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  1. /*
  2.  * Enhanced Variable Rate Codec, Service Option 3 decoder
  3.  * Copyright (c) 2013 Paul B Mahol
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU Lesser General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2.1 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15.  * Lesser General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU Lesser General Public
  18.  * License along with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. /**
  23.  * @file
  24.  * Enhanced Variable Rate Codec, Service Option 3 decoder
  25.  * @author Paul B Mahol
  26.  */
  27.  
  28. #include "libavutil/mathematics.h"
  29. #include "libavutil/opt.h"
  30. #include "avcodec.h"
  31. #include "internal.h"
  32. #include "get_bits.h"
  33. #include "evrcdata.h"
  34. #include "acelp_vectors.h"
  35. #include "lsp.h"
  36.  
  37. #define MIN_LSP_SEP (0.05 / (2.0 * M_PI))
  38. #define MIN_DELAY      20
  39. #define MAX_DELAY     120
  40. #define NB_SUBFRAMES    3
  41. #define SUBFRAME_SIZE  54
  42. #define FILTER_ORDER   10
  43. #define ACB_SIZE      128
  44.  
  45. typedef enum {
  46.     RATE_ERRS = -1,
  47.     SILENCE,
  48.     RATE_QUANT,
  49.     RATE_QUARTER,
  50.     RATE_HALF,
  51.     RATE_FULL,
  52. } evrc_packet_rate;
  53.  
  54. /**
  55.  * EVRC-A unpacked data frame
  56.  */
  57. typedef struct EVRCAFrame {
  58.     uint8_t  lpc_flag;        ///< spectral change indicator
  59.     uint16_t lsp[4];          ///< index into LSP codebook
  60.     uint8_t  pitch_delay;     ///< pitch delay for entire frame
  61.     uint8_t  delay_diff;      ///< delay difference for entire frame
  62.     uint8_t  acb_gain[3];     ///< adaptive codebook gain
  63.     uint16_t fcb_shape[3][4]; ///< fixed codebook shape
  64.     uint8_t  fcb_gain[3];     ///< fixed codebook gain index
  65.     uint8_t  energy_gain;     ///< frame energy gain index
  66.     uint8_t  tty;             ///< tty baud rate bit
  67. } EVRCAFrame;
  68.  
  69. typedef struct EVRCContext {
  70.     AVClass *class;
  71.  
  72.     int              postfilter;
  73.  
  74.     GetBitContext    gb;
  75.     evrc_packet_rate bitrate;
  76.     evrc_packet_rate last_valid_bitrate;
  77.     EVRCAFrame       frame;
  78.  
  79.     float            lspf[FILTER_ORDER];
  80.     float            prev_lspf[FILTER_ORDER];
  81.     float            synthesis[FILTER_ORDER];
  82.     float            postfilter_fir[FILTER_ORDER];
  83.     float            postfilter_iir[FILTER_ORDER];
  84.     float            postfilter_residual[ACB_SIZE + SUBFRAME_SIZE];
  85.     float            pitch_delay;
  86.     float            prev_pitch_delay;
  87.     float            avg_acb_gain;  ///< average adaptive codebook gain
  88.     float            avg_fcb_gain;  ///< average fixed codebook gain
  89.     float            pitch[ACB_SIZE + FILTER_ORDER + SUBFRAME_SIZE];
  90.     float            pitch_back[ACB_SIZE];
  91.     float            interpolation_coeffs[136];
  92.     float            energy_vector[NB_SUBFRAMES];
  93.     float            fade_scale;
  94.     float            last;
  95.  
  96.     uint8_t          prev_energy_gain;
  97.     uint8_t          prev_error_flag;
  98.     uint8_t          warned_buf_mismatch_bitrate;
  99. } EVRCContext;
  100.  
  101. /**
  102.  * Frame unpacking for RATE_FULL, RATE_HALF and RATE_QUANT
  103.  *
  104.  * @param e the context
  105.  *
  106.  * TIA/IS-127 Table 4.21-1
  107.  */
  108. static void unpack_frame(EVRCContext *e)
  109. {
  110.     EVRCAFrame *frame = &e->frame;
  111.     GetBitContext *gb = &e->gb;
  112.  
  113.     switch (e->bitrate) {
  114.     case RATE_FULL:
  115.         frame->lpc_flag        = get_bits1(gb);
  116.         frame->lsp[0]          = get_bits(gb,  6);
  117.         frame->lsp[1]          = get_bits(gb,  6);
  118.         frame->lsp[2]          = get_bits(gb,  9);
  119.         frame->lsp[3]          = get_bits(gb,  7);
  120.         frame->pitch_delay     = get_bits(gb,  7);
  121.         frame->delay_diff      = get_bits(gb,  5);
  122.         frame->acb_gain[0]     = get_bits(gb,  3);
  123.         frame->fcb_shape[0][0] = get_bits(gb,  8);
  124.         frame->fcb_shape[0][1] = get_bits(gb,  8);
  125.         frame->fcb_shape[0][2] = get_bits(gb,  8);
  126.         frame->fcb_shape[0][3] = get_bits(gb, 11);
  127.         frame->fcb_gain[0]     = get_bits(gb,  5);
  128.         frame->acb_gain[1]     = get_bits(gb,  3);
  129.         frame->fcb_shape[1][0] = get_bits(gb,  8);
  130.         frame->fcb_shape[1][1] = get_bits(gb,  8);
  131.         frame->fcb_shape[1][2] = get_bits(gb,  8);
  132.         frame->fcb_shape[1][3] = get_bits(gb, 11);
  133.         frame->fcb_gain    [1] = get_bits(gb,  5);
  134.         frame->acb_gain    [2] = get_bits(gb,  3);
  135.         frame->fcb_shape[2][0] = get_bits(gb,  8);
  136.         frame->fcb_shape[2][1] = get_bits(gb,  8);
  137.         frame->fcb_shape[2][2] = get_bits(gb,  8);
  138.         frame->fcb_shape[2][3] = get_bits(gb, 11);
  139.         frame->fcb_gain    [2] = get_bits(gb,  5);
  140.         frame->tty             = get_bits1(gb);
  141.         break;
  142.     case RATE_HALF:
  143.         frame->lsp         [0] = get_bits(gb,  7);
  144.         frame->lsp         [1] = get_bits(gb,  7);
  145.         frame->lsp         [2] = get_bits(gb,  8);
  146.         frame->pitch_delay     = get_bits(gb,  7);
  147.         frame->acb_gain    [0] = get_bits(gb,  3);
  148.         frame->fcb_shape[0][0] = get_bits(gb, 10);
  149.         frame->fcb_gain    [0] = get_bits(gb,  4);
  150.         frame->acb_gain    [1] = get_bits(gb,  3);
  151.         frame->fcb_shape[1][0] = get_bits(gb, 10);
  152.         frame->fcb_gain    [1] = get_bits(gb,  4);
  153.         frame->acb_gain    [2] = get_bits(gb,  3);
  154.         frame->fcb_shape[2][0] = get_bits(gb, 10);
  155.         frame->fcb_gain    [2] = get_bits(gb,  4);
  156.         break;
  157.     case RATE_QUANT:
  158.         frame->lsp         [0] = get_bits(gb, 4);
  159.         frame->lsp         [1] = get_bits(gb, 4);
  160.         frame->energy_gain     = get_bits(gb, 8);
  161.         break;
  162.     }
  163. }
  164.  
  165. static evrc_packet_rate buf_size2bitrate(const int buf_size)
  166. {
  167.     switch (buf_size) {
  168.     case 23: return RATE_FULL;
  169.     case 11: return RATE_HALF;
  170.     case  6: return RATE_QUARTER;
  171.     case  3: return RATE_QUANT;
  172.     case  1: return SILENCE;
  173.     }
  174.  
  175.     return RATE_ERRS;
  176. }
  177.  
  178. /**
  179.  * Determine the bitrate from the frame size and/or the first byte of the frame.
  180.  *
  181.  * @param avctx the AV codec context
  182.  * @param buf_size length of the buffer
  183.  * @param buf the bufffer
  184.  *
  185.  * @return the bitrate on success,
  186.  *         RATE_ERRS  if the bitrate cannot be satisfactorily determined
  187.  */
  188. static evrc_packet_rate determine_bitrate(AVCodecContext *avctx,
  189.                                           int *buf_size,
  190.                                           const uint8_t **buf)
  191. {
  192.     evrc_packet_rate bitrate;
  193.  
  194.     if ((bitrate = buf_size2bitrate(*buf_size)) >= 0) {
  195.         if (bitrate > **buf) {
  196.             EVRCContext *e = avctx->priv_data;
  197.             if (!e->warned_buf_mismatch_bitrate) {
  198.                 av_log(avctx, AV_LOG_WARNING,
  199.                        "Claimed bitrate and buffer size mismatch.\n");
  200.                 e->warned_buf_mismatch_bitrate = 1;
  201.             }
  202.             bitrate = **buf;
  203.         } else if (bitrate < **buf) {
  204.             av_log(avctx, AV_LOG_ERROR,
  205.                    "Buffer is too small for the claimed bitrate.\n");
  206.             return RATE_ERRS;
  207.         }
  208.         (*buf)++;
  209.         *buf_size -= 1;
  210.     } else if ((bitrate = buf_size2bitrate(*buf_size + 1)) >= 0) {
  211.         av_log(avctx, AV_LOG_DEBUG,
  212.                "Bitrate byte is missing, guessing the bitrate from packet size.\n");
  213.     } else
  214.         return RATE_ERRS;
  215.  
  216.     return bitrate;
  217. }
  218.  
  219. static void warn_insufficient_frame_quality(AVCodecContext *avctx,
  220.                                             const char *message)
  221. {
  222.     av_log(avctx, AV_LOG_WARNING, "Frame #%d, %s\n",
  223.            avctx->frame_number, message);
  224. }
  225.  
  226. /**
  227.  * Initialize the speech codec according to the specification.
  228.  *
  229.  * TIA/IS-127 5.2
  230.  */
  231. static av_cold int evrc_decode_init(AVCodecContext *avctx)
  232. {
  233.     EVRCContext *e = avctx->priv_data;
  234.     int i, n, idx = 0;
  235.     float denom = 2.0 / (2.0 * 8.0 + 1.0);
  236.  
  237.     avctx->channels       = 1;
  238.     avctx->channel_layout = AV_CH_LAYOUT_MONO;
  239.     avctx->sample_fmt     = AV_SAMPLE_FMT_FLT;
  240.  
  241.     for (i = 0; i < FILTER_ORDER; i++) {
  242.         e->prev_lspf[i] = (i + 1) * 0.048;
  243.         e->synthesis[i] = 0.0;
  244.     }
  245.  
  246.     for (i = 0; i < ACB_SIZE; i++)
  247.         e->pitch[i] = e->pitch_back[i] = 0.0;
  248.  
  249.     e->last_valid_bitrate = RATE_QUANT;
  250.     e->prev_pitch_delay   = 40.0;
  251.     e->fade_scale         = 1.0;
  252.     e->prev_error_flag    = 0;
  253.     e->avg_acb_gain = e->avg_fcb_gain = 0.0;
  254.  
  255.     for (i = 0; i < 8; i++) {
  256.         float tt = ((float)i - 8.0 / 2.0) / 8.0;
  257.  
  258.         for (n = -8; n <= 8; n++, idx++) {
  259.             float arg1 = M_PI * 0.9 * (tt - n);
  260.             float arg2 = M_PI * (tt - n);
  261.  
  262.             e->interpolation_coeffs[idx] = 0.9;
  263.             if (arg1)
  264.                 e->interpolation_coeffs[idx] *= (0.54 + 0.46 * cos(arg2 * denom)) *
  265.                                                  sin(arg1) / arg1;
  266.         }
  267.     }
  268.  
  269.     return 0;
  270. }
  271.  
  272. /**
  273.  * Decode the 10 vector quantized line spectral pair frequencies from the LSP
  274.  * transmission codes of any bitrate and check for badly received packets.
  275.  *
  276.  * @param e the context
  277.  *
  278.  * @return 0 on success, -1 if the packet is badly received
  279.  *
  280.  * TIA/IS-127 5.2.1, 5.7.1
  281.  */
  282. static int decode_lspf(EVRCContext *e)
  283. {
  284.     const float * const *codebooks = evrc_lspq_codebooks[e->bitrate];
  285.     int i, j, k = 0;
  286.  
  287.     for (i = 0; i < evrc_lspq_nb_codebooks[e->bitrate]; i++) {
  288.         int row_size = evrc_lspq_codebooks_row_sizes[e->bitrate][i];
  289.         const float *codebook = codebooks[i];
  290.  
  291.         for (j = 0; j < row_size; j++)
  292.             e->lspf[k++] = codebook[e->frame.lsp[i] * row_size + j];
  293.     }
  294.  
  295.     // check for monotonic LSPs
  296.     for (i = 1; i < FILTER_ORDER; i++)
  297.         if (e->lspf[i] <= e->lspf[i - 1])
  298.             return -1;
  299.  
  300.     // check for minimum separation of LSPs at the splits
  301.     for (i = 0, k = 0; i < evrc_lspq_nb_codebooks[e->bitrate] - 1; i++) {
  302.         k += evrc_lspq_codebooks_row_sizes[e->bitrate][i];
  303.         if (e->lspf[k] - e->lspf[k - 1] <= MIN_LSP_SEP)
  304.             return -1;
  305.     }
  306.  
  307.     return 0;
  308. }
  309.  
  310. /*
  311.  * Interpolation of LSP parameters.
  312.  *
  313.  * TIA/IS-127 5.2.3.1, 5.7.3.2
  314.  */
  315. static void interpolate_lsp(float *ilsp, const float *lsp,
  316.                             const float *prev, int index)
  317. {
  318.     static const float lsp_interpolation_factors[] = { 0.1667, 0.5, 0.8333 };
  319.     ff_weighted_vector_sumf(ilsp, prev, lsp,
  320.                             1.0 - lsp_interpolation_factors[index],
  321.                             lsp_interpolation_factors[index], FILTER_ORDER);
  322. }
  323.  
  324. /*
  325.  * Reconstruction of the delay contour.
  326.  *
  327.  * TIA/IS-127 5.2.2.3.2
  328.  */
  329. static void interpolate_delay(float *dst, float current, float prev, int index)
  330. {
  331.     static const float d_interpolation_factors[] = { 0, 0.3313, 0.6625, 1, 1 };
  332.     dst[0] = (1.0 - d_interpolation_factors[index    ]) * prev
  333.                   + d_interpolation_factors[index    ]  * current;
  334.     dst[1] = (1.0 - d_interpolation_factors[index + 1]) * prev
  335.                   + d_interpolation_factors[index + 1]  * current;
  336.     dst[2] = (1.0 - d_interpolation_factors[index + 2]) * prev
  337.                   + d_interpolation_factors[index + 2]  * current;
  338. }
  339.  
  340. /*
  341.  * Convert the quantized, interpolated line spectral frequencies,
  342.  * to prediction coefficients.
  343.  *
  344.  * TIA/IS-127 5.2.3.2, 4.7.2.2
  345.  */
  346. static void decode_predictor_coeffs(const float *ilspf, float *ilpc)
  347. {
  348.     double lsp[FILTER_ORDER];
  349.     float a[FILTER_ORDER / 2 + 1], b[FILTER_ORDER / 2 + 1];
  350.     float a1[FILTER_ORDER / 2] = { 0 };
  351.     float a2[FILTER_ORDER / 2] = { 0 };
  352.     float b1[FILTER_ORDER / 2] = { 0 };
  353.     float b2[FILTER_ORDER / 2] = { 0 };
  354.     int i, k;
  355.  
  356.     ff_acelp_lsf2lspd(lsp, ilspf, FILTER_ORDER);
  357.  
  358.     for (k = 0; k <= FILTER_ORDER; k++) {
  359.         a[0] = k < 2 ? 0.25 : 0;
  360.         b[0] = k < 2 ? k < 1 ? 0.25 : -0.25 : 0;
  361.  
  362.         for (i = 0; i < FILTER_ORDER / 2; i++) {
  363.             a[i + 1] = a[i] - 2 * lsp[i * 2    ] * a1[i] + a2[i];
  364.             b[i + 1] = b[i] - 2 * lsp[i * 2 + 1] * b1[i] + b2[i];
  365.             a2[i] = a1[i];
  366.             a1[i] = a[i];
  367.             b2[i] = b1[i];
  368.             b1[i] = b[i];
  369.         }
  370.  
  371.         if (k)
  372.             ilpc[k - 1] = 2.0 * (a[FILTER_ORDER / 2] + b[FILTER_ORDER / 2]);
  373.     }
  374. }
  375.  
  376. static void bl_intrp(EVRCContext *e, float *ex, float delay)
  377. {
  378.     float *f;
  379.     int offset, i, coef_idx;
  380.     int16_t t;
  381.  
  382.     offset = lrintf(delay);
  383.  
  384.     t = (offset - delay + 0.5) * 8.0 + 0.5;
  385.     if (t == 8) {
  386.         t = 0;
  387.         offset--;
  388.     }
  389.  
  390.     f = ex - offset - 8;
  391.  
  392.     coef_idx = t * (2 * 8 + 1);
  393.  
  394.     ex[0] = 0.0;
  395.     for (i = 0; i < 2 * 8 + 1; i++)
  396.         ex[0] += e->interpolation_coeffs[coef_idx + i] * f[i];
  397. }
  398.  
  399. /*
  400.  * Adaptive codebook excitation.
  401.  *
  402.  * TIA/IS-127 5.2.2.3.3, 4.12.5.2
  403.  */
  404. static void acb_excitation(EVRCContext *e, float *excitation, float gain,
  405.                            const float delay[3], int length)
  406. {
  407.     float denom, locdelay, dpr, invl;
  408.     int i;
  409.  
  410.     invl = 1.0 / ((float) length);
  411.     dpr = length;
  412.  
  413.     /* first at-most extra samples */
  414.     denom = (delay[1] - delay[0]) * invl;
  415.     for (i = 0; i < dpr; i++) {
  416.         locdelay = delay[0] + i * denom;
  417.         bl_intrp(e, excitation + i, locdelay);
  418.     }
  419.  
  420.     denom = (delay[2] - delay[1]) * invl;
  421.     /* interpolation */
  422.     for (i = dpr; i < dpr + 10; i++) {
  423.         locdelay = delay[1] + (i - dpr) * denom;
  424.         bl_intrp(e, excitation + i, locdelay);
  425.     }
  426.  
  427.     for (i = 0; i < length; i++)
  428.         excitation[i] *= gain;
  429. }
  430.  
  431. static void decode_8_pulses_35bits(const uint16_t *fixed_index, float *cod)
  432. {
  433.     int i, pos1, pos2, offset;
  434.  
  435.     offset = (fixed_index[3] >> 9) & 3;
  436.  
  437.     for (i = 0; i < 3; i++) {
  438.         pos1 = ((fixed_index[i] & 0x7f) / 11) * 5 + ((i + offset) % 5);
  439.         pos2 = ((fixed_index[i] & 0x7f) % 11) * 5 + ((i + offset) % 5);
  440.  
  441.         cod[pos1] = (fixed_index[i] & 0x80) ? -1.0 : 1.0;
  442.  
  443.         if (pos2 < pos1)
  444.             cod[pos2]  = -cod[pos1];
  445.         else
  446.             cod[pos2] +=  cod[pos1];
  447.     }
  448.  
  449.     pos1 = ((fixed_index[3] & 0x7f) / 11) * 5 + ((3 + offset) % 5);
  450.     pos2 = ((fixed_index[3] & 0x7f) % 11) * 5 + ((4 + offset) % 5);
  451.  
  452.     cod[pos1] = (fixed_index[3] & 0x100) ? -1.0 : 1.0;
  453.     cod[pos2] = (fixed_index[3] & 0x80 ) ? -1.0 : 1.0;
  454. }
  455.  
  456. static void decode_3_pulses_10bits(uint16_t fixed_index, float *cod)
  457. {
  458.     float sign;
  459.     int pos;
  460.  
  461.     sign = (fixed_index & 0x200) ? -1.0 : 1.0;
  462.  
  463.     pos = ((fixed_index        & 0x7) * 7) + 4;
  464.     cod[pos] += sign;
  465.     pos = (((fixed_index >> 3) & 0x7) * 7) + 2;
  466.     cod[pos] -= sign;
  467.     pos = (((fixed_index >> 6) & 0x7) * 7);
  468.     cod[pos] += sign;
  469. }
  470.  
  471. /*
  472.  * Reconstruction of ACELP fixed codebook excitation for full and half rate.
  473.  *
  474.  * TIA/IS-127 5.2.3.7
  475.  */
  476. static void fcb_excitation(EVRCContext *e, const uint16_t *codebook,
  477.                            float *excitation, float pitch_gain,
  478.                            int pitch_lag, int subframe_size)
  479. {
  480.     int i;
  481.  
  482.     if (e->bitrate == RATE_FULL)
  483.         decode_8_pulses_35bits(codebook, excitation);
  484.     else
  485.         decode_3_pulses_10bits(*codebook, excitation);
  486.  
  487.     pitch_gain = av_clipf(pitch_gain, 0.2, 0.9);
  488.  
  489.     for (i = pitch_lag; i < subframe_size; i++)
  490.         excitation[i] += pitch_gain * excitation[i - pitch_lag];
  491. }
  492.  
  493. /**
  494.  * Synthesis of the decoder output signal.
  495.  *
  496.  * param[in]     in              input signal
  497.  * param[in]     filter_coeffs   LPC coefficients
  498.  * param[in/out] memory          synthesis filter memory
  499.  * param         buffer_length   amount of data to process
  500.  * param[out]    samples         output samples
  501.  *
  502.  * TIA/IS-127 5.2.3.15, 5.7.3.4
  503.  */
  504. static void synthesis_filter(const float *in, const float *filter_coeffs,
  505.                              float *memory, int buffer_length, float *samples)
  506. {
  507.     int i, j;
  508.  
  509.     for (i = 0; i < buffer_length; i++) {
  510.         samples[i] = in[i];
  511.         for (j = FILTER_ORDER - 1; j > 0; j--) {
  512.             samples[i] -= filter_coeffs[j] * memory[j];
  513.             memory[j]   = memory[j - 1];
  514.         }
  515.         samples[i] -= filter_coeffs[0] * memory[0];
  516.         memory[0]   = samples[i];
  517.     }
  518. }
  519.  
  520. static void bandwidth_expansion(float *coeff, const float *inbuf, float gamma)
  521. {
  522.     double fac = gamma;
  523.     int i;
  524.  
  525.     for (i = 0; i < FILTER_ORDER; i++) {
  526.         coeff[i] = inbuf[i] * fac;
  527.         fac *= gamma;
  528.     }
  529. }
  530.  
  531. static void residual_filter(float *output, const float *input,
  532.                             const float *coef, float *memory, int length)
  533. {
  534.     float sum;
  535.     int i, j;
  536.  
  537.     for (i = 0; i < length; i++) {
  538.         sum = input[i];
  539.  
  540.         for (j = FILTER_ORDER - 1; j > 0; j--) {
  541.             sum      += coef[j] * memory[j];
  542.             memory[j] = memory[j - 1];
  543.         }
  544.         sum += coef[0] * memory[0];
  545.         memory[0] = input[i];
  546.         output[i] = sum;
  547.     }
  548. }
  549.  
  550. /*
  551.  * TIA/IS-127 Table 5.9.1-1.
  552.  */
  553. static const struct PfCoeff {
  554.     float tilt;
  555.     float ltgain;
  556.     float p1;
  557.     float p2;
  558. } postfilter_coeffs[5] = {
  559.     { 0.0 , 0.0 , 0.0 , 0.0  },
  560.     { 0.0 , 0.0 , 0.57, 0.57 },
  561.     { 0.0 , 0.0 , 0.0 , 0.0  },
  562.     { 0.35, 0.50, 0.50, 0.75 },
  563.     { 0.20, 0.50, 0.57, 0.75 },
  564. };
  565.  
  566. /*
  567.  * Adaptive postfilter.
  568.  *
  569.  * TIA/IS-127 5.9
  570.  */
  571. static void postfilter(EVRCContext *e, float *in, const float *coeff,
  572.                        float *out, int idx, const struct PfCoeff *pfc,
  573.                        int length)
  574. {
  575.     float wcoef1[FILTER_ORDER], wcoef2[FILTER_ORDER],
  576.           scratch[SUBFRAME_SIZE], temp[SUBFRAME_SIZE],
  577.           mem[SUBFRAME_SIZE];
  578.     float sum1 = 0.0, sum2 = 0.0, gamma, gain;
  579.     float tilt = pfc->tilt;
  580.     int i, n, best;
  581.  
  582.     bandwidth_expansion(wcoef1, coeff, pfc->p1);
  583.     bandwidth_expansion(wcoef2, coeff, pfc->p2);
  584.  
  585.     /* Tilt compensation filter, TIA/IS-127 5.9.1 */
  586.     for (i = 0; i < length - 1; i++)
  587.         sum2 += in[i] * in[i + 1];
  588.     if (sum2 < 0.0)
  589.         tilt = 0.0;
  590.  
  591.     for (i = 0; i < length; i++) {
  592.         scratch[i] = in[i] - tilt * e->last;
  593.         e->last = in[i];
  594.     }
  595.  
  596.     /* Short term residual filter, TIA/IS-127 5.9.2 */
  597.     residual_filter(&e->postfilter_residual[ACB_SIZE], scratch, wcoef1, e->postfilter_fir, length);
  598.  
  599.     /* Long term postfilter */
  600.     best = idx;
  601.     for (i = FFMIN(MIN_DELAY, idx - 3); i <= FFMAX(MAX_DELAY, idx + 3); i++) {
  602.         for (n = ACB_SIZE, sum2 = 0; n < ACB_SIZE + length; n++)
  603.             sum2 += e->postfilter_residual[n] * e->postfilter_residual[n - i];
  604.         if (sum2 > sum1) {
  605.             sum1 = sum2;
  606.             best = i;
  607.         }
  608.     }
  609.  
  610.     for (i = ACB_SIZE, sum1 = 0; i < ACB_SIZE + length; i++)
  611.         sum1 += e->postfilter_residual[i - best] * e->postfilter_residual[i - best];
  612.     for (i = ACB_SIZE, sum2 = 0; i < ACB_SIZE + length; i++)
  613.         sum2 += e->postfilter_residual[i] * e->postfilter_residual[i - best];
  614.  
  615.     if (sum2 * sum1 == 0 || e->bitrate == RATE_QUANT) {
  616.         memcpy(temp, e->postfilter_residual + ACB_SIZE, length * sizeof(float));
  617.     } else {
  618.         gamma = sum2 / sum1;
  619.         if (gamma < 0.5)
  620.             memcpy(temp, e->postfilter_residual + ACB_SIZE, length * sizeof(float));
  621.         else {
  622.             gamma = FFMIN(gamma, 1.0);
  623.  
  624.             for (i = 0; i < length; i++) {
  625.                 temp[i] = e->postfilter_residual[ACB_SIZE + i] + gamma *
  626.                     pfc->ltgain * e->postfilter_residual[ACB_SIZE + i - best];
  627.             }
  628.         }
  629.     }
  630.  
  631.     memcpy(scratch, temp, length * sizeof(float));
  632.     memcpy(mem, e->postfilter_iir, FILTER_ORDER * sizeof(float));
  633.     synthesis_filter(scratch, wcoef2, mem, length, scratch);
  634.  
  635.     /* Gain computation, TIA/IS-127 5.9.4-2 */
  636.     for (i = 0, sum1 = 0, sum2 = 0; i < length; i++) {
  637.         sum1 += in[i] * in[i];
  638.         sum2 += scratch[i] * scratch[i];
  639.     }
  640.     gain = sum2 ? sqrt(sum1 / sum2) : 1.0;
  641.  
  642.     for (i = 0; i < length; i++)
  643.         temp[i] *= gain;
  644.  
  645.     /* Short term postfilter */
  646.     synthesis_filter(temp, wcoef2, e->postfilter_iir, length, out);
  647.  
  648.     memmove(e->postfilter_residual,
  649.            e->postfilter_residual + length, ACB_SIZE * sizeof(float));
  650. }
  651.  
  652. static void frame_erasure(EVRCContext *e, float *samples)
  653. {
  654.     float ilspf[FILTER_ORDER], ilpc[FILTER_ORDER], idelay[NB_SUBFRAMES],
  655.           tmp[SUBFRAME_SIZE + 6], f;
  656.     int i, j;
  657.  
  658.     for (i = 0; i < FILTER_ORDER; i++) {
  659.         if (e->bitrate != RATE_QUANT)
  660.             e->lspf[i] = e->prev_lspf[i] * 0.875 + 0.125 * (i + 1) * 0.048;
  661.         else
  662.             e->lspf[i] = e->prev_lspf[i];
  663.     }
  664.  
  665.     if (e->prev_error_flag)
  666.         e->avg_acb_gain *= 0.75;
  667.     if (e->bitrate == RATE_FULL)
  668.         memcpy(e->pitch_back, e->pitch, ACB_SIZE * sizeof(float));
  669.     if (e->last_valid_bitrate == RATE_QUANT)
  670.         e->bitrate = RATE_QUANT;
  671.     else
  672.         e->bitrate = RATE_FULL;
  673.  
  674.     if (e->bitrate == RATE_FULL || e->bitrate == RATE_HALF) {
  675.         e->pitch_delay = e->prev_pitch_delay;
  676.     } else {
  677.         float sum = 0;
  678.  
  679.         idelay[0] = idelay[1] = idelay[2] = MIN_DELAY;
  680.  
  681.         for (i = 0; i < NB_SUBFRAMES; i++)
  682.             sum += evrc_energy_quant[e->prev_energy_gain][i];
  683.         sum /= (float) NB_SUBFRAMES;
  684.         sum  = pow(10, sum);
  685.         for (i = 0; i < NB_SUBFRAMES; i++)
  686.             e->energy_vector[i] = sum;
  687.     }
  688.  
  689.     if (fabs(e->pitch_delay - e->prev_pitch_delay) > 15)
  690.         e->prev_pitch_delay = e->pitch_delay;
  691.  
  692.     for (i = 0; i < NB_SUBFRAMES; i++) {
  693.         int subframe_size = subframe_sizes[i];
  694.         int pitch_lag;
  695.  
  696.         interpolate_lsp(ilspf, e->lspf, e->prev_lspf, i);
  697.  
  698.         if (e->bitrate != RATE_QUANT) {
  699.             if (e->avg_acb_gain < 0.3) {
  700.                 idelay[0] = estimation_delay[i];
  701.                 idelay[1] = estimation_delay[i + 1];
  702.                 idelay[2] = estimation_delay[i + 2];
  703.             } else {
  704.                 interpolate_delay(idelay, e->pitch_delay, e->prev_pitch_delay, i);
  705.             }
  706.         }
  707.  
  708.         pitch_lag = lrintf((idelay[1] + idelay[0]) / 2.0);
  709.         decode_predictor_coeffs(ilspf, ilpc);
  710.  
  711.         if (e->bitrate != RATE_QUANT) {
  712.             acb_excitation(e, e->pitch + ACB_SIZE,
  713.                            e->avg_acb_gain, idelay, subframe_size);
  714.             for (j = 0; j < subframe_size; j++)
  715.                 e->pitch[ACB_SIZE + j] *= e->fade_scale;
  716.             e->fade_scale = FFMAX(e->fade_scale - 0.05, 0.0);
  717.         } else {
  718.             for (j = 0; j < subframe_size; j++)
  719.                 e->pitch[ACB_SIZE + j] = e->energy_vector[i];
  720.         }
  721.  
  722.         memmove(e->pitch, e->pitch + subframe_size, ACB_SIZE * sizeof(float));
  723.  
  724.         if (e->bitrate != RATE_QUANT && e->avg_acb_gain < 0.4) {
  725.             f = 0.1 * e->avg_fcb_gain;
  726.             for (j = 0; j < subframe_size; j++)
  727.                 e->pitch[ACB_SIZE + j] += f;
  728.         } else if (e->bitrate == RATE_QUANT) {
  729.             for (j = 0; j < subframe_size; j++)
  730.                 e->pitch[ACB_SIZE + j] = e->energy_vector[i];
  731.         }
  732.  
  733.         synthesis_filter(e->pitch + ACB_SIZE, ilpc,
  734.                          e->synthesis, subframe_size, tmp);
  735.         postfilter(e, tmp, ilpc, samples, pitch_lag,
  736.                    &postfilter_coeffs[e->bitrate], subframe_size);
  737.  
  738.         samples += subframe_size;
  739.     }
  740. }
  741.  
  742. static int evrc_decode_frame(AVCodecContext *avctx, void *data,
  743.                              int *got_frame_ptr, AVPacket *avpkt)
  744. {
  745.     const uint8_t *buf = avpkt->data;
  746.     AVFrame *frame     = data;
  747.     EVRCContext *e     = avctx->priv_data;
  748.     int buf_size       = avpkt->size;
  749.     float ilspf[FILTER_ORDER], ilpc[FILTER_ORDER], idelay[NB_SUBFRAMES];
  750.     float *samples;
  751.     int   i, j, ret, error_flag = 0;
  752.  
  753.     frame->nb_samples = 160;
  754.     if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
  755.         return ret;
  756.     samples = (float *)frame->data[0];
  757.  
  758.     if ((e->bitrate = determine_bitrate(avctx, &buf_size, &buf)) == RATE_ERRS) {
  759.         warn_insufficient_frame_quality(avctx, "bitrate cannot be determined.");
  760.         goto erasure;
  761.     }
  762.     if (e->bitrate <= SILENCE || e->bitrate == RATE_QUARTER)
  763.         goto erasure;
  764.     if (e->bitrate == RATE_QUANT && e->last_valid_bitrate == RATE_FULL
  765.                                  && !e->prev_error_flag)
  766.         goto erasure;
  767.  
  768.     if ((ret = init_get_bits8(&e->gb, buf, buf_size)) < 0)
  769.         return ret;
  770.     memset(&e->frame, 0, sizeof(EVRCAFrame));
  771.  
  772.     unpack_frame(e);
  773.  
  774.     if (e->bitrate != RATE_QUANT) {
  775.         uint8_t *p = (uint8_t *) &e->frame;
  776.         for (i = 0; i < sizeof(EVRCAFrame); i++) {
  777.             if (p[i])
  778.                 break;
  779.         }
  780.         if (i == sizeof(EVRCAFrame))
  781.             goto erasure;
  782.     } else if (e->frame.lsp[0] == 0xf &&
  783.                e->frame.lsp[1] == 0xf &&
  784.                e->frame.energy_gain == 0xff) {
  785.         goto erasure;
  786.     }
  787.  
  788.     if (decode_lspf(e) < 0)
  789.         goto erasure;
  790.  
  791.     if (e->bitrate == RATE_FULL || e->bitrate == RATE_HALF) {
  792.         /* Pitch delay parameter checking as per TIA/IS-127 5.1.5.1 */
  793.         if (e->frame.pitch_delay > MAX_DELAY - MIN_DELAY)
  794.             goto erasure;
  795.  
  796.         e->pitch_delay = e->frame.pitch_delay + MIN_DELAY;
  797.  
  798.         /* Delay diff parameter checking as per TIA/IS-127 5.1.5.2 */
  799.         if (e->frame.delay_diff) {
  800.             int p = e->pitch_delay - e->frame.delay_diff + 16;
  801.             if (p < MIN_DELAY || p > MAX_DELAY)
  802.                 goto erasure;
  803.         }
  804.  
  805.         /* Delay contour reconstruction as per TIA/IS-127 5.2.2.2 */
  806.         if (e->frame.delay_diff &&
  807.             e->bitrate == RATE_FULL && e->prev_error_flag) {
  808.             float delay;
  809.  
  810.             memcpy(e->pitch, e->pitch_back, ACB_SIZE * sizeof(float));
  811.  
  812.             delay = e->prev_pitch_delay;
  813.             e->prev_pitch_delay = delay - e->frame.delay_diff + 16.0;
  814.  
  815.             if (fabs(e->pitch_delay - delay) > 15)
  816.                 delay = e->pitch_delay;
  817.  
  818.             for (i = 0; i < NB_SUBFRAMES; i++) {
  819.                 int subframe_size = subframe_sizes[i];
  820.  
  821.                 interpolate_delay(idelay, delay, e->prev_pitch_delay, i);
  822.                 acb_excitation(e, e->pitch + ACB_SIZE, e->avg_acb_gain, idelay, subframe_size);
  823.                 memmove(e->pitch, e->pitch + subframe_size, ACB_SIZE * sizeof(float));
  824.             }
  825.         }
  826.  
  827.         /* Smoothing of the decoded delay as per TIA/IS-127 5.2.2.5 */
  828.         if (fabs(e->pitch_delay - e->prev_pitch_delay) > 15)
  829.             e->prev_pitch_delay = e->pitch_delay;
  830.  
  831.         e->avg_acb_gain = e->avg_fcb_gain = 0.0;
  832.     } else {
  833.         idelay[0] = idelay[1] = idelay[2] = MIN_DELAY;
  834.  
  835.         /* Decode frame energy vectors as per TIA/IS-127 5.7.2 */
  836.         for (i = 0; i < NB_SUBFRAMES; i++)
  837.             e->energy_vector[i] = pow(10, evrc_energy_quant[e->frame.energy_gain][i]);
  838.         e->prev_energy_gain = e->frame.energy_gain;
  839.     }
  840.  
  841.     for (i = 0; i < NB_SUBFRAMES; i++) {
  842.         float tmp[SUBFRAME_SIZE + 6] = { 0 };
  843.         int subframe_size = subframe_sizes[i];
  844.         int pitch_lag;
  845.  
  846.         interpolate_lsp(ilspf, e->lspf, e->prev_lspf, i);
  847.  
  848.         if (e->bitrate != RATE_QUANT)
  849.             interpolate_delay(idelay, e->pitch_delay, e->prev_pitch_delay, i);
  850.  
  851.         pitch_lag = lrintf((idelay[1] + idelay[0]) / 2.0);
  852.         decode_predictor_coeffs(ilspf, ilpc);
  853.  
  854.         /* Bandwidth expansion as per TIA/IS-127 5.2.3.3 */
  855.         if (e->frame.lpc_flag && e->prev_error_flag)
  856.             bandwidth_expansion(ilpc, ilpc, 0.75);
  857.  
  858.         if (e->bitrate != RATE_QUANT) {
  859.             float acb_sum, f;
  860.  
  861.             f = exp((e->bitrate == RATE_HALF ? 0.5 : 0.25)
  862.                          * (e->frame.fcb_gain[i] + 1));
  863.             acb_sum = pitch_gain_vq[e->frame.acb_gain[i]];
  864.             e->avg_acb_gain += acb_sum / NB_SUBFRAMES;
  865.             e->avg_fcb_gain += f / NB_SUBFRAMES;
  866.  
  867.             acb_excitation(e, e->pitch + ACB_SIZE,
  868.                            acb_sum, idelay, subframe_size);
  869.             fcb_excitation(e, e->frame.fcb_shape[i], tmp,
  870.                            acb_sum, pitch_lag, subframe_size);
  871.  
  872.             /* Total excitation generation as per TIA/IS-127 5.2.3.9 */
  873.             for (j = 0; j < subframe_size; j++)
  874.                 e->pitch[ACB_SIZE + j] += f * tmp[j];
  875.             e->fade_scale = FFMIN(e->fade_scale + 0.2, 1.0);
  876.         } else {
  877.             for (j = 0; j < subframe_size; j++)
  878.                 e->pitch[ACB_SIZE + j] = e->energy_vector[i];
  879.         }
  880.  
  881.         memmove(e->pitch, e->pitch + subframe_size, ACB_SIZE * sizeof(float));
  882.  
  883.         synthesis_filter(e->pitch + ACB_SIZE, ilpc,
  884.                          e->synthesis, subframe_size,
  885.                          e->postfilter ? tmp : samples);
  886.         if (e->postfilter)
  887.             postfilter(e, tmp, ilpc, samples, pitch_lag,
  888.                        &postfilter_coeffs[e->bitrate], subframe_size);
  889.  
  890.         samples += subframe_size;
  891.     }
  892.  
  893.     if (error_flag) {
  894. erasure:
  895.         error_flag = 1;
  896.         av_log(avctx, AV_LOG_WARNING, "frame erasure\n");
  897.         frame_erasure(e, samples);
  898.     }
  899.  
  900.     memcpy(e->prev_lspf, e->lspf, sizeof(e->prev_lspf));
  901.     e->prev_error_flag    = error_flag;
  902.     e->last_valid_bitrate = e->bitrate;
  903.  
  904.     if (e->bitrate != RATE_QUANT)
  905.         e->prev_pitch_delay = e->pitch_delay;
  906.  
  907.     samples = (float *)frame->data[0];
  908.     for (i = 0; i < 160; i++)
  909.         samples[i] /= 32768;
  910.  
  911.     *got_frame_ptr   = 1;
  912.  
  913.     return avpkt->size;
  914. }
  915.  
  916. #define OFFSET(x) offsetof(EVRCContext, x)
  917. #define AD AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_DECODING_PARAM
  918.  
  919. static const AVOption options[] = {
  920.     { "postfilter", "enable postfilter", OFFSET(postfilter), AV_OPT_TYPE_INT, {.i64 = 1}, 0, 1, AD },
  921.     { NULL }
  922. };
  923.  
  924. static const AVClass evrcdec_class = {
  925.     .class_name = "evrc",
  926.     .item_name  = av_default_item_name,
  927.     .option     = options,
  928.     .version    = LIBAVUTIL_VERSION_INT,
  929. };
  930.  
  931. AVCodec ff_evrc_decoder = {
  932.     .name           = "evrc",
  933.     .long_name      = NULL_IF_CONFIG_SMALL("EVRC (Enhanced Variable Rate Codec)"),
  934.     .type           = AVMEDIA_TYPE_AUDIO,
  935.     .id             = AV_CODEC_ID_EVRC,
  936.     .init           = evrc_decode_init,
  937.     .decode         = evrc_decode_frame,
  938.     .capabilities   = AV_CODEC_CAP_DR1,
  939.     .priv_data_size = sizeof(EVRCContext),
  940.     .priv_class     = &evrcdec_class,
  941. };
  942.