3 * Copyright (c) 2010 Anssi Hannula <anssi.hannula at iki.fi>
5 * This file is part of FFmpeg.
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.
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.
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
24 * IEC 61937 demuxer, used for compressed data in S/PDIF
25 * @author Anssi Hannula
28 #include "libavutil/bswap.h"
30 #include "libavcodec/ac3.h"
31 #include "libavcodec/adts_parser.h"
36 static int spdif_get_offset_and_codec(AVFormatContext *s,
37 enum IEC61937DataType data_type,
38 const char *buf, int *offset,
39 enum AVCodecID *codec)
45 switch (data_type & 0xff) {
47 *offset = AC3_FRAME_SIZE << 2;
48 *codec = AV_CODEC_ID_AC3;
50 case IEC61937_MPEG1_LAYER1:
51 *offset = spdif_mpeg_pkt_offset[1][0];
52 *codec = AV_CODEC_ID_MP1;
54 case IEC61937_MPEG1_LAYER23:
55 *offset = spdif_mpeg_pkt_offset[1][0];
56 *codec = AV_CODEC_ID_MP3;
58 case IEC61937_MPEG2_EXT:
60 *codec = AV_CODEC_ID_MP3;
62 case IEC61937_MPEG2_AAC:
63 ret = av_adts_header_parse(buf, &samples, &frames);
65 if (s) /* be silent during a probe */
66 av_log(s, AV_LOG_ERROR, "Invalid AAC packet in IEC 61937\n");
69 *offset = samples << 2;
70 *codec = AV_CODEC_ID_AAC;
72 case IEC61937_MPEG2_LAYER1_LSF:
73 *offset = spdif_mpeg_pkt_offset[0][0];
74 *codec = AV_CODEC_ID_MP1;
76 case IEC61937_MPEG2_LAYER2_LSF:
77 *offset = spdif_mpeg_pkt_offset[0][1];
78 *codec = AV_CODEC_ID_MP2;
80 case IEC61937_MPEG2_LAYER3_LSF:
81 *offset = spdif_mpeg_pkt_offset[0][2];
82 *codec = AV_CODEC_ID_MP3;
86 *codec = AV_CODEC_ID_DTS;
90 *codec = AV_CODEC_ID_DTS;
94 *codec = AV_CODEC_ID_DTS;
97 if (s) { /* be silent during a probe */
98 avpriv_request_sample(s, "Data type 0x%04x in IEC 61937",
101 return AVERROR_PATCHWELCOME;
106 /* Largest offset between bursts we currently handle, i.e. AAC with
108 #define SPDIF_MAX_OFFSET 16384
110 static int spdif_probe(AVProbeData *p)
112 enum AVCodecID codec;
113 return ff_spdif_probe (p->buf, p->buf_size, &codec);
116 int ff_spdif_probe(const uint8_t *p_buf, int buf_size, enum AVCodecID *codec)
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;
123 int consecutive_codes = 0;
126 for (; buf < probe_end; buf++) {
127 state = (state << 8) | *buf;
129 if (state == (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))
133 if (buf == expected_code) {
134 if (++consecutive_codes >= 2)
135 return AVPROBE_SCORE_MAX;
137 consecutive_codes = 0;
139 if (buf + 4 + AV_AAC_ADTS_HEADER_SIZE > p_buf + buf_size)
142 /* continue probing to find more sync codes */
143 probe_end = FFMIN(buf + SPDIF_MAX_OFFSET, p_buf + buf_size - 1);
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)
150 expected_code = buf + offset;
151 buf = expected_code - 7;
160 /* good amount of sync codes but with unexpected offsets */
161 return AVPROBE_SCORE_EXTENSION;
163 /* some sync codes were found */
164 return AVPROBE_SCORE_EXTENSION / 4;
167 static int spdif_read_header(AVFormatContext *s)
169 s->ctx_flags |= AVFMTCTX_NOHEADER;
173 int ff_spdif_read_packet(AVFormatContext *s, AVPacket *pkt)
175 AVIOContext *pb = s->pb;
176 enum IEC61937DataType data_type;
177 enum AVCodecID codec_id;
179 int pkt_size_bits, offset, ret;
181 while (state != (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))) {
182 state = (state << 8) | avio_r8(pb);
187 data_type = avio_rl16(pb);
188 pkt_size_bits = avio_rl16(pb);
190 if (pkt_size_bits % 16)
191 avpriv_request_sample(s, "Packet not ending at a 16-bit boundary");
193 ret = av_new_packet(pkt, FFALIGN(pkt_size_bits, 16) >> 3);
197 pkt->pos = avio_tell(pb) - BURST_HEADER_SIZE;
199 if (avio_read(pb, pkt->data, pkt->size) < pkt->size) {
200 av_packet_unref(pkt);
203 ff_spdif_bswap_buf16((uint16_t *)pkt->data, (uint16_t *)pkt->data, pkt->size >> 1);
205 ret = spdif_get_offset_and_codec(s, data_type, pkt->data,
208 av_packet_unref(pkt);
212 /* skip over the padding to the beginning of the next frame */
213 avio_skip(pb, offset - pkt->size - BURST_HEADER_SIZE);
215 if (!s->nb_streams) {
216 /* first packet, create a stream */
217 AVStream *st = avformat_new_stream(s, NULL);
219 av_packet_unref(pkt);
220 return AVERROR(ENOMEM);
222 st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
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;
229 if (!s->bit_rate && s->streams[0]->codecpar->sample_rate)
230 /* stream bitrate matches 16-bit stereo PCM bitrate for currently
232 s->bit_rate = 2 * 16 * s->streams[0]->codecpar->sample_rate;
237 AVInputFormat ff_spdif_demuxer = {
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,