/* 
 *    decode.c
 *
 *	Copyright (C) Aaron Holtzman - May 1999
 *
 *  This file is part of ac3dec, a free Dolby AC-3 stream decoder.
 *	
 *  ac3dec is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *   
 *  ac3dec 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 General Public License for more details.
 *   
 *  You should have received a copy of the GNU General Public License
 *  along with GNU Make; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
 *
 *
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif 

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/time.h>


#include "ac3.h"
#include "ac3_internal.h"
#include "bitstream.h"
#include "downmix.h"
#include "imdct.h"
#include "exponent.h"
#include "coeff.h"
#include "bit_allocate.h"
#include "parse.h"
#include "crc.h"
#include "stats.h"
#include "rematrix.h"
#include "sanity_check.h"
#include "debug.h"

//our global config structure
ac3_config_t ac3_config;
uint32_t error_flag = 0;

static audblk_t audblk;
static bsi_t bsi;
static syncinfo_t syncinfo;
static uint32_t frame_count = 0;
static uint32_t done_banner;

//the floating point samples for one audblk
static stream_samples_t samples;

//the integer samples for the entire frame (with enough space for 2 ch out)
//if this size change, be sure to change the size when muting
static int16_t s16_samples[2 * 6 * 256] __attribute__ ((aligned(16)));

// downmix stuff
static float cmixlev_lut[4] = { 0.707, 0.595, 0.500, 0.707 };
static float smixlev_lut[4] = { 0.707, 0.500, 0.0   , 0.500 };
static dm_par_t dm_par;
 
//Storage for the syncframe
#define BUFFER_MAX_SIZE 4096
static uint8_t buffer[BUFFER_MAX_SIZE];
static uint32_t buffer_size = 0;;

static uint8_t *buffpos_cur = NULL;
static uint8_t *buffpos_end = NULL;

static int fill_buffer(){
    ac3_config.fill_buffer_callback(&buffpos_cur,&buffpos_end);
    if(buffpos_cur>=buffpos_end) return 0;
    return 1;
}

void ac3_bitstream_reset(){
    buffpos_cur=buffpos_end=NULL;
}

uint32_t
decode_buffer_syncframe(syncinfo_t *syncinfo)
{
	uint16_t syncword = 0xFFFF;
    
        buffer_size=0;

	// 
	// Find an ac3 sync frame.
	// 
	while (syncword != 0x0b77) {
		if(buffpos_cur >= buffpos_end)
                    if(!fill_buffer()) return 0;
		syncword = (syncword << 8) + *buffpos_cur++;
	}

	//need the next 3 bytes to decide how big the frame is
	while (buffer_size < 3) {
		if(buffpos_cur >= buffpos_end)
                    if(!fill_buffer()) return 0;

		buffer[buffer_size++] = *buffpos_cur++;
	}
	
	parse_syncinfo(syncinfo,buffer);
//	stats_print_syncinfo(syncinfo);

	while (buffer_size < syncinfo->frame_size * 2 - 2) {
		if(buffpos_cur >= buffpos_end)
                    if(!fill_buffer()) return 0;
		buffer[buffer_size++] = *buffpos_cur++;
	}

	// Check the crc over the entire frame 
	crc_init();
	crc_process_frame(buffer,syncinfo->frame_size * 2 - 2);

	if (!crc_validate()) {
		error_flag = 1;
		fprintf(stderr,"** CRC failed - skipping frame **\n");
		return 0;
	}

	//
	//if we got to this point, we found a valid ac3 frame to decode
	//

	bitstream_init (buffer);
	//get rid of the syncinfo struct as we already parsed it
	bitstream_get (24);
        
        return 1;
}

void
decode_mute(void)
{
	//mute the frame
	memset (s16_samples, 0, sizeof(int16_t) * 256 * 2 * 6);
	error_flag = 0;
}


void
ac3_init(void)
{
	imdct_init();
	sanity_check_init(&syncinfo,&bsi,&audblk);
	decode_mute();
}

ac3_frame_t ac3_frame;

ac3_frame_t*
ac3_decode_frame()
{
	uint32_t i;

	if(!decode_buffer_syncframe(&syncinfo)) return NULL;
        
//		dprintf("(decode) begin frame %d\n",frame_count++);

		if(error_flag)
			decode_mute();

		parse_bsi(&bsi);

		if(!done_banner) {
			stats_print_banner(&syncinfo,&bsi);
			done_banner = 1;
		}

		// compute downmix parameters
		// downmix to tow channels for now
		dm_par.clev = 0.0; dm_par.slev = 0.0; dm_par.unit = 1.0;
		if (bsi.acmod & 0x1)	// have center
			dm_par.clev = cmixlev_lut[bsi.cmixlev];

		if (bsi.acmod & 0x4)	// have surround channels
			dm_par.slev = smixlev_lut[bsi.surmixlev];

		dm_par.unit /= 1.0 + dm_par.clev + dm_par.slev;
		dm_par.clev *= dm_par.unit;
		dm_par.slev *= dm_par.unit;

		for(i=0; i < 6; i++) {
			//Initialize freq/time sample storage
			memset (samples, 0, sizeof(float) * 256 * (bsi.nfchans + bsi.lfeon));

			// Extract most of the audblk info from the bitstream
			// (minus the mantissas 
			parse_audblk(&bsi,&audblk);

			// Take the differential exponent data and turn it into
			// absolute exponents 
			exponent_unpack(&bsi,&audblk); 
			if(error_flag) return NULL;

			// Figure out how many bits per mantissa 
			bit_allocate(syncinfo.fscod,&bsi,&audblk);

			// Extract the mantissas from the stream and
			// generate floating point frequency coefficients
			coeff_unpack (&bsi,&audblk,samples);
			if(error_flag) return NULL;

			if(bsi.acmod == 0x2)
				rematrix (&audblk,samples);

			// Convert the frequency samples into time samples 
			imdct (&bsi,&audblk,samples, &s16_samples[i * 2 * 256], &dm_par);

			// Downmix into the requested number of channels
			// and convert floating point to int16_t
			// downmix(&bsi,samples,&s16_samples[i * 2 * 256]);

			sanity_check(&syncinfo,&bsi,&audblk);
			if(error_flag) return NULL;

			continue;
		}

                ac3_frame.sampling_rate=syncinfo.sampling_rate;
                ac3_frame.audio_data=s16_samples;

//		ao_functions->play(s16_samples, 256 * 6 * 2);

	return &ac3_frame;
}