libavcodec/ac3enc_fixed.c

   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 FFT_FLOAT 0
  30 #undef CONFIG_AC3ENC_FLOAT
  31 #include "internal.h"
  32 #include "audiodsp.h"
  33 #include "ac3enc.h"
  34 #include "eac3enc.h"
  35
  36 #define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED
  37 #include "ac3enc_opts_template.c"
  38
  39 static const AVClass ac3enc_class = {
  40     .class_name = "Fixed-Point AC-3 Encoder",
  41     .item_name  = av_default_item_name,
  42     .option     = ac3_options,
  43     .version    = LIBAVUTIL_VERSION_INT,
  44 };
  45
  46 /*
  47  * Normalize the input samples to use the maximum available precision.
  48  * This assumes signed 16-bit input samples.
  49  */
  50 static int normalize_samples(AC3EncodeContext *s)
  51 {
  52     int v = s->ac3dsp.ac3_max_msb_abs_int16(s->windowed_samples, AC3_WINDOW_SIZE);
  53     v = 14 - av_log2(v);
  54     if (v > 0)
  55         s->ac3dsp.ac3_lshift_int16(s->windowed_samples, AC3_WINDOW_SIZE, v);
  56     /* +6 to right-shift from 31-bit to 25-bit */
  57     return v + 6;
  58 }
  59
  60
  61 /*
  62  * Scale MDCT coefficients to 25-bit signed fixed-point.
  63  */
  64 static void scale_coefficients(AC3EncodeContext *s)
  65 {
  66     int blk, ch;
  67
  68     for (blk = 0; blk < s->num_blocks; blk++) {
  69         AC3Block *block = &s->blocks[blk];
  70         for (ch = 1; ch <= s->channels; ch++) {
  71             s->ac3dsp.ac3_rshift_int32(block->mdct_coef[ch], AC3_MAX_COEFS,
  72                                        block->coeff_shift[ch]);
  73         }
  74     }
  75 }
  76
  77
  78 /*
  79  * Clip MDCT coefficients to allowable range.
  80  */
  81 static void clip_coefficients(AudioDSPContext *adsp, int32_t *coef,
  82                               unsigned int len)
  83 {
  84     adsp->vector_clip_int32(coef, coef, COEF_MIN, COEF_MAX, len);
  85 }
  86
  87
  88 /*
  89  * Calculate a single coupling coordinate.
  90  */
  91 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
  92 {
  93     if (energy_cpl <= COEF_MAX) {
  94         return 1048576;
  95     } else {
  96         uint64_t coord   = energy_ch / (energy_cpl >> 24);
  97         uint32_t coord32 = FFMIN(coord, 1073741824);
  98         coord32          = ff_sqrt(coord32) << 9;
  99         return FFMIN(coord32, COEF_MAX);
 100     }
 101 }
 102
 103
 104 #include "ac3enc_template.c"
 105
 106
 107 /**
 108  * Finalize MDCT and free allocated memory.
 109  *
 110  * @param s  AC-3 encoder private context
 111  */
 112 av_cold void ff_ac3_fixed_mdct_end(AC3EncodeContext *s)
 113 {
 114     ff_mdct_end(&s->mdct);
 115 }
 116
 117
 118 /**
 119  * Initialize MDCT tables.
 120  *
 121  * @param s  AC-3 encoder private context
 122  * @return   0 on success, negative error code on failure
 123  */
 124 av_cold int ff_ac3_fixed_mdct_init(AC3EncodeContext *s)
 125 {
 126     int ret = ff_mdct_init(&s->mdct, 9, 0, -1.0);
 127     s->mdct_window = ff_ac3_window;
 128     return ret;
 129 }
 130
 131
 132 static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx)
 133 {
 134     AC3EncodeContext *s = avctx->priv_data;
 135     s->fixed_point = 1;
 136     return ff_ac3_encode_init(avctx);
 137 }
 138
 139
 140 AVCodec ff_ac3_fixed_encoder = {
 141     .name            = "ac3_fixed",
 142     .long_name       = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
 143     .type            = AVMEDIA_TYPE_AUDIO,
 144     .id              = AV_CODEC_ID_AC3,
 145     .priv_data_size  = sizeof(AC3EncodeContext),
 146     .init            = ac3_fixed_encode_init,
 147     .encode2         = ff_ac3_fixed_encode_frame,
 148     .close           = ff_ac3_encode_close,
 149     .sample_fmts     = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16P,
 150                                                       AV_SAMPLE_FMT_NONE },
 151     .priv_class      = &ac3enc_class,
 152     .channel_layouts = ff_ac3_channel_layouts,
 153     .defaults        = ac3_defaults,
 154 };