source: titan/libdreamdvd/a52_dec.c @ 14958

/* 
 * DreamDVD V0.9 - DVD-Player for Dreambox
 * Copyright (C) 2007 by Seddi
 * 
 * This DVD Player is based upon the great work from the libdvdnav project,
 * a52dec library, ffmpeg and the knowledge from all the people who made 
 * watching DVD within linux possible.
 * 
 * DreamDVD 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 of the License, or
 * (at your option) any later version.
 * 
 * DreamDVD 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 this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA
 *
 * part of libdreamdvd
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <errno.h>
#include <getopt.h>
#include <math.h>
#include <inttypes.h>
#include <dlfcn.h>


#include "a52dec.h"


// try to dynamically load and wrap liba52.so.0

int ddvd_load_liba52()
{
        a52_handle = dlopen("liba52.so.0",RTLD_LAZY);
        
        if (a52_handle)
        {
                a52_init = (a52_state_t* (*)(uint32_t)) dlsym(a52_handle, "a52_init");
                a52_samples = (sample_t* (*)(a52_state_t*)) dlsym(a52_handle, "a52_samples");
                a52_syncinfo = (int (*)(uint8_t*, int*, int*, int*)) dlsym(a52_handle, "a52_syncinfo");
                a52_frame = (int (*)(a52_state_t* ,uint8_t* ,int* ,level_t* ,sample_t)) dlsym(a52_handle, "a52_frame");
                a52_block = (int (*)(a52_state_t*)) dlsym(a52_handle, "a52_block");
                a52_free = (void (*)(a52_state_t*)) dlsym(a52_handle, "a52_free");

                printf("libdreamdvd: soft ac3 decoding is available, liba52.so.0 loaded !\n");
                return 1;
        }
        else
        {
                printf("libdreamdvd: soft ac3 decoding is not available, liba52.so.0 not found !\n");
                return 0;
        }
}

// close dynamically loaded liba52.so.0

void ddvd_close_liba52()
{
        dlclose(a52_handle);
}

// convert 32bit samples to 16bit

static inline int16_t a52_convert (int32_t i)
{
    i >>= 15;
    return (i > 32767) ? 32767 : ((i < -32768) ? -32768 : i);
}

// liba52 gives us 256 samples left - 256 samples right
// we need 1 left - 1 right so lets sort them

static void a52_convert2s16_2 (sample_t * _f, int16_t * s16)
{
    int i;
    int32_t * f = (int32_t *) _f;

    for (i = 0; i < 256; i++) {
        s16[2*i] = a52_convert (f[i]);
        s16[2*i+1] = a52_convert (f[i+256]);
    }
}

// a52 decode function (needs liba52)

int ddvd_ac3_decode(const uint8_t *input, unsigned int len, int16_t *output)
{
        static int sample_rate;
    static int flags;
    int bit_rate;
        int out_len=0;
        const uint8_t *end; 
        end=input+len;
        
    static uint8_t buf[3840];
    static uint8_t * bufptr = buf;
    static uint8_t * bufpos = buf + 7;

    while (1) {
        len = end - input;
        if (!len)
            break;
        if (len > bufpos - bufptr)
            len = bufpos - bufptr;
        
        memcpy (bufptr, input, len);
        bufptr += len;
        input += len;

        if (bufptr == bufpos) {
            if (bufpos == buf + 7) {
                int length;

                length = a52_syncinfo (buf, &flags, &sample_rate, &bit_rate);
                if (!length) {
                    for (bufptr = buf; bufptr < buf + 6; bufptr++)
                        bufptr[0] = bufptr[1];
                    continue;
                }
                bufpos = buf + length;
            } else {
                level_t level;
                sample_t bias;
                int i;

                flags=A52_DOLBY|A52_ADJUST_LEVEL;
                        
                bias=0;
                level=(1 << 26);

                if (a52_frame (state, buf, &flags, &level, bias))
                    goto error;

                for (i = 0; i < 6; i++) {
                    if (a52_block (state))
                        goto error;
                        a52_convert2s16_2(a52_samples(state),output);
                        output+=512;
                        out_len+=1024;
                }
                bufptr = buf;
                bufpos = buf + 7;
                continue;
            error:
                bufptr = buf;
                bufpos = buf + 7;
            }
        }
    }
        return out_len;
}