libavcodec/ac3enc_fixed.c
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00001 /*
00002  * The simplest AC-3 encoder
00003  * Copyright (c) 2000 Fabrice Bellard
00004  * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
00005  * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
00006  *
00007  * This file is part of FFmpeg.
00008  *
00009  * FFmpeg is free software; you can redistribute it and/or
00010  * modify it under the terms of the GNU Lesser General Public
00011  * License as published by the Free Software Foundation; either
00012  * version 2.1 of the License, or (at your option) any later version.
00013  *
00014  * FFmpeg is distributed in the hope that it will be useful,
00015  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00016  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00017  * Lesser General Public License for more details.
00018  *
00019  * You should have received a copy of the GNU Lesser General Public
00020  * License along with FFmpeg; if not, write to the Free Software
00021  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00022  */
00023 
00029 #define CONFIG_FFT_FLOAT 0
00030 #undef CONFIG_AC3ENC_FLOAT
00031 #include "ac3enc.h"
00032 #include "eac3enc.h"
00033 
00034 #define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED
00035 #include "ac3enc_opts_template.c"
00036 static const AVClass ac3enc_class = { "Fixed-Point AC-3 Encoder", av_default_item_name,
00037                                       ac3fixed_options, LIBAVUTIL_VERSION_INT };
00038 
00039 #include "ac3enc_template.c"
00040 
00041 
00047 av_cold void AC3_NAME(mdct_end)(AC3EncodeContext *s)
00048 {
00049     ff_mdct_end(&s->mdct);
00050 }
00051 
00052 
00059 av_cold int AC3_NAME(mdct_init)(AC3EncodeContext *s)
00060 {
00061     int ret = ff_mdct_init(&s->mdct, 9, 0, -1.0);
00062     s->mdct_window = ff_ac3_window;
00063     return ret;
00064 }
00065 
00066 
00067 /*
00068  * Apply KBD window to input samples prior to MDCT.
00069  */
00070 static void apply_window(DSPContext *dsp, int16_t *output, const int16_t *input,
00071                          const int16_t *window, unsigned int len)
00072 {
00073     dsp->apply_window_int16(output, input, window, len);
00074 }
00075 
00076 
00077 /*
00078  * Normalize the input samples to use the maximum available precision.
00079  * This assumes signed 16-bit input samples.
00080  */
00081 static int normalize_samples(AC3EncodeContext *s)
00082 {
00083     int v = s->ac3dsp.ac3_max_msb_abs_int16(s->windowed_samples, AC3_WINDOW_SIZE);
00084     v = 14 - av_log2(v);
00085     if (v > 0)
00086         s->ac3dsp.ac3_lshift_int16(s->windowed_samples, AC3_WINDOW_SIZE, v);
00087     /* +6 to right-shift from 31-bit to 25-bit */
00088     return v + 6;
00089 }
00090 
00091 
00092 /*
00093  * Scale MDCT coefficients to 25-bit signed fixed-point.
00094  */
00095 static void scale_coefficients(AC3EncodeContext *s)
00096 {
00097     int blk, ch;
00098 
00099     for (blk = 0; blk < s->num_blocks; blk++) {
00100         AC3Block *block = &s->blocks[blk];
00101         for (ch = 1; ch <= s->channels; ch++) {
00102             s->ac3dsp.ac3_rshift_int32(block->mdct_coef[ch], AC3_MAX_COEFS,
00103                                        block->coeff_shift[ch]);
00104         }
00105     }
00106 }
00107 
00108 static void sum_square_butterfly(AC3EncodeContext *s, int64_t sum[4],
00109                                  const int32_t *coef0, const int32_t *coef1,
00110                                  int len)
00111 {
00112     s->ac3dsp.sum_square_butterfly_int32(sum, coef0, coef1, len);
00113 }
00114 
00115 /*
00116  * Clip MDCT coefficients to allowable range.
00117  */
00118 static void clip_coefficients(DSPContext *dsp, int32_t *coef, unsigned int len)
00119 {
00120     dsp->vector_clip_int32(coef, coef, COEF_MIN, COEF_MAX, len);
00121 }
00122 
00123 
00124 /*
00125  * Calculate a single coupling coordinate.
00126  */
00127 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
00128 {
00129     if (energy_cpl <= COEF_MAX) {
00130         return 1048576;
00131     } else {
00132         uint64_t coord   = energy_ch / (energy_cpl >> 24);
00133         uint32_t coord32 = FFMIN(coord, 1073741824);
00134         coord32          = ff_sqrt(coord32) << 9;
00135         return FFMIN(coord32, COEF_MAX);
00136     }
00137 }
00138 
00139 
00140 static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx)
00141 {
00142     AC3EncodeContext *s = avctx->priv_data;
00143     s->fixed_point = 1;
00144     return ff_ac3_encode_init(avctx);
00145 }
00146 
00147 
00148 AVCodec ff_ac3_fixed_encoder = {
00149     .name           = "ac3_fixed",
00150     .type           = AVMEDIA_TYPE_AUDIO,
00151     .id             = CODEC_ID_AC3,
00152     .priv_data_size = sizeof(AC3EncodeContext),
00153     .init           = ac3_fixed_encode_init,
00154     .encode         = ff_ac3_fixed_encode_frame,
00155     .close          = ff_ac3_encode_close,
00156     .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE},
00157     .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
00158     .priv_class = &ac3enc_class,
00159     .channel_layouts = ff_ac3_channel_layouts,
00160 };