adpcm.c

Trolltech公司发布的图形界面操作系统。可在qt-embedded-2.3.7平台上编译为嵌入式图形界面操作系统。

/*
 * ADPCM codecs
 * Copyright (c) 2001 Fabrice Bellard.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include "avcodec.h"

/*
 * First version by Francois Revol [e-mail]
 *
 * Features and limitations:
 *
 * Reference documents:
 * http://www.pcisys.net/~melanson/codecs/adpcm.txt
 * http://www.geocities.com/SiliconValley/8682/aud3.txt
 * http://openquicktime.sourceforge.net/plugins.htm
 * XAnim sources (xa_codec.c) http://www.rasnaimaging.com/people/lapus/download.html
 * http://www.cs.ucla.edu/~leec/mediabench/applications.html
 * SoX source code http://home.sprynet.com/~cbagwell/sox.html
 */

#define BLKSIZE 1024

#define CLAMP_TO_SHORT(value) \
if (value > 32767) \
    value = 32767; \
else if (value < -32768) \
    value = -32768; \

/* step_table[] and index_table[] are from the ADPCM reference source */
/* This is the index table: */
static int index_table[16] = {
    -1, -1, -1, -1, 2, 4, 6, 8,
    -1, -1, -1, -1, 2, 4, 6, 8,
};

/* This is the step table. Note that many programs use slight deviations from
 * this table, but such deviations are negligible:
 */
static int step_table[89] = {
    7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
    19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
    50, 55, 60, 66, 73, 80, 88, 97, 107, 118,
    130, 143, 157, 173, 190, 209, 230, 253, 279, 307,
    337, 371, 408, 449, 494, 544, 598, 658, 724, 796,
    876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
    2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
    5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
    15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767
};

/* Those are for MS-ADPCM */
/* AdaptationTable[], AdaptCoeff1[], and AdaptCoeff2[] are from libsndfile */
static int AdaptationTable[] = {
        230, 230, 230, 230, 307, 409, 512, 614,
        768, 614, 512, 409, 307, 230, 230, 230
};

static int AdaptCoeff1[] = {
        256, 512, 0, 192, 240, 460, 392
};

static int AdaptCoeff2[] = {
        0, -256, 0, 64, 0, -208, -232
};

/* end of tables */

typedef struct ADPCMChannelStatus {
    int predictor;
    short int step_index;
    int step;
    /* for encoding */
    int prev_sample;

    /* MS version */
    short sample1;
    short sample2;
    int coeff1;
    int coeff2;
    int idelta;
} ADPCMChannelStatus;

typedef struct ADPCMContext {
    int channel; /* for stereo MOVs, decode left, then decode right, then tell it's decoded */
    ADPCMChannelStatus status[2];
    short sample_buffer[32]; /* hold left samples while waiting for right samples */
} ADPCMContext;

/* XXX: implement encoding */

static int adpcm_encode_init(AVCodecContext *avctx)
{
    if (avctx->channels > 2)
        return -1; /* only stereo or mono =) */
    switch(avctx->codec->id) {
    case CODEC_ID_ADPCM_IMA_QT:
        fprintf(stderr, "ADPCM: codec admcp_ima_qt unsupported for encoding !\n");
        avctx->frame_size = 64; /* XXX: can multiple of avctx->channels * 64 (left and right blocks are interleaved) */
        return -1;
        break;
    case CODEC_ID_ADPCM_IMA_WAV:
        avctx->frame_size = (BLKSIZE - 4 * avctx->channels) * 8 / (4 * avctx->channels) + 1; /* each 16 bits sample gives one nibble */
                                                             /* and we have 4 bytes per channel overhead */
        avctx->block_align = BLKSIZE;
        /* seems frame_size isn't taken into account... have to buffer the samples :-( */
        break;
    case CODEC_ID_ADPCM_MS:
        fprintf(stderr, "ADPCM: codec admcp_ms unsupported for encoding !\n");
        return -1;
        break;
    default:
        return -1;
        break;
    }
    return 0;
}

static int adpcm_encode_close(AVCodecContext *avctx)
{
    /* nothing to free */
    return 0;
}


static inline unsigned char adpcm_ima_compress_sample(ADPCMChannelStatus *c, short sample)
{
    int step_index;
    unsigned char nibble;
    
    int sign = 0; /* sign bit of the nibble (MSB) */
    int delta, predicted_delta;

    delta = sample - c->prev_sample;

    if (delta < 0) {
        sign = 1;
        delta = -delta;
    }

    step_index = c->step_index;

    /* nibble = 4 * delta / step_table[step_index]; */
    nibble = (delta << 2) / step_table[step_index];

    if (nibble > 7)
        nibble = 7;

    step_index += index_table[nibble];
    if (step_index < 0)
        step_index = 0;
    if (step_index > 88)
        step_index = 88;

    /* what the decoder will find */
    predicted_delta = ((step_table[step_index] * nibble) / 4) + (step_table[step_index] / 8);

    if (sign)
        c->prev_sample -= predicted_delta;
    else
        c->prev_sample += predicted_delta;

    CLAMP_TO_SHORT(c->prev_sample);


    nibble += sign << 3; /* sign * 8 */   

    /* save back */
    c->step_index = step_index;

    return nibble;
}

static int adpcm_encode_frame(AVCodecContext *avctx,
			    unsigned char *frame, int buf_size, void *data)
{
    int n;
    short *samples;
    unsigned char *dst;
    ADPCMContext *c = avctx->priv_data;

    dst = frame;
    samples = (short *)data;
/*    n = (BLKSIZE - 4 * avctx->channels) / (2 * 8 * avctx->channels); */

    switch(avctx->codec->id) {
    case CODEC_ID_ADPCM_IMA_QT: /* XXX: can't test until we get .mov writer */
        break;
    case CODEC_ID_ADPCM_IMA_WAV:
        n = avctx->frame_size / 8;
            c->status[0].prev_sample = (signed short)samples[0]; /* XXX */
/*            c->status[0].step_index = 0; *//* XXX: not sure how to init the state machine */
            *dst++ = (c->status[0].prev_sample) & 0xFF; /* little endian */
            *dst++ = (c->status[0].prev_sample >> 8) & 0xFF;
            *dst++ = (unsigned char)c->status[0].step_index;
            *dst++ = 0; /* unknown */
            samples++;
            if (avctx->channels == 2) {
                c->status[1].prev_sample = (signed short)samples[0];
/*                c->status[1].step_index = 0; */
                *dst++ = (c->status[1].prev_sample) & 0xFF;
                *dst++ = (c->status[1].prev_sample >> 8) & 0xFF;
                *dst++ = (unsigned char)c->status[1].step_index;
                *dst++ = 0;
                samples++;
            }
        
            /* stereo: 4 bytes (8 samples) for left, 4 bytes for right, 4 bytes left, ... */
            for (; n>0; n--) {
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[0]) & 0x0F;
                *dst |= (adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels]) << 4) & 0xF0;
                dst++;
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 2]) & 0x0F;
                *dst |= (adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 3]) << 4) & 0xF0;
                dst++;
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 4]) & 0x0F;
                *dst |= (adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 5]) << 4) & 0xF0;
                dst++;
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 6]) & 0x0F;
                *dst |= (adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 7]) << 4) & 0xF0;
                dst++;
                /* right channel */
                if (avctx->channels == 2) {
                    *dst = adpcm_ima_compress_sample(&c->status[1], samples[1]);
                    *dst |= adpcm_ima_compress_sample(&c->status[1], samples[3]) << 4;
                    dst++;
                    *dst = adpcm_ima_compress_sample(&c->status[1], samples[5]);
                    *dst |= adpcm_ima_compress_sample(&c->status[1], samples[7]) << 4;
                    dst++;
                    *dst = adpcm_ima_compress_sample(&c->status[1], samples[9]);
                    *dst |= adpcm_ima_compress_sample(&c->status[1], samples[11]) << 4;
                    dst++;
                    *dst = adpcm_ima_compress_sample(&c->status[1], samples[13]);
                    *dst |= adpcm_ima_compress_sample(&c->status[1], samples[15]) << 4;
                    dst++;
                }
                samples += 8 * avctx->channels;
            }
        break;
    default:
        return -1;
    }
    avctx->key_frame = 1;
    return dst - frame;
}

static int adpcm_decode_init(AVCodecContext * avctx)
{
    ADPCMContext *c = avctx->priv_data;

    c->channel = 0;
    c->status[0].predictor = c->status[1].predictor = 0;
    c->status[0].step_index = c->status[1].step_index = 0;