mirror of https://github.com/FFmpeg/FFmpeg.git
Originally committed as revision 9080 to svn://svn.ffmpeg.org/ffmpeg/trunkpull/126/head
Aurelien Jacobs
18 years ago
parent
663deb54af
commit
4bd8e17c8d
7 changed files with 234 additions and 155 deletions
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/*
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* MPEG Audio header decoder |
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* Copyright (c) 2001, 2002 Fabrice Bellard. |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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/**
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* @file mpegaudiodecheader.c |
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* MPEG Audio header decoder. |
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*/ |
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//#define DEBUG
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#include "avcodec.h" |
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#include "mpegaudio.h" |
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#include "mpegaudiodata.h" |
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int decode_header(MPADecodeContext *s, uint32_t header) |
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{ |
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int sample_rate, frame_size, mpeg25, padding; |
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int sample_rate_index, bitrate_index; |
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if (header & (1<<20)) { |
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s->lsf = (header & (1<<19)) ? 0 : 1; |
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mpeg25 = 0; |
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} else { |
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s->lsf = 1; |
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mpeg25 = 1; |
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} |
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s->layer = 4 - ((header >> 17) & 3); |
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/* extract frequency */ |
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sample_rate_index = (header >> 10) & 3; |
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sample_rate = ff_mpa_freq_tab[sample_rate_index] >> (s->lsf + mpeg25); |
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sample_rate_index += 3 * (s->lsf + mpeg25); |
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s->sample_rate_index = sample_rate_index; |
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s->error_protection = ((header >> 16) & 1) ^ 1; |
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s->sample_rate = sample_rate; |
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bitrate_index = (header >> 12) & 0xf; |
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padding = (header >> 9) & 1; |
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//extension = (header >> 8) & 1;
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s->mode = (header >> 6) & 3; |
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s->mode_ext = (header >> 4) & 3; |
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//copyright = (header >> 3) & 1;
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//original = (header >> 2) & 1;
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//emphasis = header & 3;
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if (s->mode == MPA_MONO) |
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s->nb_channels = 1; |
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else |
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s->nb_channels = 2; |
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if (bitrate_index != 0) { |
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frame_size = ff_mpa_bitrate_tab[s->lsf][s->layer - 1][bitrate_index]; |
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s->bit_rate = frame_size * 1000; |
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switch(s->layer) { |
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case 1: |
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frame_size = (frame_size * 12000) / sample_rate; |
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frame_size = (frame_size + padding) * 4; |
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break; |
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case 2: |
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frame_size = (frame_size * 144000) / sample_rate; |
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frame_size += padding; |
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break; |
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default: |
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case 3: |
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frame_size = (frame_size * 144000) / (sample_rate << s->lsf); |
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frame_size += padding; |
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break; |
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} |
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s->frame_size = frame_size; |
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} else { |
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/* if no frame size computed, signal it */ |
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return 1; |
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} |
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#if defined(DEBUG) |
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dprintf(s->avctx, "layer%d, %d Hz, %d kbits/s, ", |
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s->layer, s->sample_rate, s->bit_rate); |
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if (s->nb_channels == 2) { |
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if (s->layer == 3) { |
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if (s->mode_ext & MODE_EXT_MS_STEREO) |
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dprintf(s->avctx, "ms-"); |
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if (s->mode_ext & MODE_EXT_I_STEREO) |
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dprintf(s->avctx, "i-"); |
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} |
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dprintf(s->avctx, "stereo"); |
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} else { |
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dprintf(s->avctx, "mono"); |
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} |
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dprintf(s->avctx, "\n"); |
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#endif |
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return 0; |
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} |
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@ -0,0 +1,39 @@ |
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/*
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* MPEG Audio header decoder |
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* Copyright (c) 2001, 2002 Fabrice Bellard. |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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/**
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* @file mpegaudiodecheader.c |
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* MPEG Audio header decoder. |
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*/ |
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#ifndef MPEGAUDIODECHEADER_H |
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#define MPEGAUDIODECHEADER_H |
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#include "common.h" |
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#include "mpegaudio.h" |
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/* header decoding. MUST check the header before because no
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consistency check is done there. Return 1 if free format found and |
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that the frame size must be computed externally */ |
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int decode_header(MPADecodeContext *s, uint32_t header); |
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#endif /* MPEGAUDIODECHEADER_H */ |
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