1/* 2 * The simplest AC-3 encoder 3 * Copyright (c) 2000 Fabrice Bellard 4 * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com> 5 * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de> 6 * 7 * This file is part of Libav. 8 * 9 * Libav is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU Lesser General Public 11 * License as published by the Free Software Foundation; either 12 * version 2.1 of the License, or (at your option) any later version. 13 * 14 * Libav is distributed in the hope that it will be useful, 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 17 * Lesser General Public License for more details. 18 * 19 * You should have received a copy of the GNU Lesser General Public 20 * License along with Libav; if not, write to the Free Software 21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 22 */ 23 24/** 25 * @file 26 * fixed-point AC-3 encoder. 27 */ 28 29#define CONFIG_FFT_FLOAT 0 30#undef CONFIG_AC3ENC_FLOAT 31#include "ac3enc.h" 32#include "eac3enc.h" 33 34#define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED 35#include "ac3enc_opts_template.c" 36static const AVClass ac3enc_class = { "Fixed-Point AC-3 Encoder", av_default_item_name, 37 ac3fixed_options, LIBAVUTIL_VERSION_INT }; 38 39#include "ac3enc_template.c" 40 41 42/** 43 * Finalize MDCT and free allocated memory. 44 * 45 * @param s AC-3 encoder private context 46 */ 47av_cold void AC3_NAME(mdct_end)(AC3EncodeContext *s) 48{ 49 ff_mdct_end(&s->mdct); 50} 51 52 53/** 54 * Initialize MDCT tables. 55 * 56 * @param s AC-3 encoder private context 57 * @return 0 on success, negative error code on failure 58 */ 59av_cold int AC3_NAME(mdct_init)(AC3EncodeContext *s) 60{ 61 int ret = ff_mdct_init(&s->mdct, 9, 0, -1.0); 62 s->mdct_window = ff_ac3_window; 63 return ret; 64} 65 66 67/* 68 * Apply KBD window to input samples prior to MDCT. 69 */ 70static void apply_window(DSPContext *dsp, int16_t *output, const int16_t *input, 71 const int16_t *window, unsigned int len) 72{ 73 dsp->apply_window_int16(output, input, window, len); 74} 75 76 77/* 78 * Normalize the input samples to use the maximum available precision. 79 * This assumes signed 16-bit input samples. 80 */ 81static int normalize_samples(AC3EncodeContext *s) 82{ 83 int v = s->ac3dsp.ac3_max_msb_abs_int16(s->windowed_samples, AC3_WINDOW_SIZE); 84 v = 14 - av_log2(v); 85 if (v > 0) 86 s->ac3dsp.ac3_lshift_int16(s->windowed_samples, AC3_WINDOW_SIZE, v); 87 /* +6 to right-shift from 31-bit to 25-bit */ 88 return v + 6; 89} 90 91 92/* 93 * Scale MDCT coefficients to 25-bit signed fixed-point. 94 */ 95static void scale_coefficients(AC3EncodeContext *s) 96{ 97 int blk, ch; 98 99 for (blk = 0; blk < s->num_blocks; blk++) { 100 AC3Block *block = &s->blocks[blk]; 101 for (ch = 1; ch <= s->channels; ch++) { 102 s->ac3dsp.ac3_rshift_int32(block->mdct_coef[ch], AC3_MAX_COEFS, 103 block->coeff_shift[ch]); 104 } 105 } 106} 107 108 109/* 110 * Clip MDCT coefficients to allowable range. 111 */ 112static void clip_coefficients(DSPContext *dsp, int32_t *coef, unsigned int len) 113{ 114 dsp->vector_clip_int32(coef, coef, COEF_MIN, COEF_MAX, len); 115} 116 117 118/* 119 * Calculate a single coupling coordinate. 120 */ 121static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl) 122{ 123 if (energy_cpl <= COEF_MAX) { 124 return 1048576; 125 } else { 126 uint64_t coord = energy_ch / (energy_cpl >> 24); 127 uint32_t coord32 = FFMIN(coord, 1073741824); 128 coord32 = ff_sqrt(coord32) << 9; 129 return FFMIN(coord32, COEF_MAX); 130 } 131} 132 133 134static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx) 135{ 136 AC3EncodeContext *s = avctx->priv_data; 137 s->fixed_point = 1; 138 return ff_ac3_encode_init(avctx); 139} 140 141 142AVCodec ff_ac3_fixed_encoder = { 143 .name = "ac3_fixed", 144 .type = AVMEDIA_TYPE_AUDIO, 145 .id = CODEC_ID_AC3, 146 .priv_data_size = sizeof(AC3EncodeContext), 147 .init = ac3_fixed_encode_init, 148 .encode = ff_ac3_fixed_encode_frame, 149 .close = ff_ac3_encode_close, 150 .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE}, 151 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"), 152 .priv_class = &ac3enc_class, 153 .channel_layouts = ff_ac3_channel_layouts, 154}; 155