From 4bd8e17c8d371dc05af63b15c11342e40184df61 Mon Sep 17 00:00:00 2001 From: Aurelien Jacobs Date: Sun, 20 May 2007 13:40:07 +0000 Subject: loosen dependencies over mpegaudiodec Originally committed as revision 9080 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavcodec/mpegaudiodecheader.c | 109 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 109 insertions(+) create mode 100644 libavcodec/mpegaudiodecheader.c (limited to 'libavcodec/mpegaudiodecheader.c') diff --git a/libavcodec/mpegaudiodecheader.c b/libavcodec/mpegaudiodecheader.c new file mode 100644 index 0000000000..0b75e82e65 --- /dev/null +++ b/libavcodec/mpegaudiodecheader.c @@ -0,0 +1,109 @@ +/* + * MPEG Audio header decoder + * Copyright (c) 2001, 2002 Fabrice Bellard. + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +/** + * @file mpegaudiodecheader.c + * MPEG Audio header decoder. + */ + +//#define DEBUG +#include "avcodec.h" +#include "mpegaudio.h" +#include "mpegaudiodata.h" + + +int decode_header(MPADecodeContext *s, uint32_t header) +{ + int sample_rate, frame_size, mpeg25, padding; + int sample_rate_index, bitrate_index; + if (header & (1<<20)) { + s->lsf = (header & (1<<19)) ? 0 : 1; + mpeg25 = 0; + } else { + s->lsf = 1; + mpeg25 = 1; + } + + s->layer = 4 - ((header >> 17) & 3); + /* extract frequency */ + sample_rate_index = (header >> 10) & 3; + sample_rate = ff_mpa_freq_tab[sample_rate_index] >> (s->lsf + mpeg25); + sample_rate_index += 3 * (s->lsf + mpeg25); + s->sample_rate_index = sample_rate_index; + s->error_protection = ((header >> 16) & 1) ^ 1; + s->sample_rate = sample_rate; + + bitrate_index = (header >> 12) & 0xf; + padding = (header >> 9) & 1; + //extension = (header >> 8) & 1; + s->mode = (header >> 6) & 3; + s->mode_ext = (header >> 4) & 3; + //copyright = (header >> 3) & 1; + //original = (header >> 2) & 1; + //emphasis = header & 3; + + if (s->mode == MPA_MONO) + s->nb_channels = 1; + else + s->nb_channels = 2; + + if (bitrate_index != 0) { + frame_size = ff_mpa_bitrate_tab[s->lsf][s->layer - 1][bitrate_index]; + s->bit_rate = frame_size * 1000; + switch(s->layer) { + case 1: + frame_size = (frame_size * 12000) / sample_rate; + frame_size = (frame_size + padding) * 4; + break; + case 2: + frame_size = (frame_size * 144000) / sample_rate; + frame_size += padding; + break; + default: + case 3: + frame_size = (frame_size * 144000) / (sample_rate << s->lsf); + frame_size += padding; + break; + } + s->frame_size = frame_size; + } else { + /* if no frame size computed, signal it */ + return 1; + } + +#if defined(DEBUG) + dprintf(s->avctx, "layer%d, %d Hz, %d kbits/s, ", + s->layer, s->sample_rate, s->bit_rate); + if (s->nb_channels == 2) { + if (s->layer == 3) { + if (s->mode_ext & MODE_EXT_MS_STEREO) + dprintf(s->avctx, "ms-"); + if (s->mode_ext & MODE_EXT_I_STEREO) + dprintf(s->avctx, "i-"); + } + dprintf(s->avctx, "stereo"); + } else { + dprintf(s->avctx, "mono"); + } + dprintf(s->avctx, "\n"); +#endif + return 0; +} -- cgit v1.2.3