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4bd8e17c AJ |
1 | /* |
2 | * MPEG Audio header decoder | |
406792e7 | 3 | * Copyright (c) 2001, 2002 Fabrice Bellard |
4bd8e17c | 4 | * |
2912e87a | 5 | * This file is part of Libav. |
4bd8e17c | 6 | * |
2912e87a | 7 | * Libav is free software; you can redistribute it and/or |
4bd8e17c AJ |
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 | * | |
2912e87a | 12 | * Libav is distributed in the hope that it will be useful, |
4bd8e17c AJ |
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 | |
2912e87a | 18 | * License along with Libav; if not, write to the Free Software |
4bd8e17c AJ |
19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
20 | */ | |
21 | ||
22 | /** | |
ba87f080 | 23 | * @file |
4bd8e17c AJ |
24 | * MPEG Audio header decoder. |
25 | */ | |
26 | ||
4bd8e17c AJ |
27 | #include "avcodec.h" |
28 | #include "mpegaudio.h" | |
29 | #include "mpegaudiodata.h" | |
c6e1599b | 30 | #include "mpegaudiodecheader.h" |
4bd8e17c AJ |
31 | |
32 | ||
82ab61f9 | 33 | int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header) |
4bd8e17c AJ |
34 | { |
35 | int sample_rate, frame_size, mpeg25, padding; | |
36 | int sample_rate_index, bitrate_index; | |
37 | if (header & (1<<20)) { | |
38 | s->lsf = (header & (1<<19)) ? 0 : 1; | |
39 | mpeg25 = 0; | |
40 | } else { | |
41 | s->lsf = 1; | |
42 | mpeg25 = 1; | |
43 | } | |
44 | ||
45 | s->layer = 4 - ((header >> 17) & 3); | |
46 | /* extract frequency */ | |
47 | sample_rate_index = (header >> 10) & 3; | |
82ab61f9 | 48 | sample_rate = avpriv_mpa_freq_tab[sample_rate_index] >> (s->lsf + mpeg25); |
4bd8e17c AJ |
49 | sample_rate_index += 3 * (s->lsf + mpeg25); |
50 | s->sample_rate_index = sample_rate_index; | |
51 | s->error_protection = ((header >> 16) & 1) ^ 1; | |
52 | s->sample_rate = sample_rate; | |
53 | ||
54 | bitrate_index = (header >> 12) & 0xf; | |
55 | padding = (header >> 9) & 1; | |
56 | //extension = (header >> 8) & 1; | |
57 | s->mode = (header >> 6) & 3; | |
58 | s->mode_ext = (header >> 4) & 3; | |
59 | //copyright = (header >> 3) & 1; | |
60 | //original = (header >> 2) & 1; | |
61 | //emphasis = header & 3; | |
62 | ||
63 | if (s->mode == MPA_MONO) | |
64 | s->nb_channels = 1; | |
65 | else | |
66 | s->nb_channels = 2; | |
67 | ||
68 | if (bitrate_index != 0) { | |
82ab61f9 | 69 | frame_size = avpriv_mpa_bitrate_tab[s->lsf][s->layer - 1][bitrate_index]; |
4bd8e17c AJ |
70 | s->bit_rate = frame_size * 1000; |
71 | switch(s->layer) { | |
72 | case 1: | |
73 | frame_size = (frame_size * 12000) / sample_rate; | |
74 | frame_size = (frame_size + padding) * 4; | |
75 | break; | |
76 | case 2: | |
77 | frame_size = (frame_size * 144000) / sample_rate; | |
78 | frame_size += padding; | |
79 | break; | |
80 | default: | |
81 | case 3: | |
82 | frame_size = (frame_size * 144000) / (sample_rate << s->lsf); | |
83 | frame_size += padding; | |
84 | break; | |
85 | } | |
86 | s->frame_size = frame_size; | |
87 | } else { | |
88 | /* if no frame size computed, signal it */ | |
89 | return 1; | |
90 | } | |
91 | ||
92 | #if defined(DEBUG) | |
dfd2a005 | 93 | av_dlog(NULL, "layer%d, %d Hz, %d kbits/s, ", |
4bd8e17c AJ |
94 | s->layer, s->sample_rate, s->bit_rate); |
95 | if (s->nb_channels == 2) { | |
96 | if (s->layer == 3) { | |
97 | if (s->mode_ext & MODE_EXT_MS_STEREO) | |
dfd2a005 | 98 | av_dlog(NULL, "ms-"); |
4bd8e17c | 99 | if (s->mode_ext & MODE_EXT_I_STEREO) |
dfd2a005 | 100 | av_dlog(NULL, "i-"); |
4bd8e17c | 101 | } |
dfd2a005 | 102 | av_dlog(NULL, "stereo"); |
4bd8e17c | 103 | } else { |
dfd2a005 | 104 | av_dlog(NULL, "mono"); |
4bd8e17c | 105 | } |
dfd2a005 | 106 | av_dlog(NULL, "\n"); |
4bd8e17c AJ |
107 | #endif |
108 | return 0; | |
109 | } | |
0199e00b | 110 | |
82ab61f9 | 111 | int avpriv_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate) |
0199e00b MR |
112 | { |
113 | MPADecodeHeader s1, *s = &s1; | |
114 | ||
115 | if (ff_mpa_check_header(head) != 0) | |
116 | return -1; | |
117 | ||
82ab61f9 | 118 | if (avpriv_mpegaudio_decode_header(s, head) != 0) { |
0199e00b MR |
119 | return -1; |
120 | } | |
121 | ||
122 | switch(s->layer) { | |
123 | case 1: | |
36ef5369 | 124 | avctx->codec_id = AV_CODEC_ID_MP1; |
0199e00b MR |
125 | *frame_size = 384; |
126 | break; | |
127 | case 2: | |
36ef5369 | 128 | avctx->codec_id = AV_CODEC_ID_MP2; |
0199e00b MR |
129 | *frame_size = 1152; |
130 | break; | |
131 | default: | |
132 | case 3: | |
36ef5369 | 133 | avctx->codec_id = AV_CODEC_ID_MP3; |
0199e00b MR |
134 | if (s->lsf) |
135 | *frame_size = 576; | |
136 | else | |
137 | *frame_size = 1152; | |
138 | break; | |
139 | } | |
140 | ||
141 | *sample_rate = s->sample_rate; | |
142 | *channels = s->nb_channels; | |
143 | *bit_rate = s->bit_rate; | |
0199e00b MR |
144 | return s->frame_size; |
145 | } |