annotate ffmpeg/libavcodec/ra144dec.c @ 13:844d341cf643 tip

Back up before ISMIR

/*
 * Real Audio 1.0 (14.4K)
 *
 * Copyright (c) 2008 Vitor Sessak
 * Copyright (c) 2003 Nick Kurshev
 *     Based on public domain decoder at http://www.honeypot.net/audio
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg 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.
 *
 * FFmpeg 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 FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/channel_layout.h"
#include "avcodec.h"
#include "get_bits.h"
#include "internal.h"
#include "ra144.h"


static av_cold int ra144_decode_init(AVCodecContext * avctx)
{
    RA144Context *ractx = avctx->priv_data;

    ractx->avctx = avctx;

    ractx->lpc_coef[0] = ractx->lpc_tables[0];
    ractx->lpc_coef[1] = ractx->lpc_tables[1];

    avctx->channels       = 1;
    avctx->channel_layout = AV_CH_LAYOUT_MONO;
    avctx->sample_fmt     = AV_SAMPLE_FMT_S16;

    return 0;
}

static void do_output_subblock(RA144Context *ractx, const int16_t  *lpc_coefs,
                               int gval, GetBitContext *gb)
{
    int cba_idx = get_bits(gb, 7); // index of the adaptive CB, 0 if none
    int gain    = get_bits(gb, 8);
    int cb1_idx = get_bits(gb, 7);
    int cb2_idx = get_bits(gb, 7);

    ff_subblock_synthesis(ractx, lpc_coefs, cba_idx, cb1_idx, cb2_idx, gval,
                          gain);
}

/** Uncompress one block (20 bytes -> 160*2 bytes). */
static int ra144_decode_frame(AVCodecContext * avctx, void *data,
                              int *got_frame_ptr, AVPacket *avpkt)
{
    AVFrame *frame     = data;
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    static const uint8_t sizes[LPC_ORDER] = {6, 5, 5, 4, 4, 3, 3, 3, 3, 2};
    unsigned int refl_rms[NBLOCKS];           // RMS of the reflection coefficients
    int16_t block_coefs[NBLOCKS][LPC_ORDER];  // LPC coefficients of each sub-block
    unsigned int lpc_refl[LPC_ORDER];         // LPC reflection coefficients of the frame
    int i, j;
    int ret;
    int16_t *samples;
    unsigned int energy;

    RA144Context *ractx = avctx->priv_data;
    GetBitContext gb;

    if (buf_size < FRAMESIZE) {
        av_log(avctx, AV_LOG_ERROR,
               "Frame too small (%d bytes). Truncated file?\n", buf_size);
        *got_frame_ptr = 0;
        return AVERROR_INVALIDDATA;
    }

    /* get output buffer */
    frame->nb_samples = NBLOCKS * BLOCKSIZE;
    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
        return ret;
    samples = (int16_t *)frame->data[0];

    init_get_bits(&gb, buf, FRAMESIZE * 8);

    for (i = 0; i < LPC_ORDER; i++)
        lpc_refl[i] = ff_lpc_refl_cb[i][get_bits(&gb, sizes[i])];

    ff_eval_coefs(ractx->lpc_coef[0], lpc_refl);
    ractx->lpc_refl_rms[0] = ff_rms(lpc_refl);

    energy = ff_energy_tab[get_bits(&gb, 5)];

    refl_rms[0] = ff_interp(ractx, block_coefs[0], 1, 1, ractx->old_energy);
    refl_rms[1] = ff_interp(ractx, block_coefs[1], 2,
                            energy <= ractx->old_energy,
                            ff_t_sqrt(energy*ractx->old_energy) >> 12);
    refl_rms[2] = ff_interp(ractx, block_coefs[2], 3, 0, energy);
    refl_rms[3] = ff_rescale_rms(ractx->lpc_refl_rms[0], energy);

    ff_int_to_int16(block_coefs[3], ractx->lpc_coef[0]);

    for (i=0; i < NBLOCKS; i++) {
        do_output_subblock(ractx, block_coefs[i], refl_rms[i], &gb);

        for (j=0; j < BLOCKSIZE; j++)
            *samples++ = av_clip_int16(ractx->curr_sblock[j + 10] << 2);
    }

    ractx->old_energy = energy;
    ractx->lpc_refl_rms[1] = ractx->lpc_refl_rms[0];

    FFSWAP(unsigned int *, ractx->lpc_coef[0], ractx->lpc_coef[1]);

    *got_frame_ptr = 1;

    return FRAMESIZE;
}

AVCodec ff_ra_144_decoder = {
    .name           = "real_144",
    .type           = AVMEDIA_TYPE_AUDIO,
    .id             = AV_CODEC_ID_RA_144,
    .priv_data_size = sizeof(RA144Context),
    .init           = ra144_decode_init,
    .decode         = ra144_decode_frame,
    .capabilities   = CODEC_CAP_DR1,
    .long_name      = NULL_IF_CONFIG_SMALL("RealAudio 1.0 (14.4K)"),
};