FFmpeg: libavformat/ac3dec.c Source File

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libavformat

ac3dec.c

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1 /*

2 * RAW AC-3 and E-AC-3 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 #include "libavutil/crc.h"

23 #include "libavcodec/ac3_parser.h"

24 #include "avformat.h"

25 #include "rawdec.h"

27 static int ac3_eac3_probe(AVProbeData *p, enum AVCodecID expected_codec_id)

28 {

29 int max_frames, first_frames = 0, frames;

30 const uint8_t *buf, *buf2, *end;

31 AC3HeaderInfo hdr;

32 GetBitContext gbc;

33 enum AVCodecID codec_id = AV_CODEC_ID_AC3;

35 max_frames = 0;

36 buf = p->buf;

37 end = buf + p->buf_size;

39 for(; buf < end; buf++) {

40 if(buf > p->buf && !(buf[0] == 0x0B && buf[1] == 0x77)

41 && !(buf[0] == 0x77 && buf[1] == 0x0B) )

42 continue;

43 buf2 = buf;

45 for(frames = 0; buf2 < end; frames++) {

46 uint8_t buf3[4096];

47 int i;

48 if(!memcmp(buf2, "\x1\x100円0円0円0円0円0円", 8))

49 buf2+=16;

50 if (buf[0] == 0x77 && buf[1] == 0x0B) {

51 for(i=0; i<8; i+=2) {

52 buf3[i ] = buf[i+1];

53 buf3[i+1] = buf[i ];

54 }

55 init_get_bits(&gbc, buf3, 54);

56 }else

57 init_get_bits(&gbc, buf2, 54);

58 if(avpriv_ac3_parse_header(&gbc, &hdr) < 0)

59 break;

60 if(buf2 + hdr.frame_size > end)

61 break;

62 if (buf[0] == 0x77 && buf[1] == 0x0B) {

63 av_assert0(hdr.frame_size <= sizeof(buf3));

64 for(i=8; i<hdr.frame_size; i+=2) {

65 buf3[i ] = buf[i+1];

66 buf3[i+1] = buf[i ];

67 }

68 }

69 if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, gbc.buffer + 2, hdr.frame_size - 2))

70 break;

71 if (hdr.bitstream_id > 10)

72 codec_id = AV_CODEC_ID_EAC3;

73 buf2 += hdr.frame_size;

74 }

75 max_frames = FFMAX(max_frames, frames);

76 if(buf == p->buf)

77 first_frames = frames;

78 }

79 if(codec_id != expected_codec_id) return 0;

80 // keep this in sync with mp3 probe, both need to avoid

81 // issues with MPEG-files!

82 if (first_frames>=4) return AVPROBE_SCORE_EXTENSION + 1;

83 else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;

84 else if(max_frames>=4) return AVPROBE_SCORE_EXTENSION/2;

85 else if(max_frames>=1) return 1;

86 else return 0;

87 }

89 #if CONFIG_AC3_DEMUXER

90 static int ac3_probe(AVProbeData *p)

91 {

92 return ac3_eac3_probe(p, AV_CODEC_ID_AC3);

93 }

95 AVInputFormat ff_ac3_demuxer = {

96 .name = "ac3",

97 .long_name = NULL_IF_CONFIG_SMALL("raw AC-3"),

98 .read_probe = ac3_probe,

99 .read_header = ff_raw_audio_read_header,

100 .read_packet = ff_raw_read_partial_packet,

101 .flags= AVFMT_GENERIC_INDEX,

102 .extensions = "ac3",

103 .raw_codec_id = AV_CODEC_ID_AC3,

104 };

105 #endif

106

107 #if CONFIG_EAC3_DEMUXER

108 static int eac3_probe(AVProbeData *p)

109 {

110 return ac3_eac3_probe(p, AV_CODEC_ID_EAC3);

111 }

112

113 AVInputFormat ff_eac3_demuxer = {

114 .name = "eac3",

115 .long_name = NULL_IF_CONFIG_SMALL("raw E-AC-3"),

116 .read_probe = eac3_probe,

117 .read_header = ff_raw_audio_read_header,

118 .read_packet = ff_raw_read_partial_packet,

119 .flags = AVFMT_GENERIC_INDEX,

120 .extensions = "eac3",

121 .raw_codec_id = AV_CODEC_ID_EAC3,

122 };

123 #endif

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