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 "avformat.h"
29#include "spdif.h"
30#include "libavcodec/ac3.h"
31#include "libavcodec/aacadtsdec.h"
32
33static int spdif_get_offset_and_codec(AVFormatContext *s,
34                                      enum IEC61937DataType data_type,
35                                      const char *buf, int *offset,
36                                      enum AVCodecID *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 = AV_CODEC_ID_AC3;
45        break;
46    case IEC61937_MPEG1_LAYER1:
47        *offset = spdif_mpeg_pkt_offset[1][0];
48        *codec = AV_CODEC_ID_MP1;
49        break;
50    case IEC61937_MPEG1_LAYER23:
51        *offset = spdif_mpeg_pkt_offset[1][0];
52        *codec = AV_CODEC_ID_MP3;
53        break;
54    case IEC61937_MPEG2_EXT:
55        *offset = 4608;
56        *codec = AV_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) < 0) {
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 = AV_CODEC_ID_AAC;
67        break;
68    case IEC61937_MPEG2_LAYER1_LSF:
69        *offset = spdif_mpeg_pkt_offset[0][0];
70        *codec = AV_CODEC_ID_MP1;
71        break;
72    case IEC61937_MPEG2_LAYER2_LSF:
73        *offset = spdif_mpeg_pkt_offset[0][1];
74        *codec = AV_CODEC_ID_MP2;
75        break;
76    case IEC61937_MPEG2_LAYER3_LSF:
77        *offset = spdif_mpeg_pkt_offset[0][2];
78        *codec = AV_CODEC_ID_MP3;
79        break;
80    case IEC61937_DTS1:
81        *offset = 2048;
82        *codec = AV_CODEC_ID_DTS;
83        break;
84    case IEC61937_DTS2:
85        *offset = 4096;
86        *codec = AV_CODEC_ID_DTS;
87        break;
88    case IEC61937_DTS3:
89        *offset = 8192;
90        *codec = AV_CODEC_ID_DTS;
91        break;
92    default:
93        if (s) { /* be silent during a probe */
94            avpriv_request_sample(s, "Data type 0x%04x in IEC 61937",
95                                  data_type);
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
106static int spdif_probe(AVProbeData *p)
107{
108    enum AVCodecID codec;
109    return ff_spdif_probe (p->buf, p->buf_size, &codec);
110}
111
112int ff_spdif_probe(const uint8_t *p_buf, int buf_size, enum AVCodecID *codec)
113{
114    const uint8_t *buf = p_buf;
115    const uint8_t *probe_end = p_buf + FFMIN(2 * SPDIF_MAX_OFFSET, buf_size - 1);
116    const uint8_t *expected_code = buf + 7;
117    uint32_t state = 0;
118    int sync_codes = 0;
119    int consecutive_codes = 0;
120    int offset;
121
122    for (; buf < probe_end; buf++) {
123        state = (state << 8) | *buf;
124
125        if (state == (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))
126                && buf[1] < 0x37) {
127            sync_codes++;
128
129            if (buf == expected_code) {
130                if (++consecutive_codes >= 2)
131                    return AVPROBE_SCORE_MAX;
132            } else
133                consecutive_codes = 0;
134
135            if (buf + 4 + AAC_ADTS_HEADER_SIZE > p_buf + buf_size)
136                break;
137
138            /* continue probing to find more sync codes */
139            probe_end = FFMIN(buf + SPDIF_MAX_OFFSET, p_buf + buf_size - 1);
140
141            /* skip directly to the next sync code */
142            if (!spdif_get_offset_and_codec(NULL, (buf[2] << 8) | buf[1],
143                                            &buf[5], &offset, codec)) {
144                if (buf + offset >= p_buf + buf_size)
145                    break;
146                expected_code = buf + offset;
147                buf = expected_code - 7;
148            }
149        }
150    }
151
152    if (!sync_codes)
153        return 0;
154
155    if (sync_codes >= 6)
156        /* good amount of sync codes but with unexpected offsets */
157        return AVPROBE_SCORE_EXTENSION;
158
159    /* some sync codes were found */
160    return AVPROBE_SCORE_EXTENSION / 4;
161}
162
163static int spdif_read_header(AVFormatContext *s)
164{
165    s->ctx_flags |= AVFMTCTX_NOHEADER;
166    return 0;
167}
168
169int ff_spdif_read_packet(AVFormatContext *s, AVPacket *pkt)
170{
171    AVIOContext *pb = s->pb;
172    enum IEC61937DataType data_type;
173    enum AVCodecID codec_id;
174    uint32_t state = 0;
175    int pkt_size_bits, offset, ret;
176
177    while (state != (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))) {
178        state = (state << 8) | avio_r8(pb);
179        if (url_feof(pb))
180            return AVERROR_EOF;
181    }
182
183    data_type = avio_rl16(pb);
184    pkt_size_bits = avio_rl16(pb);
185
186    if (pkt_size_bits % 16)
187        avpriv_request_sample(s, "Packet not ending at a 16-bit boundary");
188
189    ret = av_new_packet(pkt, FFALIGN(pkt_size_bits, 16) >> 3);
190    if (ret)
191        return ret;
192
193    pkt->pos = avio_tell(pb) - BURST_HEADER_SIZE;
194
195    if (avio_read(pb, pkt->data, pkt->size) < pkt->size) {
196        av_free_packet(pkt);
197        return AVERROR_EOF;
198    }
199    ff_spdif_bswap_buf16((uint16_t *)pkt->data, (uint16_t *)pkt->data, pkt->size >> 1);
200
201    ret = spdif_get_offset_and_codec(s, data_type, pkt->data,
202                                     &offset, &codec_id);
203    if (ret) {
204        av_free_packet(pkt);
205        return ret;
206    }
207
208    /* skip over the padding to the beginning of the next frame */
209    avio_skip(pb, offset - pkt->size - BURST_HEADER_SIZE);
210
211    if (!s->nb_streams) {
212        /* first packet, create a stream */
213        AVStream *st = avformat_new_stream(s, NULL);
214        if (!st) {
215            av_free_packet(pkt);
216            return AVERROR(ENOMEM);
217        }
218        st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
219        st->codec->codec_id = codec_id;
220    } else if (codec_id != s->streams[0]->codec->codec_id) {
221        avpriv_report_missing_feature(s, "Codec change in IEC 61937");
222        return AVERROR_PATCHWELCOME;
223    }
224
225    if (!s->bit_rate && s->streams[0]->codec->sample_rate)
226        /* stream bitrate matches 16-bit stereo PCM bitrate for currently
227           supported codecs */
228        s->bit_rate = 2 * 16 * s->streams[0]->codec->sample_rate;
229
230    return 0;
231}
232
233AVInputFormat ff_spdif_demuxer = {
234    .name           = "spdif",
235    .long_name      = NULL_IF_CONFIG_SMALL("IEC 61937 (compressed data in S/PDIF)"),
236    .read_probe     = spdif_probe,
237    .read_header    = spdif_read_header,
238    .read_packet    = ff_spdif_read_packet,
239    .flags          = AVFMT_GENERIC_INDEX,
240};
241