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https://github.com/FFmpeg/FFmpeg.git
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137 lines
4.1 KiB
C
137 lines
4.1 KiB
C
/*
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* The simplest AC-3 encoder
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* Copyright (c) 2000 Fabrice Bellard
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* Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
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* Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* floating-point AC-3 encoder.
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*/
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#define AC3ENC_FLOAT 1
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#include "libavutil/mem.h"
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#include "audiodsp.h"
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#include "ac3enc.h"
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#include "codec_internal.h"
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#include "eac3enc.h"
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#include "kbdwin.h"
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/*
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* Scale MDCT coefficients from float to 24-bit fixed-point.
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*/
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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;
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s->ac3dsp.float_to_fixed24(s->fixed_coef_buffer + (chan_size * !cpl),
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s->mdct_coef_buffer + (chan_size * !cpl),
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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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*/
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static void clip_coefficients(AudioDSPContext *adsp, float *coef,
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unsigned int len)
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{
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adsp->vector_clipf(coef, coef, len, COEF_MIN, COEF_MAX);
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}
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/*
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* Calculate a single coupling coordinate.
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*/
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static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
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{
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float coord = 0.125;
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if (energy_cpl > 0)
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coord *= sqrtf(energy_ch / energy_cpl);
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return FFMIN(coord, COEF_MAX);
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}
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static void sum_square_butterfly(AC3EncodeContext *s, float sum[4],
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const float *coef0, const float *coef1,
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int len)
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{
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s->ac3dsp.sum_square_butterfly_float(sum, coef0, coef1, len);
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}
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#include "ac3enc_template.c"
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/**
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* Initialize MDCT tables.
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*
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* @param s AC-3 encoder private context
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* @return 0 on success, negative error code on failure
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*/
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static av_cold int ac3_float_mdct_init(AC3EncodeContext *s)
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{
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const float scale = -2.0 / AC3_WINDOW_SIZE;
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float *window = av_malloc_array(AC3_BLOCK_SIZE, sizeof(*window));
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if (!window)
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return AVERROR(ENOMEM);
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ff_kbd_window_init(window, 5.0, AC3_BLOCK_SIZE);
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s->mdct_window = window;
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return av_tx_init(&s->tx, &s->tx_fn, AV_TX_FLOAT_MDCT, 0,
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AC3_BLOCK_SIZE, &scale, 0);
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}
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av_cold int ff_ac3_float_encode_init(AVCodecContext *avctx)
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{
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AC3EncodeContext *s = avctx->priv_data;
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int ret;
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s->encode_frame = encode_frame;
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s->fdsp = avpriv_float_dsp_alloc(avctx->flags & AV_CODEC_FLAG_BITEXACT);
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if (!s->fdsp)
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return AVERROR(ENOMEM);
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ret = ac3_float_mdct_init(s);
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if (ret < 0)
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return ret;
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return ff_ac3_encode_init(avctx);
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}
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const FFCodec ff_ac3_encoder = {
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.p.name = "ac3",
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CODEC_LONG_NAME("ATSC A/52A (AC-3)"),
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.p.type = AVMEDIA_TYPE_AUDIO,
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.p.id = AV_CODEC_ID_AC3,
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.p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE,
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.priv_data_size = sizeof(AC3EncodeContext),
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.init = ff_ac3_float_encode_init,
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FF_CODEC_ENCODE_CB(ff_ac3_encode_frame),
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.close = ff_ac3_encode_close,
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.p.sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_FLTP,
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AV_SAMPLE_FMT_NONE },
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.p.priv_class = &ff_ac3enc_class,
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.p.supported_samplerates = ff_ac3_sample_rate_tab,
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.p.ch_layouts = ff_ac3_ch_layouts,
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.defaults = ff_ac3_enc_defaults,
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.caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
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};
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