ac3enc_float.c 4.12 KB
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/*
 * The simplest AC-3 encoder
 * Copyright (c) 2000 Fabrice Bellard
 * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
 * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * 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.
 *
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 * Libav is distributed in the hope that it will be useful,
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 * 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
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * floating-point AC-3 encoder.
 */

#define CONFIG_AC3ENC_FLOAT 1
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#include "internal.h"
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#include "audiodsp.h"
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#include "ac3enc.h"
#include "eac3enc.h"
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#include "kbdwin.h"
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#define AC3ENC_TYPE AC3ENC_TYPE_AC3
#include "ac3enc_opts_template.c"
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static const AVClass ac3enc_class = { "AC-3 Encoder", av_default_item_name,
                                      ac3_options, LIBAVUTIL_VERSION_INT };
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#include "ac3enc_template.c"


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/**
 * Finalize MDCT and free allocated memory.
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 *
 * @param s  AC-3 encoder private context
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 */
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av_cold void ff_ac3_float_mdct_end(AC3EncodeContext *s)
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{
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    ff_mdct_end(&s->mdct);
    av_freep(&s->mdct_window);
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}


/**
 * Initialize MDCT tables.
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 *
 * @param s  AC-3 encoder private context
 * @return   0 on success, negative error code on failure
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 */
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av_cold int ff_ac3_float_mdct_init(AC3EncodeContext *s)
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{
    float *window;
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    int i, n, n2;
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    n  = 1 << 9;
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    n2 = n >> 1;

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    window = av_malloc(n * sizeof(*window));
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    if (!window) {
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        av_log(s->avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
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        return AVERROR(ENOMEM);
    }
    ff_kbd_window_init(window, 5.0, n2);
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    for (i = 0; i < n2; i++)
        window[n-1-i] = window[i];
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    s->mdct_window = window;
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    return ff_mdct_init(&s->mdct, 9, 0, -2.0 / n);
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}


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/*
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 * Normalize the input samples.
 * Not needed for the floating-point encoder.
 */
static int normalize_samples(AC3EncodeContext *s)
{
    return 0;
}


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/*
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 * Scale MDCT coefficients from float to 24-bit fixed-point.
 */
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static void scale_coefficients(AC3EncodeContext *s)
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{
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    int chan_size = AC3_MAX_COEFS * s->num_blocks;
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    int cpl       = s->cpl_on;
    s->ac3dsp.float_to_fixed24(s->fixed_coef_buffer + (chan_size * !cpl),
                               s->mdct_coef_buffer  + (chan_size * !cpl),
                               chan_size * (s->channels + cpl));
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}


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/*
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 * Clip MDCT coefficients to allowable range.
 */
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static void clip_coefficients(AudioDSPContext *adsp, float *coef,
                              unsigned int len)
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{
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    adsp->vector_clipf(coef, coef, COEF_MIN, COEF_MAX, len);
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}


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/*
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 * Calculate a single coupling coordinate.
 */
static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
{
    float coord = 0.125;
    if (energy_cpl > 0)
        coord *= sqrtf(energy_ch / energy_cpl);
    return FFMIN(coord, COEF_MAX);
}

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av_cold int ff_ac3_float_encode_init(AVCodecContext *avctx)
{
    AC3EncodeContext *s = avctx->priv_data;
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    avpriv_float_dsp_init(&s->fdsp, avctx->flags & AV_CODEC_FLAG_BITEXACT);
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    return ff_ac3_encode_init(avctx);
}
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AVCodec ff_ac3_encoder = {
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    .name            = "ac3",
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    .long_name       = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
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    .type            = AVMEDIA_TYPE_AUDIO,
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    .id              = AV_CODEC_ID_AC3,
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    .priv_data_size  = sizeof(AC3EncodeContext),
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    .init            = ff_ac3_float_encode_init,
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    .encode2         = ff_ac3_float_encode_frame,
    .close           = ff_ac3_encode_close,
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    .sample_fmts     = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_FLTP,
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                                                      AV_SAMPLE_FMT_NONE },
    .priv_class      = &ac3enc_class,
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    .channel_layouts = ff_ac3_channel_layouts,
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    .defaults        = ac3_defaults,
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};