FFmpeg: libavformat/spdifdec.c Source File

FFmpeg

[フレーム]

libavformat

spdifdec.c

Go to the documentation of this file.

1 /*

2 * IEC 61937 demuxer

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 */

22 /**

23 * @file

24 * IEC 61937 demuxer, used for compressed data in S/PDIF

25 * @author Anssi Hannula

26 */

28 #include "avformat.h"

29 #include "spdif.h"

30 #include "libavcodec/ac3.h"

31 #include "libavcodec/aacadtsdec.h"

33 static 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;

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)) {

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

106 static int spdif_probe(AVProbeData *p)

107 {

108 enum AVCodecID codec;

109 return ff_spdif_probe (p->buf, p->buf_size, &codec);

110 }

111

112 int 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

163 static int spdif_read_header(AVFormatContext *s)

164 {

165 s->ctx_flags |= AVFMTCTX_NOHEADER;

166 return 0;

167 }

168

169 int 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

233 AVInputFormat 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 };

Generated on Wed Jul 10 2013 23:48:14 for FFmpeg by doxygen 1.8.2