mirror of https://git.ffmpeg.org/ffmpeg.git
166 lines
4.6 KiB
C
166 lines
4.6 KiB
C
/*
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* AC3 parser
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* Copyright (c) 2003 Fabrice Bellard.
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* Copyright (c) 2003 Michael Niedermayer.
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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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#include "parser.h"
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#include "ac3_parser.h"
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#include "aac_ac3_parser.h"
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#include "bitstream.h"
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#define AC3_HEADER_SIZE 7
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static const uint8_t eac3_blocks[4] = {
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1, 2, 3, 6
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};
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int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
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{
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GetBitContext gbc;
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memset(hdr, 0, sizeof(*hdr));
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init_get_bits(&gbc, buf, 54);
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hdr->sync_word = get_bits(&gbc, 16);
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if(hdr->sync_word != 0x0B77)
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return AC3_PARSE_ERROR_SYNC;
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/* read ahead to bsid to make sure this is AC-3, not E-AC-3 */
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hdr->bsid = show_bits_long(&gbc, 29) & 0x1F;
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if(hdr->bsid > 10)
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return AC3_PARSE_ERROR_BSID;
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hdr->crc1 = get_bits(&gbc, 16);
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hdr->sr_code = get_bits(&gbc, 2);
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if(hdr->sr_code == 3)
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return AC3_PARSE_ERROR_SAMPLE_RATE;
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hdr->frmsizecod = get_bits(&gbc, 6);
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if(hdr->frmsizecod > 37)
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return AC3_PARSE_ERROR_FRAME_SIZE;
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skip_bits(&gbc, 5); // skip bsid, already got it
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hdr->bsmod = get_bits(&gbc, 3);
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hdr->acmod = get_bits(&gbc, 3);
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if((hdr->acmod & 1) && hdr->acmod != AC3_ACMOD_MONO) {
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hdr->cmixlev = get_bits(&gbc, 2);
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}
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if(hdr->acmod & 4) {
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hdr->surmixlev = get_bits(&gbc, 2);
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}
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if(hdr->acmod == AC3_ACMOD_STEREO) {
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hdr->dsurmod = get_bits(&gbc, 2);
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}
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hdr->lfeon = get_bits1(&gbc);
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hdr->sr_shift = FFMAX(hdr->bsid, 8) - 8;
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hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
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hdr->bit_rate = (ff_ac3_bitrate_tab[hdr->frmsizecod>>1] * 1000) >> hdr->sr_shift;
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hdr->channels = ff_ac3_channels_tab[hdr->acmod] + hdr->lfeon;
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hdr->frame_size = ff_ac3_frame_size_tab[hdr->frmsizecod][hdr->sr_code] * 2;
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return 0;
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}
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static int ac3_sync(const uint8_t *buf, int *channels, int *sample_rate,
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int *bit_rate, int *samples)
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{
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int err;
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unsigned int sr_code, acmod, bsid, lfeon;
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unsigned int strmtyp, substreamid, frmsiz, sr_code2, numblkscod;
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GetBitContext bits;
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AC3HeaderInfo hdr;
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err = ff_ac3_parse_header(buf, &hdr);
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if(err < 0 && err != -2)
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return 0;
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bsid = hdr.bsid;
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if(bsid <= 10) { /* Normal AC-3 */
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*sample_rate = hdr.sample_rate;
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*bit_rate = hdr.bit_rate;
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*channels = hdr.channels;
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*samples = AC3_FRAME_SIZE;
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return hdr.frame_size;
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} else if (bsid > 10 && bsid <= 16) { /* Enhanced AC-3 */
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init_get_bits(&bits, &buf[2], (AC3_HEADER_SIZE-2) * 8);
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strmtyp = get_bits(&bits, 2);
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substreamid = get_bits(&bits, 3);
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if (strmtyp != 0 || substreamid != 0)
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return 0; /* Currently don't support additional streams */
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frmsiz = get_bits(&bits, 11) + 1;
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if(frmsiz*2 < AC3_HEADER_SIZE)
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return 0;
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sr_code = get_bits(&bits, 2);
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if (sr_code == 3) {
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sr_code2 = get_bits(&bits, 2);
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numblkscod = 3;
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if(sr_code2 == 3)
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return 0;
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*sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
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} else {
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numblkscod = get_bits(&bits, 2);
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*sample_rate = ff_ac3_sample_rate_tab[sr_code];
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}
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acmod = get_bits(&bits, 3);
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lfeon = get_bits1(&bits);
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*samples = eac3_blocks[numblkscod] * 256;
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*bit_rate = frmsiz * (*sample_rate) * 16 / (*samples);
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*channels = ff_ac3_channels_tab[acmod] + lfeon;
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return frmsiz * 2;
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}
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/* Unsupported bitstream version */
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return 0;
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}
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static int ac3_parse_init(AVCodecParserContext *s1)
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{
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AACAC3ParseContext *s = s1->priv_data;
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s->inbuf_ptr = s->inbuf;
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s->header_size = AC3_HEADER_SIZE;
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s->sync = ac3_sync;
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return 0;
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}
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AVCodecParser ac3_parser = {
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{ CODEC_ID_AC3 },
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sizeof(AACAC3ParseContext),
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ac3_parse_init,
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ff_aac_ac3_parse,
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NULL,
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};
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