FFmpeg/libavcodec/adxdec.c

/*
 * ADX ADPCM codecs
 * Copyright (c) 2001,2003 BERO
 *
 * This file is part of Libav.
 *
 * Libav 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 2.1 of the License, or (at your option) any later version.
 *
 * Libav 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 Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/intreadwrite.h"
#include "avcodec.h"
#include "adx.h"

/**
 * @file
 * SEGA CRI adx codecs.
 *
 * Reference documents:
 * http://ku-www.ss.titech.ac.jp/~yatsushi/adx.html
 * adx2wav & wav2adx http://www.geocities.co.jp/Playtown/2004/
 */

static av_cold int adx_decode_init(AVCodecContext *avctx)
{
    avctx->sample_fmt = AV_SAMPLE_FMT_S16;
    return 0;
}

/**
 * Decode 32 samples from 18 bytes.
 *
 * A 16-bit scalar value is applied to 32 residuals, which then have a
 * 2nd-order LPC filter applied to it to form the output signal for a single
 * channel.
 */
static void adx_decode(int16_t *out, const uint8_t *in, ADXChannelState *prev)
{
    int scale = AV_RB16(in);
    int i;
    int s0, s1, s2, d;

    in += 2;
    s1 = prev->s1;
    s2 = prev->s2;
    for (i = 0; i < 16; i++) {
        d  = in[i];
        d  = (signed char)d >> 4;
        s0 = (BASEVOL * d * scale + SCALE1 * s1 - SCALE2 * s2) >> 14;
        s2 = s1;
        s1 = av_clip_int16(s0);
        *out++ = s1;

        d  = in[i];
        d  = (signed char)(d << 4) >> 4;
        s0 = (BASEVOL * d * scale + SCALE1 * s1 - SCALE2 * s2) >> 14;
        s2 = s1;
        s1 = av_clip_int16(s0);
        *out++ = s1;
    }
    prev->s1 = s1;
    prev->s2 = s2;
}

static void adx_decode_stereo(int16_t *out,const uint8_t *in,
                              ADXChannelState *prev)
{
    short tmp[32*2];
    int i;

    adx_decode(tmp,    in,    prev);
    adx_decode(tmp+32, in+18, prev+1);
    for (i = 0; i < 32; i++) {
        out[i*2  ] = tmp[i   ];
        out[i*2+1] = tmp[i+32];
    }
}

/**
 * Decode stream header.
 *
 * @param avctx   codec context
 * @param buf     packet data
 * @param bufsize packet size
 * @return data offset or 0 if header is invalid
 */
static int adx_decode_header(AVCodecContext *avctx, const uint8_t *buf,
                             int bufsize)
{
    int offset;

    if (buf[0] != 0x80)
        return 0;
    offset = (AV_RB32(buf) ^ 0x80000000) + 4;
    if (bufsize < offset || memcmp(buf + offset - 6, "(c)CRI", 6))
        return 0;

    avctx->channels    = buf[7];
    avctx->sample_rate = AV_RB32(buf + 8);
    avctx->bit_rate    = avctx->sample_rate * avctx->channels * 18 * 8 / 32;

    return offset;
}

static int adx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
                            AVPacket *avpkt)
{
    const uint8_t *buf0 = avpkt->data;
    int buf_size        = avpkt->size;
    ADXContext *c       = avctx->priv_data;
    int16_t *samples    = data;
    const uint8_t *buf  = buf0;
    int rest            = buf_size;

    if (!c->header_parsed) {
        int hdrsize = adx_decode_header(avctx, buf, rest);
        if (!hdrsize)
            return -1;
        c->header_parsed = 1;
        buf  += hdrsize;
        rest -= hdrsize;
    }

    /* 18 bytes of data are expanded into 32*2 bytes of audio,
       so guard against buffer overflows */
    if (rest / 18 > *data_size / 64)
        rest = (*data_size / 64) * 18;

    if (c->in_temp) {
        int copysize = 18 * avctx->channels - c->in_temp;
        memcpy(c->dec_temp + c->in_temp, buf, copysize);
        rest -= copysize;
        buf  += copysize;
        if (avctx->channels == 1) {
            adx_decode(samples, c->dec_temp, c->prev);
            samples += 32;
        } else {
            adx_decode_stereo(samples, c->dec_temp, c->prev);
            samples += 32*2;
        }
    }

    if (avctx->channels == 1) {
        while (rest >= 18) {
            adx_decode(samples, buf, c->prev);
            rest    -= 18;
            buf     += 18;
            samples += 32;
        }
    } else {
        while (rest >= 18 * 2) {
            adx_decode_stereo(samples, buf, c->prev);
            rest    -= 18 * 2;
            buf     += 18 * 2;
            samples += 32 * 2;
        }
    }

    c->in_temp = rest;
    if (rest) {
        memcpy(c->dec_temp, buf, rest);
        buf += rest;
    }
    *data_size = (uint8_t*)samples - (uint8_t*)data;
    return buf - buf0;
}

AVCodec ff_adpcm_adx_decoder = {
    .name           = "adpcm_adx",
    .type           = AVMEDIA_TYPE_AUDIO,
    .id             = CODEC_ID_ADPCM_ADX,
    .priv_data_size = sizeof(ADXContext),
    .init           = adx_decode_init,
    .decode         = adx_decode_frame,
    .long_name      = NULL_IF_CONFIG_SMALL("SEGA CRI ADX ADPCM"),
};