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 CONFIG_FFT_FLOAT 0
  30 #undef CONFIG_AC3ENC_FLOAT
  31 #include "internal.h"
  32 #include "ac3enc.h"
  33 #include "eac3enc.h"
  34
  35 #define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED
  36 #include "ac3enc_opts_template.c"
  37 static const AVClass ac3enc_class = { "Fixed-Point AC-3 Encoder", av_default_item_name,
  38                                       ac3_options, LIBAVUTIL_VERSION_INT };
  39
  40 #include "ac3enc_template.c"
  41
  42
  43 /**
  44  * Finalize MDCT and free allocated memory.
  45  *
  46  * @param s  AC-3 encoder private context
  47  */
  48 av_cold void AC3_NAME(mdct_end)(AC3EncodeContext *s)
  49 {
  50     ff_mdct_end(&s->mdct);
  51 }
  52
  53
  54 /**
  55  * Initialize MDCT tables.
  56  *
  57  * @param s  AC-3 encoder private context
  58  * @return   0 on success, negative error code on failure
  59  */
  60 av_cold int AC3_NAME(mdct_init)(AC3EncodeContext *s)
  61 {
  62     int ret = ff_mdct_init(&s->mdct, 9, 0, -1.0);
  63     s->mdct_window = ff_ac3_window;
  64     return ret;
  65 }
  66
  67
  68 /*
  69  * Apply KBD window to input samples prior to MDCT.
  70  */
  71 static void apply_window(void *dsp, int16_t *output, const int16_t *input,
  72                          const int16_t *window, unsigned int len)
  73 {
  74     DSPContext *dsp0 = dsp;
  75     dsp0->apply_window_int16(output, input, window, len);
  76 }
  77
  78
  79 /*
  80  * Normalize the input samples to use the maximum available precision.
  81  * This assumes signed 16-bit input samples.
  82  */
  83 static int normalize_samples(AC3EncodeContext *s)
  84 {
  85     int v = s->ac3dsp.ac3_max_msb_abs_int16(s->windowed_samples, AC3_WINDOW_SIZE);
  86     v = 14 - av_log2(v);
  87     if (v > 0)
  88         s->ac3dsp.ac3_lshift_int16(s->windowed_samples, AC3_WINDOW_SIZE, v);
  89     /* +6 to right-shift from 31-bit to 25-bit */
  90     return v + 6;
  91 }
  92
  93
  94 /*
  95  * Scale MDCT coefficients to 25-bit signed fixed-point.
  96  */
  97 static void scale_coefficients(AC3EncodeContext *s)
  98 {
  99     int blk, ch;
 100
 101     for (blk = 0; blk < s->num_blocks; blk++) {
 102         AC3Block *block = &s->blocks[blk];
 103         for (ch = 1; ch <= s->channels; ch++) {
 104             s->ac3dsp.ac3_rshift_int32(block->mdct_coef[ch], AC3_MAX_COEFS,
 105                                        block->coeff_shift[ch]);
 106         }
 107     }
 108 }
 109
 110
 111 /*
 112  * Clip MDCT coefficients to allowable range.
 113  */
 114 static void clip_coefficients(DSPContext *dsp, int32_t *coef, unsigned int len)
 115 {
 116     dsp->vector_clip_int32(coef, coef, COEF_MIN, COEF_MAX, len);
 117 }
 118
 119
 120 /*
 121  * Calculate a single coupling coordinate.
 122  */
 123 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
 124 {
 125     if (energy_cpl <= COEF_MAX) {
 126         return 1048576;
 127     } else {
 128         uint64_t coord   = energy_ch / (energy_cpl >> 24);
 129         uint32_t coord32 = FFMIN(coord, 1073741824);
 130         coord32          = ff_sqrt(coord32) << 9;
 131         return FFMIN(coord32, COEF_MAX);
 132     }
 133 }
 134
 135
 136 static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx)
 137 {
 138     AC3EncodeContext *s = avctx->priv_data;
 139     s->fixed_point = 1;
 140     return ff_ac3_encode_init(avctx);
 141 }
 142
 143
 144 AVCodec ff_ac3_fixed_encoder = {
 145     .name            = "ac3_fixed",
 146     .type            = AVMEDIA_TYPE_AUDIO,
 147     .id              = AV_CODEC_ID_AC3,
 148     .priv_data_size  = sizeof(AC3EncodeContext),
 149     .init            = ac3_fixed_encode_init,
 150     .encode2         = ff_ac3_fixed_encode_frame,
 151     .close           = ff_ac3_encode_close,
 152     .sample_fmts     = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16P,
 153                                                       AV_SAMPLE_FMT_NONE },
 154     .long_name       = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
 155     .priv_class      = &ac3enc_class,
 156     .channel_layouts = ff_ac3_channel_layouts,
 157     .defaults        = ac3_defaults,
 158 };