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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 6148 | serge | 1 | /* |
| 2 | * MPEG Audio header decoder |
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| 3 | * Copyright (c) 2001, 2002 Fabrice Bellard |
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| 4 | * |
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| 5 | * This file is part of FFmpeg. |
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| 6 | * |
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| 7 | * FFmpeg is free software; you can redistribute it and/or |
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| 8 | * modify it under the terms of the GNU Lesser General Public |
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| 9 | * License as published by the Free Software Foundation; either |
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| 10 | * version 2.1 of the License, or (at your option) any later version. |
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| 11 | * |
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| 12 | * FFmpeg is distributed in the hope that it will be useful, |
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| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 15 | * Lesser General Public License for more details. |
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| 16 | * |
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| 17 | * You should have received a copy of the GNU Lesser General Public |
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| 18 | * License along with FFmpeg; if not, write to the Free Software |
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| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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| 20 | */ |
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| 21 | |||
| 22 | /** |
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| 23 | * @file |
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| 24 | * MPEG Audio header decoder. |
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| 25 | */ |
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| 26 | |||
| 27 | #include "avcodec.h" |
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| 28 | #include "mpegaudio.h" |
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| 29 | #include "mpegaudiodata.h" |
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| 30 | #include "mpegaudiodecheader.h" |
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| 31 | |||
| 32 | |||
| 33 | int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header) |
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| 34 | { |
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| 35 | int sample_rate, frame_size, mpeg25, padding; |
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| 36 | int sample_rate_index, bitrate_index; |
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| 37 | if (header & (1<<20)) { |
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| 38 | s->lsf = (header & (1<<19)) ? 0 : 1; |
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| 39 | mpeg25 = 0; |
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| 40 | } else { |
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| 41 | s->lsf = 1; |
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| 42 | mpeg25 = 1; |
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| 43 | } |
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| 44 | |||
| 45 | s->layer = 4 - ((header >> 17) & 3); |
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| 46 | /* extract frequency */ |
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| 47 | sample_rate_index = (header >> 10) & 3; |
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| 48 | sample_rate = avpriv_mpa_freq_tab[sample_rate_index] >> (s->lsf + mpeg25); |
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| 49 | sample_rate_index += 3 * (s->lsf + mpeg25); |
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| 50 | s->sample_rate_index = sample_rate_index; |
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| 51 | s->error_protection = ((header >> 16) & 1) ^ 1; |
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| 52 | s->sample_rate = sample_rate; |
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| 53 | |||
| 54 | bitrate_index = (header >> 12) & 0xf; |
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| 55 | padding = (header >> 9) & 1; |
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| 56 | //extension = (header >> 8) & 1; |
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| 57 | s->mode = (header >> 6) & 3; |
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| 58 | s->mode_ext = (header >> 4) & 3; |
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| 59 | //copyright = (header >> 3) & 1; |
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| 60 | //original = (header >> 2) & 1; |
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| 61 | //emphasis = header & 3; |
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| 62 | |||
| 63 | if (s->mode == MPA_MONO) |
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| 64 | s->nb_channels = 1; |
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| 65 | else |
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| 66 | s->nb_channels = 2; |
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| 67 | |||
| 68 | if (bitrate_index != 0) { |
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| 69 | frame_size = avpriv_mpa_bitrate_tab[s->lsf][s->layer - 1][bitrate_index]; |
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| 70 | s->bit_rate = frame_size * 1000; |
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| 71 | switch(s->layer) { |
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| 72 | case 1: |
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| 73 | frame_size = (frame_size * 12000) / sample_rate; |
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| 74 | frame_size = (frame_size + padding) * 4; |
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| 75 | break; |
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| 76 | case 2: |
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| 77 | frame_size = (frame_size * 144000) / sample_rate; |
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| 78 | frame_size += padding; |
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| 79 | break; |
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| 80 | default: |
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| 81 | case 3: |
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| 82 | frame_size = (frame_size * 144000) / (sample_rate << s->lsf); |
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| 83 | frame_size += padding; |
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| 84 | break; |
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| 85 | } |
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| 86 | s->frame_size = frame_size; |
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| 87 | } else { |
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| 88 | /* if no frame size computed, signal it */ |
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| 89 | return 1; |
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| 90 | } |
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| 91 | |||
| 92 | #if defined(DEBUG) |
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| 93 | av_dlog(NULL, "layer%d, %d Hz, %d kbits/s, ", |
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| 94 | s->layer, s->sample_rate, s->bit_rate); |
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| 95 | if (s->nb_channels == 2) { |
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| 96 | if (s->layer == 3) { |
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| 97 | if (s->mode_ext & MODE_EXT_MS_STEREO) |
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| 98 | av_dlog(NULL, "ms-"); |
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| 99 | if (s->mode_ext & MODE_EXT_I_STEREO) |
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| 100 | av_dlog(NULL, "i-"); |
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| 101 | } |
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| 102 | av_dlog(NULL, "stereo"); |
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| 103 | } else { |
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| 104 | av_dlog(NULL, "mono"); |
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| 105 | } |
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| 106 | av_dlog(NULL, "\n"); |
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| 107 | #endif |
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| 108 | return 0; |
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| 109 | } |
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| 110 | |||
| 111 | int avpriv_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate) |
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| 112 | { |
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| 113 | MPADecodeHeader s1, *s = &s1; |
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| 114 | |||
| 115 | if (ff_mpa_check_header(head) != 0) |
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| 116 | return -1; |
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| 117 | |||
| 118 | if (avpriv_mpegaudio_decode_header(s, head) != 0) { |
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| 119 | return -1; |
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| 120 | } |
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| 121 | |||
| 122 | switch(s->layer) { |
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| 123 | case 1: |
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| 124 | avctx->codec_id = AV_CODEC_ID_MP1; |
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| 125 | *frame_size = 384; |
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| 126 | break; |
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| 127 | case 2: |
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| 128 | avctx->codec_id = AV_CODEC_ID_MP2; |
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| 129 | *frame_size = 1152; |
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| 130 | break; |
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| 131 | default: |
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| 132 | case 3: |
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| 133 | avctx->codec_id = AV_CODEC_ID_MP3; |
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| 134 | if (s->lsf) |
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| 135 | *frame_size = 576; |
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| 136 | else |
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| 137 | *frame_size = 1152; |
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| 138 | break; |
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| 139 | } |
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| 140 | |||
| 141 | *sample_rate = s->sample_rate; |
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| 142 | *channels = s->nb_channels; |
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| 143 | *bit_rate = s->bit_rate; |
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| 144 | return s->frame_size; |
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| 145 | } |