/*
  * The simplest AC-3 encoder
  * Copyright (c) 2000 Fabrice Bellard
  * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
  * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**
  * @file
  * fixed-point AC-3 encoder.
  */
 

 #define CONFIG_FFT_FLOAT 0

 #undef CONFIG_AC3ENC_FLOAT

 #include "ac3enc.h"
 
 #define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED
 #include "ac3enc_opts_template.c"
 static AVClass ac3enc_class = { "Fixed-Point AC-3 Encoder", av_default_item_name,
                                 ac3fixed_options, LIBAVUTIL_VERSION_INT };
 
 #include "ac3enc_template.c"

 
 
 /**
  * Finalize MDCT and free allocated memory.
  */

 av_cold void AC3_NAME(mdct_end)(AC3MDCTContext *mdct)

 {

     ff_mdct_end(&mdct->fft);

 }
 
 
 /**
  * Initialize MDCT tables.
  * @param nbits log2(MDCT size)
  */

 av_cold int AC3_NAME(mdct_init)(AVCodecContext *avctx, AC3MDCTContext *mdct,
                                 int nbits)

 {

     int ret = ff_mdct_init(&mdct->fft, nbits, 0, -1.0);

     mdct->window = ff_ac3_window;

     return ret;

 }
 
 
 /**
  * Apply KBD window to input samples prior to MDCT.
  */

 void AC3_NAME(apply_window)(DSPContext *dsp, int16_t *output,
                             const int16_t *input, const int16_t *window,
                             unsigned int len)

 {

     dsp->apply_window_int16(output, input, window, len);

 }
 
 
 /**
  * Calculate the log2() of the maximum absolute value in an array.
  * @param tab input array
  * @param n   number of values in the array
  * @return    log2(max(abs(tab[])))
  */

 static int log2_tab(AC3EncodeContext *s, int16_t *src, int len)

 {

     int v = s->ac3dsp.ac3_max_msb_abs_int16(src, len);

     return av_log2(v);
 }
 
 
 /**
  * Normalize the input samples to use the maximum available precision.

  * This assumes signed 16-bit input samples.

  *
  * @return exponent shift
  */

 int AC3_NAME(normalize_samples)(AC3EncodeContext *s)

 {

     int v = 14 - log2_tab(s, s->windowed_samples, AC3_WINDOW_SIZE);

     if (v > 0)
         s->ac3dsp.ac3_lshift_int16(s->windowed_samples, AC3_WINDOW_SIZE, v);

     /* +6 to right-shift from 31-bit to 25-bit */
     return v + 6;

 }
 
 

 /**

  * Scale MDCT coefficients to 25-bit signed fixed-point.

  */

 void AC3_NAME(scale_coefficients)(AC3EncodeContext *s)

 {

     int blk, ch;
 
     for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
         AC3Block *block = &s->blocks[blk];

         for (ch = 1; ch <= s->channels; ch++) {

             s->ac3dsp.ac3_rshift_int32(block->mdct_coef[ch], AC3_MAX_COEFS,
                                        block->coeff_shift[ch]);

         }
     }

 }
 
 

 static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx)
 {
     AC3EncodeContext *s = avctx->priv_data;
     s->fixed_point = 1;
     return ff_ac3_encode_init(avctx);
 }
 
 

 AVCodec ff_ac3_fixed_encoder = {

     "ac3_fixed",

     AVMEDIA_TYPE_AUDIO,
     CODEC_ID_AC3,
     sizeof(AC3EncodeContext),

     ac3_fixed_encode_init,
     ff_ac3_encode_frame,
     ff_ac3_encode_close,

     NULL,
     .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE},
     .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),

     .priv_class = &ac3enc_class,

     .channel_layouts = ff_ac3_channel_layouts,

 };