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https://github.com/alsa-project/alsa-tools.git
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150 lines
3.5 KiB
C
150 lines
3.5 KiB
C
/*
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* decode.c
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*
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* Copyright (C) Aaron Holtzman - May 1999
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*
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* This file is part of ac3dec, a free Dolby AC-3 stream decoder.
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*
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* ac3dec is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* ac3dec 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
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNU Make; see the file COPYING. If not, write to
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* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <stdlib.h>
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#include <stdio.h>
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#include <errno.h>
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#include <string.h>
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#include <sys/time.h>
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#include "ac3.h"
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#include "ac3_internal.h"
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#include "bitstream.h"
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#include "imdct.h"
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#include "exponent.h"
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#include "coeff.h"
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#include "bit_allocate.h"
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#include "parse.h"
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#include "crc.h"
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#include "stats.h"
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#include "rematrix.h"
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#include "sanity_check.h"
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#include "downmix.h"
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#include "debug.h"
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//our global config structure
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ac3_config_t ac3_config;
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uint_32 error_flag = 0;
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static audblk_t audblk;
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static bsi_t bsi;
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static syncinfo_t syncinfo;
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static uint_32 frame_count = 0;
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static uint_32 done_banner;
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static ac3_frame_t frame;
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//the floating point samples for one audblk
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static stream_samples_t samples;
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//the integer samples for the entire frame (with enough space for 2 ch out)
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//if this size change, be sure to change the size when muting
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static sint_16 s16_samples[6 * 6 * 256];
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void
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ac3_init(ac3_config_t *config)
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{
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memcpy(&ac3_config,config,sizeof(ac3_config_t));
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bitstream_init(config->fill_buffer_callback);
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imdct_init();
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sanity_check_init(&syncinfo,&bsi,&audblk);
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frame.audio_data = s16_samples;
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}
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ac3_frame_t*
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ac3_decode_frame(void)
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{
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uint_32 i;
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//find a syncframe and parse
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if (parse_syncinfo(&syncinfo) < 0)
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return NULL;
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if(error_flag)
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goto error;
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dprintf("(decode) begin frame %d\n",frame_count++);
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frame.sampling_rate = syncinfo.sampling_rate;
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parse_bsi(&bsi);
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if(!done_banner && !(ac3_config.flags & AC3_QUIET))
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{
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stats_print_banner(&syncinfo,&bsi);
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done_banner = 1;
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}
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for(i=0; i < 6; i++)
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{
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//Initialize freq/time sample storage
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memset(samples,0,sizeof(float) * 256 * (bsi.nfchans + bsi.lfeon));
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// Extract most of the audblk info from the bitstream
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// (minus the mantissas
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parse_audblk(&bsi,&audblk);
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// Take the differential exponent data and turn it into
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// absolute exponents
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exponent_unpack(&bsi,&audblk);
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if(error_flag)
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goto error;
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// Figure out how many bits per mantissa
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bit_allocate(syncinfo.fscod,&bsi,&audblk);
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// Extract the mantissas from the stream and
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// generate floating point frequency coefficients
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coeff_unpack(&bsi,&audblk,samples);
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if(error_flag)
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goto error;
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if(bsi.acmod == 0x2)
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rematrix(&audblk,samples);
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// Convert the frequency samples into time samples
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imdct(&bsi,&audblk,samples);
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// Downmix into the requested number of channels
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// and convert floating point to sint_16
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downmix(&bsi,samples,&s16_samples[i * ac3_config.num_output_ch * 256]);
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sanity_check(&syncinfo,&bsi,&audblk);
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if(error_flag)
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goto error;
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}
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parse_auxdata(&syncinfo);
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return &frame;
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error:
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//mute the frame
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memset(s16_samples,0,sizeof(sint_16) * 256 * 2 * 6);
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error_flag = 0;
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return &frame;
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}
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