コード例 #1
0
ファイル: enc_main.c プロジェクト: shima-park/asr
/*
 * E_MAIN_init
 *
 * Parameters:
 *    spe_state         I/O: pointer to state structure
 *
 * Function:
 *    Initialisation of variables for the coder section.
 *    Memory allocation.
 *
 * Returns:
 *    void
 */
Word16 E_MAIN_init(void **spe_state)
{
   Coder_State *st;
   *spe_state = NULL;
   /* allocate memory */
   if ((st = (Coder_State *) malloc(sizeof(Coder_State))) == NULL)
   {
      return(-1);
   }
   st->vadSt = NULL;
   st->dtx_encSt = NULL;
   E_DTX_init(&(st->dtx_encSt));
   E_DTX_vad_init(&(st->vadSt));
   E_MAIN_reset((void *) st, 1);
   *spe_state = (void*)st;
   return(0);
}
コード例 #2
0
ファイル: enc_main.c プロジェクト: shima-park/asr
/*
 * E_MAIN_encode
 *
 * Parameters:
 *    mode        I: used mode
 *    input_sp    I: 320 new speech samples (at 16 kHz)
 *    prms        O: output parameters
 *    spe_state   B: state structure
 *    allow_dtx   I: DTX ON/OFF
 *
 * Function:
 *    Main coder routine.
 *
 * Returns:
 *    void
 */
Word16 E_MAIN_encode(Word16 * mode, Word16 speech16k[], Word16 prms[],
                    void *spe_state, Word16 allow_dtx)
{
   /* Float32 */
   Float32 f_speech16k[L_FRAME16k];    /* Speech vector                          */
   Float32 f_old_exc[(L_FRAME + 1) + PIT_MAX + L_INTERPOL]; /* Excitation vector */
   Float32 f_exc2[L_FRAME];            /* excitation vector                      */
   Float32 error[M + L_SUBFR];         /* error of quantization                  */
   Float32 A[NB_SUBFR * (M + 1)];      /* A(z) unquantized for the 4 subframes   */
   Float32 Aq[NB_SUBFR * (M + 1)];     /* A(z)   quantized for the 4 subframes   */
   Float32 xn[L_SUBFR];                /* Target vector for pitch search         */
   Float32 xn2[L_SUBFR];               /* Target vector for codebook search      */
   Float32 dn[L_SUBFR];                /* Correlation between xn2 and h1         */
   Float32 cn[L_SUBFR];                /* Target vector in residual domain       */
   Float32 h1[L_SUBFR];                /* Impulse response vector                */
   Float32 f_code[L_SUBFR];            /* Fixed codebook excitation              */
   Float32 y1[L_SUBFR];                /* Filtered adaptive excitation           */
   Float32 y2[L_SUBFR];                /* Filtered adaptive excitation           */
   Float32 synth[L_SUBFR];             /* 12.8kHz synthesis vector               */
   Float32 r[M + 1];                   /* Autocorrelations of windowed speech    */
   Float32 Ap[M + 1];                  /* A(z) with spectral expansion           */
   Float32 ispnew[M];                  /* immittance spectral pairs at 4nd sfr   */
   Float32 isf[M];                     /* ISF (frequency domain) at 4nd sfr      */
   Float32 g_coeff[5], g_coeff2[2];    /* Correlations                           */
   Float32 gain_pit;
   Float32 f_tmp, gain1, gain2;
   Float32 stab_fac = 0.0F, fac;
   Float32 *new_speech, *speech;       /* Speech vector                          */
   Float32 *wsp;                       /* Weighted speech vector                 */
   Float32 *f_exc;                     /* Excitation vector                      */
   Float32 *p_A, *p_Aq;                /* ptr to A(z) for the 4 subframes        */
   Float32 *f_pt_tmp;
   /* Word32 */
   Word32 indice[8];                   /* quantization indices                   */
   Word32 vad_flag, clip_gain;
   Word32 T_op, T_op2, T0, T0_frac;
   Word32 T0_min, T0_max;
   Word32 voice_fac, Q_new = 0;
   Word32 L_gain_code, l_tmp;
   Word32 i, i_subfr, pit_flag;
   /* Word16 */
   Word16 exc2[L_FRAME];               /* excitation vector                      */
   Word16 s_Aq[NB_SUBFR * (M + 1)];    /* A(z) quantized for the 4 subframes     */
   Word16 s_code[L_SUBFR];             /* Fixed codebook excitation              */
   Word16 ispnew_q[M];                 /* quantized ISPs at 4nd subframe         */
   Word16 isfq[M];                     /* quantized ISPs                         */
   Word16 select, codec_mode;
   Word16 index;
   Word16 s_gain_pit, gain_code;
   Word16 s_tmp, s_max;
   Word16 corr_gain;
   Word16 *exc;                        /* Excitation vector                      */
   /* Other */
   Coder_State *st;                    /* Coder states                           */
   /* Memory Usage eval */
   st = (Coder_State *)spe_state;
   codec_mode = *mode;
   /*
    * Initialize pointers to speech vector.
    *
    *
    *         |-------|-------|-------|-------|-------|-------|
    *          past sp   sf1     sf2     sf3     sf4    L_NEXT
    *         <-------  Total speech buffer (L_TOTAL)   ------>
    *   old_speech
    *         <-------  LPC analysis window (L_WINDOW)  ------>
    *                 <-- present frame (L_FRAME) ---->
    *                 |       <----- new speech (L_FRAME) ---->
    *                 |       |
    *               speech    |
    *                      new_speech
    */      
   new_speech = st->mem_speech + L_TOTAL - L_FRAME - L_FILT + 460;     /* New speech     */
   speech     = st->mem_speech + L_TOTAL - L_FRAME - L_NEXT;     /* Present frame  */
   exc = st->mem_exc + PIT_MAX + L_INTERPOL;
   f_exc = f_old_exc + PIT_MAX + L_INTERPOL;
   wsp = st->mem_wsp + (PIT_MAX / OPL_DECIM);
   for(i = 0; i < L_FRAME16k; i++)
   {
      f_speech16k[i] = (Float32)speech16k[i];
   }
   Q_new = -st->mem_q;
   for(i = 0; i < (PIT_MAX + L_INTERPOL); i++)
   {
      f_old_exc[i] = (Float32)(st->mem_exc[i] * pow(2, Q_new));
   }
   /*
    * Down sampling signal from 16kHz to 12.8kHz
    */
   E_UTIL_decim_12k8(f_speech16k, L_FRAME16k, new_speech, st->mem_decim);
   /* decimate with zero-padding to avoid delay of filter */
   memcpy(f_code, st->mem_decim, 2 * L_FILT16k * sizeof(Float32));
   memset(error, 0, L_FILT16k * sizeof(Float32));
   E_UTIL_decim_12k8(error, L_FILT16k, new_speech + L_FRAME, f_code);
   /*
    * Perform 50Hz HP filtering of input signal.
    * Perform fixed preemphasis through 1 - g z^-1
    */
   E_UTIL_hp50_12k8(new_speech, L_FRAME, st->mem_sig_in);
   memcpy(f_code, st->mem_sig_in,  4 * sizeof(Float32) );
   E_UTIL_hp50_12k8(new_speech + L_FRAME, L_FILT, f_code);
   E_UTIL_f_preemph(new_speech, PREEMPH_FAC, L_FRAME, &(st->mem_preemph));
   /* last L_FILT samples for autocorrelation window */
   f_tmp = st->mem_preemph;
   E_UTIL_f_preemph(new_speech + L_FRAME, PREEMPH_FAC, L_FILT, &f_tmp);
   /*
    *  Call VAD
    *  Preemphesis scale down signal in low frequency and keep dynamic in HF.
    *  Vad work slightly in future (new_speech = speech + L_NEXT - L_FILT).
    */
   vad_flag = E_DTX_vad(st->vadSt, speech + L_NEXT - L_FILT);
   if (vad_flag == 0)
   {
      st->mem_vad_hist = 1;
   }
   else
   {
      st->mem_vad_hist = 0;
   }
   /* DTX processing */
   if (allow_dtx)
   {
      /* Note that mode may change here */
      E_DTX_tx_handler(st->dtx_encSt, vad_flag, mode);
   }
   else
   {
      E_DTX_reset(st->dtx_encSt);
   }
   if(*mode != MRDTX)
   {
      E_MAIN_parm_store(vad_flag, &prms);
   }
   /*
    *  Perform LPC analysis
    *  --------------------
    *   - autocorrelation + lag windowing
    *   - Levinson-durbin algorithm to find a[]
    *   - convert a[] to isp[]
    *   - convert isp[] to isf[] for quantization
    *   - quantize and code the isf[]
    *   - convert isf[] to isp[] for interpolation
    *   - find the interpolated isps and convert to a[] for the 4 subframes
    */
   /* LP analysis centered at 3nd surame */
   E_UTIL_autocorr(st->mem_speech, r);
   E_LPC_lag_wind(r + 1, M);  /* Lagindowing    */
   E_LPC_lev_dur(A, r, M);
   E_LPC_a_isp_conversion(A, ispnew, st->mem_isp, M);  /* From A(z) to isp */
   /* Find the interpolated isps and convert to a[] for all subframes */
   E_LPC_f_int_isp_find(st->mem_isp, ispnew, A, NB_SUBFR, M);
   /* update isp memory for the next frame */
   memcpy(st->mem_isp, ispnew, M * sizeof(Float32));
   /* Convert isps to frequency domain 0..6400 */
   E_LPC_isp_isf_conversion(ispnew, isf, M);
   /* check resonance for pitch clipping algorithm */
   E_GAIN_clip_isf_test(isf, st->mem_gp_clip);
   /*
    *  Perform PITCH_OL analysis
    *  -------------------------
    * - Find the residual res[] for the whole speech frame
    * - Find the weighted input speech wsp[] for the whole speech frame
    * - Find the 2 open-loop pitch estimate
    * - Set the range for searching closed-loop pitch in 1st subframe
    */
   p_A = A;
   for (i_subfr = 0;  i_subfr < L_FRAME; i_subfr += L_SUBFR)
   {
      E_LPC_a_weight(p_A, Ap, GAMMA1, M);
      E_UTIL_residu(Ap, &speech[i_subfr], &wsp[i_subfr], L_SUBFR);
      p_A += (M + 1);
   }
   E_UTIL_deemph(wsp, TILT_FAC, L_FRAME, &(st->mem_wsp_df));
   /* decimation of wsp[] to search pitch in LF and to reduce complexity */
   E_GAIN_lp_decim2(wsp, L_FRAME, st->mem_decim2);
   /* Find open loop pitch lag for whole speech frame */
   if (*mode == MODE_7k)
   {
      /* Find open loop pitch lag for whole speech frame */
      T_op = E_GAIN_open_loop_search(wsp, PIT_MIN / OPL_DECIM,
         PIT_MAX / OPL_DECIM, L_FRAME / OPL_DECIM, st->mem_T0_med,
         &(st->mem_ol_gain), st->mem_hf_wsp, st->mem_hp_wsp,
         st->mem_ol_wght_flg);
   }
   else
   {
      /* Find open loop pitch lag for first 1/2 frame */
      T_op = E_GAIN_open_loop_search(wsp, PIT_MIN / OPL_DECIM,
         PIT_MAX / OPL_DECIM, (L_FRAME / 2) / OPL_DECIM, st->mem_T0_med,
         &(st->mem_ol_gain), st->mem_hf_wsp, st->mem_hp_wsp,
         st->mem_ol_wght_flg);
   }
   if (st->mem_ol_gain > 0.6)
   {
      st->mem_T0_med = E_GAIN_olag_median(T_op, st->mem_ol_lag);
      st->mem_ada_w = 1.0F;
   }
   else
   {
      st->mem_ada_w = st->mem_ada_w * 0.9F;
   }
   if (st->mem_ada_w < 0.8)
   {
      st->mem_ol_wght_flg = 0;
   }
   else
   {
      st->mem_ol_wght_flg = 1;
   }
   E_DTX_pitch_tone_detection(st->vadSt, st->mem_ol_gain);
   T_op *= OPL_DECIM;
   if (*mode != MODE_7k)
   {
      /* Find open loop pitch lag for second 1/2 frame */
      T_op2 = E_GAIN_open_loop_search(wsp + ((L_FRAME / 2) / OPL_DECIM),
         PIT_MIN / OPL_DECIM, PIT_MAX / OPL_DECIM, (L_FRAME / 2) / OPL_DECIM,
         st->mem_T0_med, &st->mem_ol_gain, st->mem_hf_wsp, st->mem_hp_wsp,
         st->mem_ol_wght_flg);
      if (st->mem_ol_gain > 0.6)
      {
          st->mem_T0_med = E_GAIN_olag_median(T_op2, st->mem_ol_lag);
          st->mem_ada_w = 1.0F;
      }
      else
      {
          st->mem_ada_w = st->mem_ada_w * 0.9F;
      }
      if (st->mem_ada_w < 0.8)          
      {
         st->mem_ol_wght_flg = 0;
      }
      else
      {
         st->mem_ol_wght_flg = 1;
      }
      E_DTX_pitch_tone_detection(st->vadSt, st->mem_ol_gain);
      T_op2 *= OPL_DECIM;
   }
   else
   {
      T_op2 = T_op;
   }
   /*
    * DTX-CNG
    */
   if(*mode == MRDTX)
   {
      /* Buffer isf's and energy */
      E_UTIL_residu(&A[3 * (M + 1)], speech, f_exc, L_FRAME);
      f_tmp = 0.0;
      for(i = 0; i < L_FRAME; i++)
      {
         f_tmp += f_exc[i] * f_exc[i];
      }
      E_DTX_buffer(st->dtx_encSt, isf, f_tmp, codec_mode);
      /* Quantize and code the isfs */
      E_DTX_exe(st->dtx_encSt, f_exc2, &prms);
      /* reset speech coder memories */
      E_MAIN_reset(st, 0);
      /*
       * Update signal for next frame.
       * -> save past of speech[] and wsp[].
       */
      memcpy(st->mem_speech, &st->mem_speech[L_FRAME], (L_TOTAL - L_FRAME + 460) * sizeof(Float32));
      memcpy(st->mem_wsp, &st->mem_wsp[L_FRAME / OPL_DECIM],
         (PIT_MAX / OPL_DECIM) * sizeof(Float32));
      return(0);
   }
   /*
    *   ACELP
    */
   /* Quantize and code the isfs */
   if (*mode <= MODE_7k)
   {                                                                        
      E_LPC_isf_2s3s_quantise(isf, isfq, st->mem_isf_q, indice, 4);
      E_MAIN_parm_store((Word16)indice[0], &prms);
      E_MAIN_parm_store((Word16)indice[1], &prms);
      E_MAIN_parm_store((Word16)indice[2], &prms);
      E_MAIN_parm_store((Word16)indice[3], &prms);
      E_MAIN_parm_store((Word16)indice[4], &prms);
   }
   else
   {
      E_LPC_isf_2s5s_quantise(isf, isfq, st->mem_isf_q, indice, 4);
      E_MAIN_parm_store((Word16)indice[0], &prms);
      E_MAIN_parm_store((Word16)indice[1], &prms);
      E_MAIN_parm_store((Word16)indice[2], &prms);
      E_MAIN_parm_store((Word16)indice[3], &prms);
      E_MAIN_parm_store((Word16)indice[4], &prms);
      E_MAIN_parm_store((Word16)indice[5], &prms);
      E_MAIN_parm_store((Word16)indice[6], &prms);
   }
   /* Convert isfs to the cosine domain */
   E_LPC_isf_isp_conversion(isfq, ispnew_q, M);
   if (*mode == MODE_24k)
   {
      /* Check stability on isf : distance between old isf and current isf */
      f_tmp = 0.0F;
      f_pt_tmp = st->mem_isf;
      for (i=0; i < M - 1; i++)
      {
         f_tmp += (isf[i] - f_pt_tmp[i]) * (isf[i] - f_pt_tmp[i]);
      }
      stab_fac = (Float32)(1.25F - (f_tmp / 400000.0F));
      if (stab_fac > 1.0F)
      {
         stab_fac = 1.0F;
      }
      if (stab_fac < 0.0F)
      {
         stab_fac = 0.0F;
      }
      memcpy(f_pt_tmp, isf, M * sizeof(Float32));
   }
   if (st->mem_first_frame == 1)
   {
      st->mem_first_frame = 0;
      memcpy(st->mem_isp_q, ispnew_q, M * sizeof(Word16));
   }
   /* Find the interpolated isps and convert to a[] for all subframes */
   E_LPC_int_isp_find(st->mem_isp_q, ispnew_q, E_ROM_interpol_frac, s_Aq);
   for (i = 0; i < (NB_SUBFR * (M + 1)); i++)
   {
      Aq[i] = s_Aq[i] * 0.000244140625F; /* 1/4096 */
   }
   /* update isp memory for the next frame */
   memcpy(st->mem_isp_q, ispnew_q, M * sizeof(Word16));
   /*
    * Find the best interpolation for quantized ISPs
    */
   p_Aq = Aq;
   for (i_subfr = 0; i_subfr < L_FRAME; i_subfr += L_SUBFR)
   {
      E_UTIL_residu(p_Aq, &speech[i_subfr], &f_exc[i_subfr], L_SUBFR);
      p_Aq += (M + 1);
   }
   /* Buffer isf's and energy for dtx on non-speech frame */
   if(vad_flag == 0)
   {
      f_tmp = 0.0F;
      for(i = 0; i < L_FRAME; i++)
      {
         f_tmp += f_exc[i] * f_exc[i];
      }
      E_DTX_buffer(st->dtx_encSt, isf, f_tmp, codec_mode);
   }
   /* range for closed loop pitch search in 1st subframe */
   T0_min = T_op - 8;
   if (T0_min < PIT_MIN)
   {
      T0_min = PIT_MIN;
   }
   T0_max = T0_min + 15;
   if (T0_max > PIT_MAX)
   {
      T0_max = PIT_MAX;
      T0_min = T0_max - 15;
   }
   /*
    *          Loop for every subframe in the analysis frame
    *          ---------------------------------------------
    *  To find the pitch and innovation parameters. The subframe size is
    *  L_SUBFR and the loop is repeated L_FRAME/L_SUBFR times.
    *     - compute the target signal for pitch search
    *     - compute impulse response of weighted synthesis filter (h1[])
    *     - find the closed-loop pitch parameters
    *     - encode the pitch dealy
    *     - find 2 lt prediction (with / without LP filter for lt pred)
    *     - find 2 pitch gains and choose the best lt prediction.
    *     - find target vector for codebook search
    *     - update the impulse response h1[] for codebook search
    *     - correlation between target vector and impulse response
    *     - codebook search and encoding
    *     - VQ of pitch and codebook gains
    *     - find voicing factor and tilt of code for next subframe.
    *     - update states of weighting filter
    *     - find excitation and synthesis speech
    */
   p_A = A;
   p_Aq = Aq;
   for (i_subfr = 0; i_subfr < L_FRAME; i_subfr += L_SUBFR)
   {
      pit_flag = i_subfr;
      if ((i_subfr == (2 * L_SUBFR)) & (*mode > MODE_7k))
      {
         pit_flag = 0;
         /* range for closed loop pitch search in 3rd subframe */
         T0_min = T_op2 - 8;
         if (T0_min < PIT_MIN)
         {
            T0_min = PIT_MIN;
         }
         T0_max = T0_min + 15;
         if (T0_max > PIT_MAX)  
         {
            T0_max = PIT_MAX;
            T0_min = T0_max - 15;
         }
      }
      /*
       *
       *        Find the target vector for pitch search:
       *        ---------------------------------------
       *
       *             |------|  res[n]
       * speech[n]---| A(z) |--------
       *             |------|       |   |--------| error[n]  |------|
       *                   zero -- (-)--| 1/A(z) |-----------| W(z) |-- target
       *                   exc          |--------|           |------|
       *
       * Instead of subtracting the zero-input response of filters from
       * the weighted input speech, the above configuration is used to
       * compute the target vector.
       *
       */
      for (i = 0; i < M; i++)
      {
         error[i] = (Float32)(speech[i + i_subfr - 16] - st->mem_syn[i]);
      }
      E_UTIL_residu(p_Aq, &speech[i_subfr], &f_exc[i_subfr], L_SUBFR);
      E_UTIL_synthesis(p_Aq, &f_exc[i_subfr], error + M, L_SUBFR, error, 0);
      E_LPC_a_weight(p_A, Ap, GAMMA1, M);
      E_UTIL_residu(Ap, error + M, xn, L_SUBFR);
      E_UTIL_deemph(xn, TILT_FAC, L_SUBFR, &(st->mem_w0));
      /*
       * Find target in residual domain (cn[]) for innovation search.
       */
      /* first half: xn[] --> cn[] */
      memset(f_code, 0, M * sizeof(Float32));
      memcpy(f_code + M, xn, (L_SUBFR / 2) * sizeof(Float32));
      f_tmp = 0.0F;
      E_UTIL_f_preemph(f_code + M, TILT_FAC, L_SUBFR / 2, &f_tmp);
      E_LPC_a_weight(p_A, Ap, GAMMA1, M);
      E_UTIL_synthesis(Ap, f_code + M, f_code + M, L_SUBFR / 2, f_code, 0);
      E_UTIL_residu(p_Aq, f_code + M, cn, L_SUBFR / 2);
      /* second half: res[] --> cn[] (approximated and faster) */
      for(i = (L_SUBFR / 2); i < L_SUBFR; i++)
      {
         cn[i] = f_exc[i_subfr + i];
      }
      /*
       * Compute impulse response, h1[], of weighted synthesis filter
       */
      E_LPC_a_weight(p_A, Ap, GAMMA1, M);
      memset(h1, 0, L_SUBFR * sizeof(Float32));
      memcpy(h1, Ap, (M + 1) * sizeof(Float32));
      E_UTIL_synthesis(p_Aq, h1, h1, L_SUBFR, h1 + (M + 1), 0);
      f_tmp = 0.0;
      E_UTIL_deemph(h1, TILT_FAC, L_SUBFR, &f_tmp);
      /*
       * Closed-loop fractional pitch search
       */
      /* find closed loop fractional pitch  lag */
      if (*mode <= MODE_9k)
      {
         T0 = E_GAIN_closed_loop_search(&f_exc[i_subfr], xn, h1,
            T0_min, T0_max, &T0_frac,
            pit_flag, PIT_MIN, PIT_FR1_8b);
         /* encode pitch lag */
         if (pit_flag == 0)   /* if 1st/3rd subframe */
         {
            /*
             * The pitch range for the 1st/3rd subframe is encoded with
             * 8 bits and is divided as follows:
             *   PIT_MIN to PIT_FR1-1  resolution 1/2 (frac = 0 or 2)
             *   PIT_FR1 to PIT_MAX    resolution 1   (frac = 0)
             */
            if (T0 < PIT_FR1_8b)
            {
               index = (Word16)(T0 * 2 + (T0_frac >> 1) - (PIT_MIN * 2));
            }
            else
            {
               index = (Word16)(T0 - PIT_FR1_8b + ((PIT_FR1_8b - PIT_MIN) * 2));
            }
            E_MAIN_parm_store(index, &prms);
            /* find T0_min and T0_max for subframe 2 and 4 */
            T0_min = T0 - 8;
            if (T0_min < PIT_MIN)   
            {
               T0_min = PIT_MIN;
            }
            T0_max = T0_min + 15;
            if (T0_max > PIT_MAX)
            {
               T0_max = PIT_MAX;
               T0_min = T0_max - 15;
            }
         }
コード例 #3
0
ファイル: enc_if.c プロジェクト: BOTCrusher/sagetv
/*
 * E_IF_encode
 *
 *
 * Parameters:
 *    st                I: pointer to state structure
 *    mode              I: Speech Mode
 *    speech            I: Input speech
 *    serial            O: Output octet structure IF2 or 16-bit serial stream
 *    dtx               I: use DTX
 *
 * Function:
 *    Encoding and packing one frame of speech
 *
 * Returns:
 *    number of octets
 */
int E_IF_encode(void *st, Word16 req_mode, Word16 *speech, UWord8 *serial,
                Word16 dtx)
{
   Word16 prms[NB_PARM_MAX];
   Word32 i;
   Word16 frame_type, mode, reset_flag;
   WB_enc_if_state *s;

   s = (WB_enc_if_state *)st;
   mode = req_mode;

   /* check for homing frame */
   reset_flag = E_IF_homing_frame_test(speech);

   if (!reset_flag)
   {
      for (i = 0; i < L_FRAME16k; i++)   /* Delete the 2 LSBs (14-bit input) */
      {
         speech[i] = (Word16) (speech[i] & 0xfffC);
      }

      E_MAIN_encode(&mode, speech, prms, s->encoder_state, dtx);

      if (mode == MRDTX)
      {
         s->sid_update_counter--;

         if (s->prev_ft == TX_SPEECH)
         {
            frame_type = TX_SID_FIRST;
            s->sid_update_counter = 3;
         }
         else
         {
            if ((s->sid_handover_debt > 0) && (s->sid_update_counter > 2))
            {
               /*
                * ensure extra updates are
                * properly delayed after a possible SID_FIRST
                */
               frame_type = TX_SID_UPDATE;
               s->sid_handover_debt--;
            }
            else
            {
               if (s->sid_update_counter == 0)
               {
                  frame_type = TX_SID_UPDATE;
                  s->sid_update_counter = 8;
               }
               else
               {
                  frame_type = TX_NO_DATA;
                  mode = MRNO_DATA;
               }
            }
         }
      }
      else
      {
         s->sid_update_counter = 8;
         frame_type = TX_SPEECH;
      }

      s->prev_ft = frame_type;

   }
   /* perform homing if homing frame was detected at encoder input */
   else
   {
      E_MAIN_reset(s->encoder_state, 1);
      E_IF_sid_sync_reset(s);
      E_IF_homing_coding(prms, mode);
      frame_type = TX_SPEECH;
   }

#ifdef IF2
   return E_IF_if2_conversion(mode, prms, serial, frame_type, req_mode);
#else
   return E_IF_mms_conversion(mode, prms, serial, frame_type, req_mode);
#endif
}