rockbox/apps/codecs/demac/libdemac/decoder.c

/*

libdemac - A Monkey's Audio decoder

$Id$

Copyright (C) Dave Chapman 2007

This program 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.

This program 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., 51 Franklin St, Fifth Floor, Boston, MA 02110, USA

*/

#include <inttypes.h>
#include <string.h>

#include "demac.h"
#include "predictor.h"
#include "entropy.h"
#include "filter.h"

/* Statically allocate the filter buffers */

static int16_t filterbuf32[(32*3 + HISTORY_SIZE) * 2]     /* 4480 bytes */
               IBSS_ATTR __attribute__((aligned(16)));
static int16_t filterbuf256[(256*3 + HISTORY_SIZE) * 2]   /* 5120 bytes */
               IBSS_ATTR __attribute__((aligned(16)));

/* This is only needed for "insane" files, and no Rockbox targets can
   hope to decode them in realtime anyway. */
static int16_t filterbuf1280[(1280*3 + HISTORY_SIZE) * 2] /* 17408 bytes */
               __attribute__((aligned(16)));

void init_frame_decoder(struct ape_ctx_t* ape_ctx,
                        unsigned char* inbuffer, int* firstbyte,
                        int* bytesconsumed)
{
    init_entropy_decoder(ape_ctx, inbuffer, firstbyte, bytesconsumed);
    //printf("CRC=0x%08x\n",ape_ctx->CRC);
    //printf("Flags=0x%08x\n",ape_ctx->frameflags);

    init_predictor_decoder(&ape_ctx->predictor);

    switch (ape_ctx->compressiontype)
    {
        case 2000:
            init_filter_16_11(filterbuf32);
            break;

        case 3000:
            init_filter_64_11(filterbuf256);
            break;

        case 4000:
            init_filter_256_13(filterbuf256);
            init_filter_32_10(filterbuf32);
            break;

        case 5000:
            init_filter_1280_15(filterbuf1280);
            init_filter_256_13(filterbuf256);
            init_filter_16_11(filterbuf32);
    }
}

int decode_chunk(struct ape_ctx_t* ape_ctx,
                 unsigned char* inbuffer, int* firstbyte,
                 int* bytesconsumed,
                 int32_t* decoded0, int32_t* decoded1, 
                 int count)
{
    int res;
    int32_t left, right;
#ifdef ROCKBOX
    int scale = (APE_OUTPUT_DEPTH - ape_ctx->bps);
    #define SCALE(x) ((x) << scale)
#else
    #define SCALE(x) (x)
#endif

    if ((ape_ctx->channels==1) || (ape_ctx->frameflags & APE_FRAMECODE_PSEUDO_STEREO)) {
        if (ape_ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
            res = entropy_decode(ape_ctx, inbuffer, firstbyte, bytesconsumed, decoded0, decoded1, count);
            /* We are pure silence, so we're done. */
            return 0;
        } else {
            res = entropy_decode(ape_ctx, inbuffer, firstbyte, bytesconsumed, decoded0, NULL, count);
        }
    
        switch (ape_ctx->compressiontype)
        {
            case 2000:
                apply_filter_16_11(ape_ctx->fileversion,decoded0,NULL,count);
                break;
    
            case 3000:
                apply_filter_64_11(ape_ctx->fileversion,decoded0,NULL,count);
                break;
    
            case 4000:
                apply_filter_32_10(ape_ctx->fileversion,decoded0,NULL,count);
                apply_filter_256_13(ape_ctx->fileversion,decoded0,NULL,count);
                break;
    
            case 5000:
                apply_filter_16_11(ape_ctx->fileversion,decoded0,NULL,count);
                apply_filter_256_13(ape_ctx->fileversion,decoded0,NULL,count);
                apply_filter_1280_15(ape_ctx->fileversion,decoded0,NULL,count);
        }

        /* Now apply the predictor decoding */
        predictor_decode_mono(&ape_ctx->predictor,decoded0,count);

        if (ape_ctx->channels==2) {
            /* Pseudo-stereo - just copy left channel to right channel */
            while (count--)
            {
                left = *decoded0;
                *(decoded1++) = *(decoded0++) = SCALE(left);
            }
        } else {
            /* Mono - do nothing unless it's 8-bit audio */
            if (ape_ctx->bps == 8) {
                /* TODO: Handle 8-bit streams */
            }
        }
    } else { /* Stereo */
        if (ape_ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
            /* We are pure silence, so we're done. */
            return 0;
        }
    
        res = entropy_decode(ape_ctx, inbuffer, firstbyte, bytesconsumed, decoded0, decoded1, count);

        /* Apply filters - compression type 1000 doesn't have any */
        switch (ape_ctx->compressiontype)
        {
            case 2000:
                apply_filter_16_11(ape_ctx->fileversion,decoded0,decoded1,count);
                break;
    
            case 3000:
                apply_filter_64_11(ape_ctx->fileversion,decoded0,decoded1,count);
                break;
    
            case 4000:
                apply_filter_32_10(ape_ctx->fileversion,decoded0,decoded1,count);
                apply_filter_256_13(ape_ctx->fileversion,decoded0,decoded1,count);
                break;
    
            case 5000:
                apply_filter_16_11(ape_ctx->fileversion,decoded0,decoded1,count);
                apply_filter_256_13(ape_ctx->fileversion,decoded0,decoded1,count);
                apply_filter_1280_15(ape_ctx->fileversion,decoded0,decoded1,count);
        }

        /* Now apply the predictor decoding */
        predictor_decode_stereo(&ape_ctx->predictor,decoded0,decoded1,count);

        if (ape_ctx->bps == 8) {
            /* TODO: Handle 8-bit streams */
        } else {
            /* Decorrelate and scale to output depth */
            while (count--)
            {
                left = *decoded1 - (*decoded0 / 2);
                right = left + *decoded0;

                *(decoded0++) = SCALE(left);
                *(decoded1++) = SCALE(right);
            }
        }
    }

    return res;
}