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Diffstat (limited to '')
| -rw-r--r-- | media/ffvpx/libavcodec/mpegaudiodecheader.c | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/media/ffvpx/libavcodec/mpegaudiodecheader.c b/media/ffvpx/libavcodec/mpegaudiodecheader.c new file mode 100644 index 0000000000..ef63befbf4 --- /dev/null +++ b/media/ffvpx/libavcodec/mpegaudiodecheader.c @@ -0,0 +1,152 @@ +/* + * 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 + * MPEG Audio header decoder. + */ + +#include "libavutil/macros.h" + +#include "mpegaudio.h" +#include "mpegaudiodata.h" +#include "mpegaudiodecheader.h" + + +int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header) +{ + int sample_rate, frame_size, mpeg25, padding; + int sample_rate_index, bitrate_index; + int ret; + + ret = ff_mpa_check_header(header); + if (ret < 0) + return ret; + + 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; + if (sample_rate_index >= FF_ARRAY_ELEMS(ff_mpa_freq_tab)) + sample_rate_index = 0; + 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) + ff_dlog(NULL, "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) + ff_dlog(NULL, "ms-"); + if (s->mode_ext & MODE_EXT_I_STEREO) + ff_dlog(NULL, "i-"); + } + ff_dlog(NULL, "stereo"); + } else { + ff_dlog(NULL, "mono"); + } + ff_dlog(NULL, "\n"); +#endif + return 0; +} + +int ff_mpa_decode_header(uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate, enum AVCodecID *codec_id) +{ + MPADecodeHeader s1, *s = &s1; + + if (avpriv_mpegaudio_decode_header(s, head) != 0) { + return -1; + } + + switch(s->layer) { + case 1: + *codec_id = AV_CODEC_ID_MP1; + *frame_size = 384; + break; + case 2: + *codec_id = AV_CODEC_ID_MP2; + *frame_size = 1152; + break; + default: + case 3: + if (*codec_id != AV_CODEC_ID_MP3ADU) + *codec_id = AV_CODEC_ID_MP3; + if (s->lsf) + *frame_size = 576; + else + *frame_size = 1152; + break; + } + + *sample_rate = s->sample_rate; + *channels = s->nb_channels; + *bit_rate = s->bit_rate; + return s->frame_size; +} |