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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 "avcodec.h"
  30. #include "internal.h"
  31. #include "get_bits.h"
  32. #include "evrcdata.h"
  33. #include "acelp_vectors.h"
  34. #include "lsp.h"
  35.  
  36. #define MIN_LSP_SEP (0.05 / (2.0 * M_PI))
  37. #define MIN_DELAY      20
  38. #define MAX_DELAY     120
  39. #define NB_SUBFRAMES    3
  40. #define SUBFRAME_SIZE  54
  41. #define FILTER_ORDER   10
  42. #define ACB_SIZE      128
  43.  
  44. typedef enum {
  45.     RATE_ERRS = -1,
  46.     SILENCE,
  47.     RATE_QUANT,
  48.     RATE_QUARTER,
  49.     RATE_HALF,
  50.     RATE_FULL,
  51. } evrc_packet_rate;
  52.  
  53. /**
  54.  * EVRC-A unpacked data frame
  55.  */
  56. typedef struct EVRCAFrame {
  57.     uint8_t  lpc_flag;        ///< spectral change indicator
  58.     uint16_t lsp[4];          ///< index into LSP codebook
  59.     uint8_t  pitch_delay;     ///< pitch delay for entire frame
  60.     uint8_t  delay_diff;      ///< delay difference for entire frame
  61.     uint8_t  acb_gain[3];     ///< adaptive codebook gain
  62.     uint16_t fcb_shape[3][4]; ///< fixed codebook shape
  63.     uint8_t  fcb_gain[3];     ///< fixed codebook gain index
  64.     uint8_t  energy_gain;     ///< frame energy gain index
  65.     uint8_t  tty;             ///< tty baud rate bit
  66. } EVRCAFrame;
  67.  
  68. typedef struct EVRCContext {
  69.     GetBitContext    gb;
  70.     evrc_packet_rate bitrate;
  71.     evrc_packet_rate last_valid_bitrate;
  72.     EVRCAFrame       frame;
  73.  
  74.     float            lspf[FILTER_ORDER];
  75.     float            prev_lspf[FILTER_ORDER];
  76.     float            synthesis[FILTER_ORDER];
  77.     float            postfilter_fir[FILTER_ORDER];
  78.     float            postfilter_iir[FILTER_ORDER];
  79.     float            postfilter_residual[ACB_SIZE + SUBFRAME_SIZE];
  80.     float            pitch_delay;
  81.     float            prev_pitch_delay;
  82.     float            avg_acb_gain;  ///< average adaptive codebook gain
  83.     float            avg_fcb_gain;  ///< average fixed codebook gain
  84.     float            pitch[ACB_SIZE + FILTER_ORDER + SUBFRAME_SIZE];
  85.     float            pitch_back[ACB_SIZE];
  86.     float            interpolation_coeffs[136];
  87.     float            energy_vector[NB_SUBFRAMES];
  88.     float            fade_scale;
  89.     float            last;
  90.  
  91.     uint8_t          prev_energy_gain;
  92.     uint8_t          prev_error_flag;
  93.     uint8_t          warned_buf_mismatch_bitrate;
  94. } EVRCContext;
  95.  
  96. /**
  97.  * Frame unpacking for RATE_FULL, RATE_HALF and RATE_QUANT
  98.  *
  99.  * @param e the context
  100.  *
  101.  * TIA/IS-127 Table 4.21-1
  102.  */
  103. static void unpack_frame(EVRCContext *e)
  104. {
  105.     EVRCAFrame *frame = &e->frame;
  106.     GetBitContext *gb = &e->gb;
  107.  
  108.     switch (e->bitrate) {
  109.     case RATE_FULL:
  110.         frame->lpc_flag        = get_bits1(gb);
  111.         frame->lsp[0]          = get_bits(gb,  6);
  112.         frame->lsp[1]          = get_bits(gb,  6);
  113.         frame->lsp[2]          = get_bits(gb,  9);
  114.         frame->lsp[3]          = get_bits(gb,  7);
  115.         frame->pitch_delay     = get_bits(gb,  7);
  116.         frame->delay_diff      = get_bits(gb,  5);
  117.         frame->acb_gain[0]     = get_bits(gb,  3);
  118.         frame->fcb_shape[0][0] = get_bits(gb,  8);
  119.         frame->fcb_shape[0][1] = get_bits(gb,  8);
  120.         frame->fcb_shape[0][2] = get_bits(gb,  8);
  121.         frame->fcb_shape[0][3] = get_bits(gb, 11);
  122.         frame->fcb_gain[0]     = get_bits(gb,  5);
  123.         frame->acb_gain[1]     = get_bits(gb,  3);
  124.         frame->fcb_shape[1][0] = get_bits(gb,  8);
  125.         frame->fcb_shape[1][1] = get_bits(gb,  8);
  126.         frame->fcb_shape[1][2] = get_bits(gb,  8);
  127.         frame->fcb_shape[1][3] = get_bits(gb, 11);
  128.         frame->fcb_gain    [1] = get_bits(gb,  5);
  129.         frame->acb_gain    [2] = get_bits(gb,  3);
  130.         frame->fcb_shape[2][0] = get_bits(gb,  8);
  131.         frame->fcb_shape[2][1] = get_bits(gb,  8);
  132.         frame->fcb_shape[2][2] = get_bits(gb,  8);
  133.         frame->fcb_shape[2][3] = get_bits(gb, 11);
  134.         frame->fcb_gain    [2] = get_bits(gb,  5);
  135.         frame->tty             = get_bits1(gb);
  136.         break;
  137.     case RATE_HALF:
  138.         frame->lsp         [0] = get_bits(gb,  7);
  139.         frame->lsp         [1] = get_bits(gb,  7);
  140.         frame->lsp         [2] = get_bits(gb,  8);
  141.         frame->pitch_delay     = get_bits(gb,  7);
  142.         frame->acb_gain    [0] = get_bits(gb,  3);
  143.         frame->fcb_shape[0][0] = get_bits(gb, 10);
  144.         frame->fcb_gain    [0] = get_bits(gb,  4);
  145.         frame->acb_gain    [1] = get_bits(gb,  3);
  146.         frame->fcb_shape[1][0] = get_bits(gb, 10);
  147.         frame->fcb_gain    [1] = get_bits(gb,  4);
  148.         frame->acb_gain    [2] = get_bits(gb,  3);
  149.         frame->fcb_shape[2][0] = get_bits(gb, 10);
  150.         frame->fcb_gain    [2] = get_bits(gb,  4);
  151.         break;
  152.     case RATE_QUANT:
  153.         frame->lsp         [0] = get_bits(gb, 4);
  154.         frame->lsp         [1] = get_bits(gb, 4);
  155.         frame->energy_gain     = get_bits(gb, 8);
  156.         break;
  157.     }
  158. }
  159.  
  160. static evrc_packet_rate buf_size2bitrate(const int buf_size)
  161. {
  162.     switch (buf_size) {
  163.     case 23: return RATE_FULL;
  164.     case 11: return RATE_HALF;
  165.     case  6: return RATE_QUARTER;
  166.     case  3: return RATE_QUANT;
  167.     case  1: return SILENCE;
  168.     }
  169.  
  170.     return RATE_ERRS;
  171. }
  172.  
  173. /**
  174.  * Determine the bitrate from the frame size and/or the first byte of the frame.
  175.  *
  176.  * @param avctx the AV codec context
  177.  * @param buf_size length of the buffer
  178.  * @param buf the bufffer
  179.  *
  180.  * @return the bitrate on success,
  181.  *         RATE_ERRS  if the bitrate cannot be satisfactorily determined
  182.  */
  183. static evrc_packet_rate determine_bitrate(AVCodecContext *avctx,
  184.                                           int *buf_size,
  185.                                           const uint8_t **buf)
  186. {
  187.     evrc_packet_rate bitrate;
  188.  
  189.     if ((bitrate = buf_size2bitrate(*buf_size)) >= 0) {
  190.         if (bitrate > **buf) {
  191.             EVRCContext *e = avctx->priv_data;
  192.             if (!e->warned_buf_mismatch_bitrate) {
  193.                 av_log(avctx, AV_LOG_WARNING,
  194.                        "Claimed bitrate and buffer size mismatch.\n");
  195.                 e->warned_buf_mismatch_bitrate = 1;
  196.             }
  197.             bitrate = **buf;
  198.         } else if (bitrate < **buf) {
  199.             av_log(avctx, AV_LOG_ERROR,
  200.                    "Buffer is too small for the claimed bitrate.\n");
  201.             return RATE_ERRS;
  202.         }
  203.         (*buf)++;
  204.         *buf_size -= 1;
  205.     } else if ((bitrate = buf_size2bitrate(*buf_size + 1)) >= 0) {
  206.         av_log(avctx, AV_LOG_DEBUG,
  207.                "Bitrate byte is missing, guessing the bitrate from packet size.\n");
  208.     } else
  209.         return RATE_ERRS;
  210.  
  211.     return bitrate;
  212. }
  213.  
  214. static void warn_insufficient_frame_quality(AVCodecContext *avctx,
  215.                                             const char *message)
  216. {
  217.     av_log(avctx, AV_LOG_WARNING, "Frame #%d, %s\n",
  218.            avctx->frame_number, message);
  219. }
  220.  
  221. /**
  222.  * Initialize the speech codec according to the specification.
  223.  *
  224.  * TIA/IS-127 5.2
  225.  */
  226. static av_cold int evrc_decode_init(AVCodecContext *avctx)
  227. {
  228.     EVRCContext *e = avctx->priv_data;
  229.     int i, n, idx = 0;
  230.     float denom = 2.0 / (2.0 * 8.0 + 1.0);
  231.  
  232.     avctx->channels       = 1;
  233.     avctx->channel_layout = AV_CH_LAYOUT_MONO;
  234.     avctx->sample_fmt     = AV_SAMPLE_FMT_FLT;
  235.  
  236.     for (i = 0; i < FILTER_ORDER; i++) {
  237.         e->prev_lspf[i] = (i + 1) * 0.048;
  238.         e->synthesis[i] = 0.0;
  239.     }
  240.  
  241.     for (i = 0; i < ACB_SIZE; i++)
  242.         e->pitch[i] = e->pitch_back[i] = 0.0;
  243.  
  244.     e->last_valid_bitrate = RATE_QUANT;
  245.     e->prev_pitch_delay   = 40.0;
  246.     e->fade_scale         = 1.0;
  247.     e->prev_error_flag    = 0;
  248.     e->avg_acb_gain = e->avg_fcb_gain = 0.0;
  249.  
  250.     for (i = 0; i < 8; i++) {
  251.         float tt = ((float)i - 8.0 / 2.0) / 8.0;
  252.  
  253.         for (n = -8; n <= 8; n++, idx++) {
  254.             float arg1 = M_PI * 0.9 * (tt - n);
  255.             float arg2 = M_PI * (tt - n);
  256.  
  257.             e->interpolation_coeffs[idx] = 0.9;
  258.             if (arg1)
  259.                 e->interpolation_coeffs[idx] *= (0.54 + 0.46 * cos(arg2 * denom)) *
  260.                                                  sin(arg1) / arg1;
  261.         }
  262.     }
  263.  
  264.     return 0;
  265. }
  266.  
  267. /**
  268.  * Decode the 10 vector quantized line spectral pair frequencies from the LSP
  269.  * transmission codes of any bitrate and check for badly received packets.
  270.  *
  271.  * @param e the context
  272.  *
  273.  * @return 0 on success, -1 if the packet is badly received
  274.  *
  275.  * TIA/IS-127 5.2.1, 5.7.1
  276.  */
  277. static int decode_lspf(EVRCContext *e)
  278. {
  279.     const float **codebooks = evrc_lspq_codebooks[e->bitrate];
  280.     int i, j, k = 0;
  281.  
  282.     for (i = 0; i < evrc_lspq_nb_codebooks[e->bitrate]; i++) {
  283.         int row_size = evrc_lspq_codebooks_row_sizes[e->bitrate][i];
  284.         const float *codebook = codebooks[i];
  285.  
  286.         for (j = 0; j < row_size; j++)
  287.             e->lspf[k++] = codebook[e->frame.lsp[i] * row_size + j];
  288.     }
  289.  
  290.     // check for monotonic LSPs
  291.     for (i = 1; i < FILTER_ORDER; i++)
  292.         if (e->lspf[i] <= e->lspf[i - 1])
  293.             return -1;
  294.  
  295.     // check for minimum separation of LSPs at the splits
  296.     for (i = 0, k = 0; i < evrc_lspq_nb_codebooks[e->bitrate] - 1; i++) {
  297.         k += evrc_lspq_codebooks_row_sizes[e->bitrate][i];
  298.         if (e->lspf[k] - e->lspf[k - 1] <= MIN_LSP_SEP)
  299.             return -1;
  300.     }
  301.  
  302.     return 0;
  303. }
  304.  
  305. /*
  306.  * Interpolation of LSP parameters.
  307.  *
  308.  * TIA/IS-127 5.2.3.1, 5.7.3.2
  309.  */
  310. static void interpolate_lsp(float *ilsp, const float *lsp,
  311.                             const float *prev, int index)
  312. {
  313.     static const float lsp_interpolation_factors[] = { 0.1667, 0.5, 0.8333 };
  314.     ff_weighted_vector_sumf(ilsp, prev, lsp,
  315.                             1.0 - lsp_interpolation_factors[index],
  316.                             lsp_interpolation_factors[index], FILTER_ORDER);
  317. }
  318.  
  319. /*
  320.  * Reconstruction of the delay contour.
  321.  *
  322.  * TIA/IS-127 5.2.2.3.2
  323.  */
  324. static void interpolate_delay(float *dst, float current, float prev, int index)
  325. {
  326.     static const float d_interpolation_factors[] = { 0, 0.3313, 0.6625, 1, 1 };
  327.     dst[0] = (1.0 - d_interpolation_factors[index    ]) * prev
  328.                   + d_interpolation_factors[index    ]  * current;
  329.     dst[1] = (1.0 - d_interpolation_factors[index + 1]) * prev
  330.                   + d_interpolation_factors[index + 1]  * current;
  331.     dst[2] = (1.0 - d_interpolation_factors[index + 2]) * prev
  332.                   + d_interpolation_factors[index + 2]  * current;
  333. }
  334.  
  335. /*
  336.  * Convert the quantized, interpolated line spectral frequencies,
  337.  * to prediction coefficients.
  338.  *
  339.  * TIA/IS-127 5.2.3.2, 4.7.2.2
  340.  */
  341. static void decode_predictor_coeffs(const float *ilspf, float *ilpc)
  342. {
  343.     double lsp[FILTER_ORDER];
  344.     float a[FILTER_ORDER / 2 + 1], b[FILTER_ORDER / 2 + 1];
  345.     float a1[FILTER_ORDER / 2] = { 0 };
  346.     float a2[FILTER_ORDER / 2] = { 0 };
  347.     float b1[FILTER_ORDER / 2] = { 0 };
  348.     float b2[FILTER_ORDER / 2] = { 0 };
  349.     int i, k;
  350.  
  351.     ff_acelp_lsf2lspd(lsp, ilspf, FILTER_ORDER);
  352.  
  353.     for (k = 0; k <= FILTER_ORDER; k++) {
  354.         a[0] = k < 2 ? 0.25 : 0;
  355.         b[0] = k < 2 ? k < 1 ? 0.25 : -0.25 : 0;
  356.  
  357.         for (i = 0; i < FILTER_ORDER / 2; i++) {
  358.             a[i + 1] = a[i] - 2 * lsp[i * 2    ] * a1[i] + a2[i];
  359.             b[i + 1] = b[i] - 2 * lsp[i * 2 + 1] * b1[i] + b2[i];
  360.             a2[i] = a1[i];
  361.             a1[i] = a[i];
  362.             b2[i] = b1[i];
  363.             b1[i] = b[i];
  364.         }
  365.  
  366.         if (k)
  367.             ilpc[k - 1] = 2.0 * (a[FILTER_ORDER / 2] + b[FILTER_ORDER / 2]);
  368.     }
  369. }
  370.  
  371. static void bl_intrp(EVRCContext *e, float *ex, float delay)
  372. {
  373.     float *f;
  374.     int offset, i, coef_idx;
  375.     int16_t t;
  376.  
  377.     offset = lrintf(delay);
  378.  
  379.     t = (offset - delay + 0.5) * 8.0 + 0.5;
  380.     if (t == 8) {
  381.         t = 0;
  382.         offset--;
  383.     }
  384.  
  385.     f = ex - offset - 8;
  386.  
  387.     coef_idx = t * (2 * 8 + 1);
  388.  
  389.     ex[0] = 0.0;
  390.     for (i = 0; i < 2 * 8 + 1; i++)
  391.         ex[0] += e->interpolation_coeffs[coef_idx + i] * f[i];
  392. }
  393.  
  394. /*
  395.  * Adaptive codebook excitation.
  396.  *
  397.  * TIA/IS-127 5.2.2.3.3, 4.12.5.2
  398.  */
  399. static void acb_excitation(EVRCContext *e, float *excitation, float gain,
  400.                            const float delay[3], int length)
  401. {
  402.     float denom, locdelay, dpr, invl;
  403.     int i;
  404.  
  405.     invl = 1.0 / ((float) length);
  406.     dpr = length;
  407.  
  408.     /* first at-most extra samples */
  409.     denom = (delay[1] - delay[0]) * invl;
  410.     for (i = 0; i < dpr; i++) {
  411.         locdelay = delay[0] + i * denom;
  412.         bl_intrp(e, excitation + i, locdelay);
  413.     }
  414.  
  415.     denom = (delay[2] - delay[1]) * invl;
  416.     /* interpolation */
  417.     for (i = dpr; i < dpr + 10; i++) {
  418.         locdelay = delay[1] + (i - dpr) * denom;
  419.         bl_intrp(e, excitation + i, locdelay);
  420.     }
  421.  
  422.     for (i = 0; i < length; i++)
  423.         excitation[i] *= gain;
  424. }
  425.  
  426. static void decode_8_pulses_35bits(const uint16_t *fixed_index, float *cod)
  427. {
  428.     int i, pos1, pos2, offset;
  429.  
  430.     offset = (fixed_index[3] >> 9) & 3;
  431.  
  432.     for (i = 0; i < 3; i++) {
  433.         pos1 = ((fixed_index[i] & 0x7f) / 11) * 5 + ((i + offset) % 5);
  434.         pos2 = ((fixed_index[i] & 0x7f) % 11) * 5 + ((i + offset) % 5);
  435.  
  436.         cod[pos1] = (fixed_index[i] & 0x80) ? -1.0 : 1.0;
  437.  
  438.         if (pos2 < pos1)
  439.             cod[pos2]  = -cod[pos1];
  440.         else
  441.             cod[pos2] +=  cod[pos1];
  442.     }
  443.  
  444.     pos1 = ((fixed_index[3] & 0x7f) / 11) * 5 + ((3 + offset) % 5);
  445.     pos2 = ((fixed_index[3] & 0x7f) % 11) * 5 + ((4 + offset) % 5);
  446.  
  447.     cod[pos1] = (fixed_index[3] & 0x100) ? -1.0 : 1.0;
  448.     cod[pos2] = (fixed_index[3] & 0x80 ) ? -1.0 : 1.0;
  449. }
  450.  
  451. static void decode_3_pulses_10bits(uint16_t fixed_index, float *cod)
  452. {
  453.     float sign;
  454.     int pos;
  455.  
  456.     sign = (fixed_index & 0x200) ? -1.0 : 1.0;
  457.  
  458.     pos = ((fixed_index        & 0x7) * 7) + 4;
  459.     cod[pos] += sign;
  460.     pos = (((fixed_index >> 3) & 0x7) * 7) + 2;
  461.     cod[pos] -= sign;
  462.     pos = (((fixed_index >> 6) & 0x7) * 7);
  463.     cod[pos] += sign;
  464. }
  465.  
  466. /*
  467.  * Reconstruction of ACELP fixed codebook excitation for full and half rate.
  468.  *
  469.  * TIA/IS-127 5.2.3.7
  470.  */
  471. static void fcb_excitation(EVRCContext *e, const uint16_t *codebook,
  472.                            float *excitation, float pitch_gain,
  473.                            int pitch_lag, int subframe_size)
  474. {
  475.     int i;
  476.  
  477.     if (e->bitrate == RATE_FULL)
  478.         decode_8_pulses_35bits(codebook, excitation);
  479.     else
  480.         decode_3_pulses_10bits(*codebook, excitation);
  481.  
  482.     pitch_gain = av_clipf(pitch_gain, 0.2, 0.9);
  483.  
  484.     for (i = pitch_lag; i < subframe_size; i++)
  485.         excitation[i] += pitch_gain * excitation[i - pitch_lag];
  486. }
  487.  
  488. /**
  489.  * Synthesis of the decoder output signal.
  490.  *
  491.  * param[in]     in              input signal
  492.  * param[in]     filter_coeffs   LPC coefficients
  493.  * param[in/out] memory          synthesis filter memory
  494.  * param         buffer_length   amount of data to process
  495.  * param[out]    samples         output samples
  496.  *
  497.  * TIA/IS-127 5.2.3.15, 5.7.3.4
  498.  */
  499. static void synthesis_filter(const float *in, const float *filter_coeffs,
  500.                              float *memory, int buffer_length, float *samples)
  501. {
  502.     int i, j;
  503.  
  504.     for (i = 0; i < buffer_length; i++) {
  505.         samples[i] = in[i];
  506.         for (j = FILTER_ORDER - 1; j > 0; j--) {
  507.             samples[i] -= filter_coeffs[j] * memory[j];
  508.             memory[j]   = memory[j - 1];
  509.         }
  510.         samples[i] -= filter_coeffs[0] * memory[0];
  511.         memory[0]   = samples[i];
  512.     }
  513. }
  514.  
  515. static void bandwidth_expansion(float *coeff, const float *inbuf, float gamma)
  516. {
  517.     double fac = gamma;
  518.     int i;
  519.  
  520.     for (i = 0; i < FILTER_ORDER; i++) {
  521.         coeff[i] = inbuf[i] * fac;
  522.         fac *= gamma;
  523.     }
  524. }
  525.  
  526. static void residual_filter(float *output, const float *input,
  527.                             const float *coef, float *memory, int length)
  528. {
  529.     float sum;
  530.     int i, j;
  531.  
  532.     for (i = 0; i < length; i++) {
  533.         sum = input[i];
  534.  
  535.         for (j = FILTER_ORDER - 1; j > 0; j--) {
  536.             sum      += coef[j] * memory[j];
  537.             memory[j] = memory[j - 1];
  538.         }
  539.         sum += coef[0] * memory[0];
  540.         memory[0] = input[i];
  541.         output[i] = sum;
  542.     }
  543. }
  544.  
  545. /*
  546.  * TIA/IS-127 Table 5.9.1-1.
  547.  */
  548. static const struct PfCoeff {
  549.     float tilt;
  550.     float ltgain;
  551.     float p1;
  552.     float p2;
  553. } postfilter_coeffs[5] = {
  554.     { 0.0 , 0.0 , 0.0 , 0.0  },
  555.     { 0.0 , 0.0 , 0.57, 0.57 },
  556.     { 0.0 , 0.0 , 0.0 , 0.0  },
  557.     { 0.35, 0.50, 0.50, 0.75 },
  558.     { 0.20, 0.50, 0.57, 0.75 },
  559. };
  560.  
  561. /*
  562.  * Adaptive postfilter.
  563.  *
  564.  * TIA/IS-127 5.9
  565.  */
  566. static void postfilter(EVRCContext *e, float *in, const float *coeff,
  567.                        float *out, int idx, const struct PfCoeff *pfc,
  568.                        int length)
  569. {
  570.     float wcoef1[FILTER_ORDER], wcoef2[FILTER_ORDER],
  571.           scratch[SUBFRAME_SIZE], temp[SUBFRAME_SIZE],
  572.           mem[SUBFRAME_SIZE];
  573.     float sum1 = 0.0, sum2 = 0.0, gamma, gain;
  574.     float tilt = pfc->tilt;
  575.     int i, n, best;
  576.  
  577.     bandwidth_expansion(wcoef1, coeff, pfc->p1);
  578.     bandwidth_expansion(wcoef2, coeff, pfc->p2);
  579.  
  580.     /* Tilt compensation filter, TIA/IS-127 5.9.1 */
  581.     for (i = 0; i < length - 1; i++)
  582.         sum2 += in[i] * in[i + 1];
  583.     if (sum2 < 0.0)
  584.         tilt = 0.0;
  585.  
  586.     for (i = 0; i < length; i++) {
  587.         scratch[i] = in[i] - tilt * e->last;
  588.         e->last = in[i];
  589.     }
  590.  
  591.     /* Short term residual filter, TIA/IS-127 5.9.2 */
  592.     residual_filter(&e->postfilter_residual[ACB_SIZE], scratch, wcoef1, e->postfilter_fir, length);
  593.  
  594.     /* Long term postfilter */
  595.     best = idx;
  596.     for (i = FFMIN(MIN_DELAY, idx - 3); i <= FFMAX(MAX_DELAY, idx + 3); i++) {
  597.         for (n = ACB_SIZE, sum2 = 0; n < ACB_SIZE + length; n++)
  598.             sum2 += e->postfilter_residual[n] * e->postfilter_residual[n - i];
  599.         if (sum2 > sum1) {
  600.             sum1 = sum2;
  601.             best = i;
  602.         }
  603.     }
  604.  
  605.     for (i = ACB_SIZE, sum1 = 0; i < ACB_SIZE + length; i++)
  606.         sum1 += e->postfilter_residual[i - best] * e->postfilter_residual[i - best];
  607.     for (i = ACB_SIZE, sum2 = 0; i < ACB_SIZE + length; i++)
  608.         sum2 += e->postfilter_residual[i] * e->postfilter_residual[i - best];
  609.  
  610.     if (sum2 * sum1 == 0 || e->bitrate == RATE_QUANT) {
  611.         memcpy(temp, e->postfilter_residual + ACB_SIZE, length * sizeof(float));
  612.     } else {
  613.         gamma = sum2 / sum1;
  614.         if (gamma < 0.5)
  615.             memcpy(temp, e->postfilter_residual + ACB_SIZE, length * sizeof(float));
  616.         else {
  617.             gamma = FFMIN(gamma, 1.0);
  618.  
  619.             for (i = 0; i < length; i++) {
  620.                 temp[i] = e->postfilter_residual[ACB_SIZE + i] + gamma *
  621.                     pfc->ltgain * e->postfilter_residual[ACB_SIZE + i - best];
  622.             }
  623.         }
  624.     }
  625.  
  626.     memcpy(scratch, temp, length * sizeof(float));
  627.     memcpy(mem, e->postfilter_iir, FILTER_ORDER * sizeof(float));
  628.     synthesis_filter(scratch, wcoef2, mem, length, scratch);
  629.  
  630.     /* Gain computation, TIA/IS-127 5.9.4-2 */
  631.     for (i = 0, sum1 = 0, sum2 = 0; i < length; i++) {
  632.         sum1 += in[i] * in[i];
  633.         sum2 += scratch[i] * scratch[i];
  634.     }
  635.     gain = sum2 ? sqrt(sum1 / sum2) : 1.0;
  636.  
  637.     for (i = 0; i < length; i++)
  638.         temp[i] *= gain;
  639.  
  640.     /* Short term postfilter */
  641.     synthesis_filter(temp, wcoef2, e->postfilter_iir, length, out);
  642.  
  643.     memmove(e->postfilter_residual,
  644.            e->postfilter_residual + length, ACB_SIZE * sizeof(float));
  645. }
  646.  
  647. static void frame_erasure(EVRCContext *e, float *samples)
  648. {
  649.     float ilspf[FILTER_ORDER], ilpc[FILTER_ORDER], idelay[NB_SUBFRAMES],
  650.           tmp[SUBFRAME_SIZE + 6], f;
  651.     int i, j;
  652.  
  653.     for (i = 0; i < FILTER_ORDER; i++) {
  654.         if (e->bitrate != RATE_QUANT)
  655.             e->lspf[i] = e->prev_lspf[i] * 0.875 + 0.125 * (i + 1) * 0.048;
  656.         else
  657.             e->lspf[i] = e->prev_lspf[i];
  658.     }
  659.  
  660.     if (e->prev_error_flag)
  661.         e->avg_acb_gain *= 0.75;
  662.     if (e->bitrate == RATE_FULL)
  663.         memcpy(e->pitch_back, e->pitch, ACB_SIZE * sizeof(float));
  664.     if (e->last_valid_bitrate == RATE_QUANT)
  665.         e->bitrate = RATE_QUANT;
  666.     else
  667.         e->bitrate = RATE_FULL;
  668.  
  669.     if (e->bitrate == RATE_FULL || e->bitrate == RATE_HALF) {
  670.         e->pitch_delay = e->prev_pitch_delay;
  671.     } else {
  672.         float sum = 0;
  673.  
  674.         idelay[0] = idelay[1] = idelay[2] = MIN_DELAY;
  675.  
  676.         for (i = 0; i < NB_SUBFRAMES; i++)
  677.             sum += evrc_energy_quant[e->prev_energy_gain][i];
  678.         sum /= (float) NB_SUBFRAMES;
  679.         sum  = pow(10, sum);
  680.         for (i = 0; i < NB_SUBFRAMES; i++)
  681.             e->energy_vector[i] = sum;
  682.     }
  683.  
  684.     if (fabs(e->pitch_delay - e->prev_pitch_delay) > 15)
  685.         e->prev_pitch_delay = e->pitch_delay;
  686.  
  687.     for (i = 0; i < NB_SUBFRAMES; i++) {
  688.         int subframe_size = subframe_sizes[i];
  689.         int pitch_lag;
  690.  
  691.         interpolate_lsp(ilspf, e->lspf, e->prev_lspf, i);
  692.  
  693.         if (e->bitrate != RATE_QUANT) {
  694.             if (e->avg_acb_gain < 0.3) {
  695.                 idelay[0] = estimation_delay[i];
  696.                 idelay[1] = estimation_delay[i + 1];
  697.                 idelay[2] = estimation_delay[i + 2];
  698.             } else {
  699.                 interpolate_delay(idelay, e->pitch_delay, e->prev_pitch_delay, i);
  700.             }
  701.         }
  702.  
  703.         pitch_lag = lrintf((idelay[1] + idelay[0]) / 2.0);
  704.         decode_predictor_coeffs(ilspf, ilpc);
  705.  
  706.         if (e->bitrate != RATE_QUANT) {
  707.             acb_excitation(e, e->pitch + ACB_SIZE,
  708.                            e->avg_acb_gain, idelay, subframe_size);
  709.             for (j = 0; j < subframe_size; j++)
  710.                 e->pitch[ACB_SIZE + j] *= e->fade_scale;
  711.             e->fade_scale = FFMAX(e->fade_scale - 0.05, 0.0);
  712.         } else {
  713.             for (j = 0; j < subframe_size; j++)
  714.                 e->pitch[ACB_SIZE + j] = e->energy_vector[i];
  715.         }
  716.  
  717.         memmove(e->pitch, e->pitch + subframe_size, ACB_SIZE * sizeof(float));
  718.  
  719.         if (e->bitrate != RATE_QUANT && e->avg_acb_gain < 0.4) {
  720.             f = 0.1 * e->avg_fcb_gain;
  721.             for (j = 0; j < subframe_size; j++)
  722.                 e->pitch[ACB_SIZE + j] += f;
  723.         } else if (e->bitrate == RATE_QUANT) {
  724.             for (j = 0; j < subframe_size; j++)
  725.                 e->pitch[ACB_SIZE + j] = e->energy_vector[i];
  726.         }
  727.  
  728.         synthesis_filter(e->pitch + ACB_SIZE, ilpc,
  729.                          e->synthesis, subframe_size, tmp);
  730.         postfilter(e, tmp, ilpc, samples, pitch_lag,
  731.                    &postfilter_coeffs[e->bitrate], subframe_size);
  732.  
  733.         samples += subframe_size;
  734.     }
  735. }
  736.  
  737. static int evrc_decode_frame(AVCodecContext *avctx, void *data,
  738.                              int *got_frame_ptr, AVPacket *avpkt)
  739. {
  740.     const uint8_t *buf = avpkt->data;
  741.     AVFrame *frame     = data;
  742.     EVRCContext *e     = avctx->priv_data;
  743.     int buf_size       = avpkt->size;
  744.     float ilspf[FILTER_ORDER], ilpc[FILTER_ORDER], idelay[NB_SUBFRAMES];
  745.     float *samples;
  746.     int   i, j, ret, error_flag = 0;
  747.  
  748.     frame->nb_samples = 160;
  749.     if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
  750.         return ret;
  751.     samples = (float *)frame->data[0];
  752.  
  753.     if ((e->bitrate = determine_bitrate(avctx, &buf_size, &buf)) == RATE_ERRS) {
  754.         warn_insufficient_frame_quality(avctx, "bitrate cannot be determined.");
  755.         goto erasure;
  756.     }
  757.     if (e->bitrate <= SILENCE || e->bitrate == RATE_QUARTER)
  758.         goto erasure;
  759.     if (e->bitrate == RATE_QUANT && e->last_valid_bitrate == RATE_FULL
  760.                                  && !e->prev_error_flag)
  761.         goto erasure;
  762.  
  763.     init_get_bits(&e->gb, buf, 8 * buf_size);
  764.     memset(&e->frame, 0, sizeof(EVRCAFrame));
  765.  
  766.     unpack_frame(e);
  767.  
  768.     if (e->bitrate != RATE_QUANT) {
  769.         uint8_t *p = (uint8_t *) &e->frame;
  770.         for (i = 0; i < sizeof(EVRCAFrame); i++) {
  771.             if (p[i])
  772.                 break;
  773.         }
  774.         if (i == sizeof(EVRCAFrame))
  775.             goto erasure;
  776.     } else if (e->frame.lsp[0] == 0xf &&
  777.                e->frame.lsp[1] == 0xf &&
  778.                e->frame.energy_gain == 0xff) {
  779.         goto erasure;
  780.     }
  781.  
  782.     if (decode_lspf(e) < 0)
  783.         goto erasure;
  784.  
  785.     if (e->bitrate == RATE_FULL || e->bitrate == RATE_HALF) {
  786.         /* Pitch delay parameter checking as per TIA/IS-127 5.1.5.1 */
  787.         if (e->frame.pitch_delay > MAX_DELAY - MIN_DELAY)
  788.             goto erasure;
  789.  
  790.         e->pitch_delay = e->frame.pitch_delay + MIN_DELAY;
  791.  
  792.         /* Delay diff parameter checking as per TIA/IS-127 5.1.5.2 */
  793.         if (e->frame.delay_diff) {
  794.             int p = e->pitch_delay - e->frame.delay_diff + 16;
  795.             if (p < MIN_DELAY || p > MAX_DELAY)
  796.                 goto erasure;
  797.         }
  798.  
  799.         /* Delay contour reconstruction as per TIA/IS-127 5.2.2.2 */
  800.         if (e->frame.delay_diff &&
  801.             e->bitrate == RATE_FULL && e->prev_error_flag) {
  802.             float delay;
  803.  
  804.             memcpy(e->pitch, e->pitch_back, ACB_SIZE * sizeof(float));
  805.  
  806.             delay = e->prev_pitch_delay;
  807.             e->prev_pitch_delay = delay - e->frame.delay_diff + 16.0;
  808.  
  809.             if (fabs(e->pitch_delay - delay) > 15)
  810.                 delay = e->pitch_delay;
  811.  
  812.             for (i = 0; i < NB_SUBFRAMES; i++) {
  813.                 int subframe_size = subframe_sizes[i];
  814.  
  815.                 interpolate_delay(idelay, delay, e->prev_pitch_delay, i);
  816.                 acb_excitation(e, e->pitch + ACB_SIZE, e->avg_acb_gain, idelay, subframe_size);
  817.                 memmove(e->pitch, e->pitch + subframe_size, ACB_SIZE * sizeof(float));
  818.             }
  819.         }
  820.  
  821.         /* Smoothing of the decoded delay as per TIA/IS-127 5.2.2.5 */
  822.         if (fabs(e->pitch_delay - e->prev_pitch_delay) > 15)
  823.             e->prev_pitch_delay = e->pitch_delay;
  824.  
  825.         e->avg_acb_gain = e->avg_fcb_gain = 0.0;
  826.     } else {
  827.         idelay[0] = idelay[1] = idelay[2] = MIN_DELAY;
  828.  
  829.         /* Decode frame energy vectors as per TIA/IS-127 5.7.2 */
  830.         for (i = 0; i < NB_SUBFRAMES; i++)
  831.             e->energy_vector[i] = pow(10, evrc_energy_quant[e->frame.energy_gain][i]);
  832.         e->prev_energy_gain = e->frame.energy_gain;
  833.     }
  834.  
  835.     for (i = 0; i < NB_SUBFRAMES; i++) {
  836.         float tmp[SUBFRAME_SIZE + 6] = { 0 };
  837.         int subframe_size = subframe_sizes[i];
  838.         int pitch_lag;
  839.  
  840.         interpolate_lsp(ilspf, e->lspf, e->prev_lspf, i);
  841.  
  842.         if (e->bitrate != RATE_QUANT)
  843.             interpolate_delay(idelay, e->pitch_delay, e->prev_pitch_delay, i);
  844.  
  845.         pitch_lag = lrintf((idelay[1] + idelay[0]) / 2.0);
  846.         decode_predictor_coeffs(ilspf, ilpc);
  847.  
  848.         /* Bandwidth expansion as per TIA/IS-127 5.2.3.3 */
  849.         if (e->frame.lpc_flag && e->prev_error_flag)
  850.             bandwidth_expansion(ilpc, ilpc, 0.75);
  851.  
  852.         if (e->bitrate != RATE_QUANT) {
  853.             float acb_sum, f;
  854.  
  855.             f = exp((e->bitrate == RATE_HALF ? 0.5 : 0.25)
  856.                          * (e->frame.fcb_gain[i] + 1));
  857.             acb_sum = pitch_gain_vq[e->frame.acb_gain[i]];
  858.             e->avg_acb_gain += acb_sum / NB_SUBFRAMES;
  859.             e->avg_fcb_gain += f / NB_SUBFRAMES;
  860.  
  861.             acb_excitation(e, e->pitch + ACB_SIZE,
  862.                            acb_sum, idelay, subframe_size);
  863.             fcb_excitation(e, e->frame.fcb_shape[i], tmp,
  864.                            acb_sum, pitch_lag, subframe_size);
  865.  
  866.             /* Total excitation generation as per TIA/IS-127 5.2.3.9 */
  867.             for (j = 0; j < subframe_size; j++)
  868.                 e->pitch[ACB_SIZE + j] += f * tmp[j];
  869.             e->fade_scale = FFMIN(e->fade_scale + 0.2, 1.0);
  870.         } else {
  871.             for (j = 0; j < subframe_size; j++)
  872.                 e->pitch[ACB_SIZE + j] = e->energy_vector[i];
  873.         }
  874.  
  875.         memmove(e->pitch, e->pitch + subframe_size, ACB_SIZE * sizeof(float));
  876.  
  877.         synthesis_filter(e->pitch + ACB_SIZE, ilpc,
  878.                          e->synthesis, subframe_size, tmp);
  879.         postfilter(e, tmp, ilpc, samples, pitch_lag,
  880.                    &postfilter_coeffs[e->bitrate], subframe_size);
  881.  
  882.         samples += subframe_size;
  883.     }
  884.  
  885.     if (error_flag) {
  886. erasure:
  887.         error_flag = 1;
  888.         av_log(avctx, AV_LOG_WARNING, "frame erasure\n");
  889.         frame_erasure(e, samples);
  890.     }
  891.  
  892.     memcpy(e->prev_lspf, e->lspf, sizeof(e->prev_lspf));
  893.     e->prev_error_flag    = error_flag;
  894.     e->last_valid_bitrate = e->bitrate;
  895.  
  896.     if (e->bitrate != RATE_QUANT)
  897.         e->prev_pitch_delay = e->pitch_delay;
  898.  
  899.     samples = (float *)frame->data[0];
  900.     for (i = 0; i < 160; i++)
  901.         samples[i] /= 32768;
  902.  
  903.     *got_frame_ptr   = 1;
  904.  
  905.     return avpkt->size;
  906. }
  907.  
  908. AVCodec ff_evrc_decoder = {
  909.     .name           = "evrc",
  910.     .long_name      = NULL_IF_CONFIG_SMALL("EVRC (Enhanced Variable Rate Codec)"),
  911.     .type           = AVMEDIA_TYPE_AUDIO,
  912.     .id             = AV_CODEC_ID_EVRC,
  913.     .init           = evrc_decode_init,
  914.     .decode         = evrc_decode_frame,
  915.     .capabilities   = CODEC_CAP_DR1,
  916.     .priv_data_size = sizeof(EVRCContext),
  917. };
  918.