www.pudn.com > g729Decoder.rar > ENC_LAG3.asm

;========================================================================== 
;  File Name 
;  ---------- 
;  ENC_LAG3.ASM 
; 
;  Brief Description of the Code: 
;  ------------------------------ 
;  Encoding of fractional pitch lag with 1/3 resolution. 
; 
;  Ref 
;  ------ 
;  PITCH.C (enc_lag3) 
;========================================================================== 
 
 
        .mmregs 
 
        .include  ..\include\const.h 
        .include  ..\include\tab_ld8a.h 
        .include  ..\include\ld8amem.h 
 
        .def      Enc_lag3 
 
 
;---------------------------------------------------------------------- 
;  Enc_lag3 
;---------------------------------------------------------------------- 
; The pitch range for the first subframe is divided as follows: 
;   19 1/3  to   84 2/3   resolution 1/3 
;   85      to   143      resolution 1 
; 
; The period in the first subframe is encoded with 8 bits. 
; For the range with fractions: 
;   index = (T-19)*3 + frac - 1;   where T=[19..85] and frac=[-1,0,1] 
; and for the integer only range 
;   index = (T - 85) + 197;        where T=[86..143] 
;---------------------------------------------------------------------- 
; For the second subframe a resolution of 1/3 is always used, and the 
; search range is relative to the lag in the first subframe. 
; If t0 is the lag in the first subframe then 
;  t_min=t0-5   and  t_max=t0+4   and  the range is given by 
;       t_min - 2/3   to  t_max + 2/3 
; 
; The period in the 2nd subframe is encoded with 5 bits: 
;   index = (T-(t_min-1))*3 + frac - 1;    where T[t_min-1 .. t_max+1] 
;---------------------------------------------------------------------- 
;  Word16 Enc_lag3(     /* output: Return index of encoding */ 
;    Word16 T0,         /* input : Pitch delay              */ 
;    Word16 T0_frac,    /* input : Fractional pitch delay   */ 
;    Word16 *T0_min,    /* in/out: Minimum search delay     */ 
;    Word16 *T0_max,    /* in/out: Maximum search delay     */ 
;    Word16 pit_min,    /* input : Minimum pitch delay      */ 
;    Word16 pit_max,    /* input : Maximum pitch delay      */ 
;    Word16 pit_flag    /* input : Flag for 1st subframe    */ 
;  ) 
;---------------------------------------------------------------------- 
;  Constants :  Addr_T0 -> T0 
;               Addr_T0_frac -> T0_frac 
;               Addr_T0_min  -> T0_min 
;               Addr_T0_max  -> T0_max 
; 
;               PIT_MIN = pit_min 
;               PIT_MAX = pit_max 
; 
;  Input : A = pit_flag 
; 
;  Output : B = Enc_lag3(xxxxxx) 
;---------------------------------------------------------------------- 
;  The following variables must be in same data page : 
;               Addr_T0 -> T0 
;               Addr_T0_frac -> T0_frac 
;               Addr_T0_min  -> T0_min 
;               Addr_T0_max  -> T0_max 
;---------------------------------------------------------------------- 
 
 
        .asg    "Addr_T0", T0 
        .asg    "Addr_T0_frac", T0_frac 
        .asg    "Addr_T0_min",  T0_min 
        .asg    "Addr_T0_max",  T0_max 
 
Enc_lag3: 
        LD      #T0, DP 
        LD      T0, B 
        BC      SecondSufr, ANEQ 
FirstSufr: 
                SUB     #85, B, A 
                BC      T0_GT_85, AGT 
                        LD      B,1,A 
                        ADD     A,  B  
                        SUB     #58,B 
                        ADD     T0_frac, B 
                        STLM    B,T 
                        B       T0_LT_85 
T0_GT_85: 
                ADD     #112, B, A 
                STLM    A, T 
 
T0_LT_85: 
        LD      #-5, A 
        ADD     T0, A 
        LD      #PIT_MIN, B 
        MAX     A 
        LD      #PIT_MAX - 9, B 
        MIN     A 
        ADD     #9, A, B 
        STL     A, T0_min 
        STL     B, T0_max 
        RETD 
        LDM     T, B 
 
SecondSufr: 
        SUB     T0_min, B 
        LD      B,1,A 
        ADD     A,B 
        ADD     T0_frac, B 
        RETD 
        ADD     #2, B