You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.

142 lines
3.8KB

  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 "ac3enc.h"
  30. #define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED
  31. #include "ac3enc_opts_template.c"
  32. static AVClass ac3enc_class = { "Fixed-Point AC-3 Encoder", av_default_item_name,
  33. ac3fixed_options, LIBAVUTIL_VERSION_INT };
  34. #include "ac3enc_template.c"
  35. /**
  36. * Finalize MDCT and free allocated memory.
  37. */
  38. av_cold void AC3_NAME(mdct_end)(AC3MDCTContext *mdct)
  39. {
  40. ff_mdct_end(&mdct->fft);
  41. }
  42. /**
  43. * Initialize MDCT tables.
  44. * @param nbits log2(MDCT size)
  45. */
  46. av_cold int AC3_NAME(mdct_init)(AVCodecContext *avctx, AC3MDCTContext *mdct,
  47. int nbits)
  48. {
  49. int ret = ff_mdct_init(&mdct->fft, nbits, 0, -1.0);
  50. mdct->window = ff_ac3_window;
  51. return ret;
  52. }
  53. /**
  54. * Apply KBD window to input samples prior to MDCT.
  55. */
  56. void AC3_NAME(apply_window)(DSPContext *dsp, int16_t *output,
  57. const int16_t *input, const int16_t *window,
  58. unsigned int len)
  59. {
  60. dsp->apply_window_int16(output, input, window, len);
  61. }
  62. /**
  63. * Calculate the log2() of the maximum absolute value in an array.
  64. * @param tab input array
  65. * @param n number of values in the array
  66. * @return log2(max(abs(tab[])))
  67. */
  68. static int log2_tab(AC3EncodeContext *s, int16_t *src, int len)
  69. {
  70. int v = s->ac3dsp.ac3_max_msb_abs_int16(src, len);
  71. return av_log2(v);
  72. }
  73. /**
  74. * Normalize the input samples to use the maximum available precision.
  75. * This assumes signed 16-bit input samples.
  76. *
  77. * @return exponent shift
  78. */
  79. int AC3_NAME(normalize_samples)(AC3EncodeContext *s)
  80. {
  81. int v = 14 - log2_tab(s, s->windowed_samples, AC3_WINDOW_SIZE);
  82. if (v > 0)
  83. s->ac3dsp.ac3_lshift_int16(s->windowed_samples, AC3_WINDOW_SIZE, v);
  84. /* +6 to right-shift from 31-bit to 25-bit */
  85. return v + 6;
  86. }
  87. /**
  88. * Scale MDCT coefficients to 25-bit signed fixed-point.
  89. */
  90. void AC3_NAME(scale_coefficients)(AC3EncodeContext *s)
  91. {
  92. int blk, ch;
  93. for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
  94. AC3Block *block = &s->blocks[blk];
  95. for (ch = 1; ch <= s->channels; ch++) {
  96. s->ac3dsp.ac3_rshift_int32(block->mdct_coef[ch], AC3_MAX_COEFS,
  97. block->coeff_shift[ch]);
  98. }
  99. }
  100. }
  101. static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx)
  102. {
  103. AC3EncodeContext *s = avctx->priv_data;
  104. s->fixed_point = 1;
  105. return ff_ac3_encode_init(avctx);
  106. }
  107. AVCodec ff_ac3_fixed_encoder = {
  108. "ac3_fixed",
  109. AVMEDIA_TYPE_AUDIO,
  110. CODEC_ID_AC3,
  111. sizeof(AC3EncodeContext),
  112. ac3_fixed_encode_init,
  113. ff_ac3_encode_frame,
  114. ff_ac3_encode_close,
  115. NULL,
  116. .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE},
  117. .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
  118. .priv_class = &ac3enc_class,
  119. .channel_layouts = ff_ac3_channel_layouts,
  120. };