNCWORD2
Definition: spdif.h:29
Stream structure.
Definition: avformat.h:881
#define AVERROR_PATCHWELCOME
Not yet implemented in FFmpeg, patches welcome.
Definition: error.h:62
AVIOContext * pb
I/O context.
Definition: avformat.h:1400
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:599
void * buf
Definition: avisynth_c.h:766
#define AVFMT_GENERIC_INDEX
Use generic index building code.
Definition: avformat.h:468
byte swapping routines
#define AVPROBE_SCORE_EXTENSION
score for file extension
Definition: avformat.h:456
DTS type I (512 samples)
Definition: spdif.h:41
This structure contains the data a format has to probe a file.
Definition: avformat.h:446
void avpriv_report_missing_feature(void *avc, const char *msg,...) av_printf_format(2
Log a generic warning message about a missing feature.
MPEG-2, layer-2 low sampling frequency.
Definition: spdif.h:39
int sample_rate
Audio only.
Definition: avcodec.h:4078
#define AC3_FRAME_SIZE
Definition: ac3.h:38
#define AVPROBE_SCORE_MAX
maximum score
Definition: avformat.h:458
unsigned int avio_rl16(AVIOContext *s)
Definition: aviobuf.c:756
Main libavformat public API header.
MPEG-2 data with extension.
Definition: spdif.h:36
static const uint16_t spdif_mpeg_pkt_offset[2][3]
Definition: spdif.h:55
#define SYNCWORD1
Definition: spdif.h:28
static struct @316 state
AC-3 data.
Definition: spdif.h:33
Filter the word “frame” indicates either a video frame or a group of audio samples
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:654
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1028
int avio_feof(AVIOContext *s)
Similar to feof() but also returns nonzero on read errors.
Definition: aviobuf.c:361
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later.That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another.Frame references ownership and permissions
int ff_spdif_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: spdifdec.c:173
This structure stores compressed data.
Definition: avcodec.h:1457
Common code between the AC-3 encoder and decoder.
AVInputFormat ff_spdif_demuxer
Definition: spdifdec.c:237