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  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. * @file
  25. * fixed-point AC-3 encoder.
  26. */
  27. #define CONFIG_FFT_FLOAT 0
  28. #undef CONFIG_AC3ENC_FLOAT
  29. #include "internal.h"
  30. #include "ac3enc.h"
  31. #include "eac3enc.h"
  32. #define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED
  33. #include "ac3enc_opts_template.c"
  34. static const AVClass ac3enc_class = { "Fixed-Point AC-3 Encoder", av_default_item_name,
  35. ac3fixed_options, LIBAVUTIL_VERSION_INT };
  36. #include "ac3enc_template.c"
  37. /**
  38. * Finalize MDCT and free allocated memory.
  39. *
  40. * @param s AC-3 encoder private context
  41. */
  42. av_cold void AC3_NAME(mdct_end)(AC3EncodeContext *s)
  43. {
  44. ff_mdct_end(&s->mdct);
  45. }
  46. /**
  47. * Initialize MDCT tables.
  48. *
  49. * @param s AC-3 encoder private context
  50. * @return 0 on success, negative error code on failure
  51. */
  52. av_cold int AC3_NAME(mdct_init)(AC3EncodeContext *s)
  53. {
  54. int ret = ff_mdct_init(&s->mdct, 9, 0, -1.0);
  55. s->mdct_window = ff_ac3_window;
  56. return ret;
  57. }
  58. /*
  59. * Apply KBD window to input samples prior to MDCT.
  60. */
  61. static void apply_window(void *dsp, int16_t *output, const int16_t *input,
  62. const int16_t *window, unsigned int len)
  63. {
  64. DSPContext *dsp0 = dsp;
  65. dsp0->apply_window_int16(output, input, window, len);
  66. }
  67. /*
  68. * Normalize the input samples to use the maximum available precision.
  69. * This assumes signed 16-bit input samples.
  70. */
  71. static int normalize_samples(AC3EncodeContext *s)
  72. {
  73. int v = s->ac3dsp.ac3_max_msb_abs_int16(s->windowed_samples, AC3_WINDOW_SIZE);
  74. v = 14 - av_log2(v);
  75. if (v > 0)
  76. s->ac3dsp.ac3_lshift_int16(s->windowed_samples, AC3_WINDOW_SIZE, v);
  77. /* +6 to right-shift from 31-bit to 25-bit */
  78. return v + 6;
  79. }
  80. /*
  81. * Scale MDCT coefficients to 25-bit signed fixed-point.
  82. */
  83. static void scale_coefficients(AC3EncodeContext *s)
  84. {
  85. int blk, ch;
  86. for (blk = 0; blk < s->num_blocks; blk++) {
  87. AC3Block *block = &s->blocks[blk];
  88. for (ch = 1; ch <= s->channels; ch++) {
  89. s->ac3dsp.ac3_rshift_int32(block->mdct_coef[ch], AC3_MAX_COEFS,
  90. block->coeff_shift[ch]);
  91. }
  92. }
  93. }
  94. /*
  95. * Clip MDCT coefficients to allowable range.
  96. */
  97. static void clip_coefficients(DSPContext *dsp, int32_t *coef, unsigned int len)
  98. {
  99. dsp->vector_clip_int32(coef, coef, COEF_MIN, COEF_MAX, len);
  100. }
  101. /*
  102. * Calculate a single coupling coordinate.
  103. */
  104. static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
  105. {
  106. if (energy_cpl <= COEF_MAX) {
  107. return 1048576;
  108. } else {
  109. uint64_t coord = energy_ch / (energy_cpl >> 24);
  110. uint32_t coord32 = FFMIN(coord, 1073741824);
  111. coord32 = ff_sqrt(coord32) << 9;
  112. return FFMIN(coord32, COEF_MAX);
  113. }
  114. }
  115. static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx)
  116. {
  117. AC3EncodeContext *s = avctx->priv_data;
  118. s->fixed_point = 1;
  119. return ff_ac3_encode_init(avctx);
  120. }
  121. AVCodec ff_ac3_fixed_encoder = {
  122. .name = "ac3_fixed",
  123. .type = AVMEDIA_TYPE_AUDIO,
  124. .id = CODEC_ID_AC3,
  125. .priv_data_size = sizeof(AC3EncodeContext),
  126. .init = ac3_fixed_encode_init,
  127. .encode2 = ff_ac3_fixed_encode_frame,
  128. .close = ff_ac3_encode_close,
  129. .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
  130. AV_SAMPLE_FMT_NONE },
  131. .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
  132. .priv_class = &ac3enc_class,
  133. .channel_layouts = ff_ac3_channel_layouts,
  134. .defaults = ac3_defaults,
  135. };