head	1.3;access;symbols;locks; strict;comment	@* @;1.3date	96.03.21.15.14.57;	author jaf;	state Exp;branches;next	1.2;1.2date	96.03.13.18.55.10;	author jaf;	state Exp;branches;next	1.1;1.1date	96.02.07.14.43.31;	author jaf;	state Exp;branches;next	;desc@@1.3log@Added comments about which indices of argument arrays are read orwritten, and about the one bit of local state in CHANWR.  CHANRDhas no local state.@text@**************************************************************************	CHANL Version 49** $Log: chanwr.f,v $* Revision 1.2  1996/03/13  18:55:10  jaf* Comments added explaining which of the local variables of this* subroutine need to be saved from one invocation to the next, and which* do not.** Revision 1.1  1996/02/07 14:43:31  jaf* Initial revision**************************************************************************** CHANWR:*   Place quantized parameters into bitstream** Input:*  ORDER  - Number of reflection coefficients (not really variable)*  IPITV  - Quantized pitch/voicing parameter*  IRMS   - Quantized energy parameter*  IRC    - Quantized reflection coefficients*           Indices 1 through ORDER read.* Output:*  IBITS  - Serial bitstream*           Indices 1 through 54 written.*           Bit 54, the SYNC bit, alternates from one call to the next.* * Subroutine CHANWR maintains one bit of local state from one call to* the next, in the variable ISYNC.  I believe that this one bit is only* intended to allow a receiver to resynchronize its interpretation of* the bit stream, by looking for which of the 54 bits alternates every* frame time.  This is just a simple framing mechanism that is not* useful when other, higher overhead framing mechanisms are used to* transmit the coded frames.* * I'm not going to make an entry to reinitialize this bit, since it* doesn't help a receiver much to know whether the first sync bit is a 0* or a 1.  It needs to examine several frames in sequence to have* reasonably good assurance that its framing is correct.*** CHANRD:*   Reconstruct parameters from bitstream** Input:*  ORDER  - Number of reflection coefficients (not really variable)*  IBITS  - Serial bitstream*           Indices 1 through 53 read (SYNC bit is ignored).* Output:*  IPITV  - Quantized pitch/voicing parameter*  IRMS   - Quantized energy parameter*  IRC    - Quantized reflection coefficients*           Indices 1 through ORDER written** Entry CHANRD has no local state.****   IBITS is 54 bits of LPC data ordered as follows:*	R1-0, R2-0, R3-0,  P-0,  A-0,*	R1-1, R2-1, R3-1,  P-1,  A-1,*	R1-2, R4-0, R3-2,  A-2,  P-2, R4-1,*	R1-3, R2-2, R3-3, R4-2,  A-3,*	R1-4, R2-3, R3-4, R4-3,  A-4,*	 P-3, R2-4, R7-0, R8-0,  P-4, R4-4,*	R5-0, R6-0, R7-1,R10-0, R8-1,*	R5-1, R6-1, R7-2, R9-0,  P-5,*	R5-2, R6-2,R10-1, R8-2,  P-6, R9-1,*	R5-3, R6-3, R7-3, R9-2, R8-3, SYNC	SUBROUTINE CHANWR( ORDER, IPITV, IRMS, IRC, IBITS )*       Arguments	INTEGER ORDER, IPITV, IRMS, IRC(ORDER), IBITS(54)*       Parameters/constants*       These arrays are not Fortran PARAMETER's, but they are defined*       by DATA statements below, and their contents are never altered.	INTEGER IBLIST(53), BIT(10)*       Local variables that need not be saved	INTEGER I	INTEGER ITAB(13)*       Local state*       ISYNC is only used by CHANWR, not by ENTRY CHANRD.	INTEGER ISYNC	SAVE ISYNC	DATA ISYNC/0/	DATA BIT/ 2, 4, 8, 8, 8, 8, 16, 16, 16, 16 /	DATA IBLIST/13, 12, 11, 1, 2, 13, 12, 11, 1, 2, 13, 10,     1             11, 2, 1, 10, 13, 12, 11, 10, 2, 13, 12, 11,     1             10, 2, 1, 12, 7, 6, 1, 10, 9, 8, 7, 4,     1              6, 9, 8, 7, 5, 1, 9, 8, 4, 6, 1, 5,     1              9, 8, 7, 5, 6 /*************************************************************************	Place quantized parameters into bitstream*************************************************************************   Place parameters into ITAB	ITAB(1) = IPITV	ITAB(2) = IRMS	ITAB(3) = 0	DO I = 1,ORDER	   ITAB(I+3) = AND( IRC(ORDER+1-I), 32767 )	END DO*   Put 54 bits into IBITS array	DO I = 1,53	   IBITS(I) = AND(ITAB(IBLIST(I)),1)	   ITAB(IBLIST(I)) = ITAB(IBLIST(I)) / 2	END DO	IBITS(54) = AND(ISYNC,1)	ISYNC = 1 - ISYNC	RETURN*************************************************************************	Reconstruct parameters from bitstream************************************************************************	ENTRY CHANRD( ORDER, IPITV, IRMS, IRC, IBITS )*   Reconstruct ITAB	DO I = 1,13	   ITAB(I) = 0	END DO	DO I = 1,53	   ITAB(IBLIST(54-I)) = ITAB(IBLIST(54-I))*2 + IBITS(54-I)	END DO*   Sign extend RC's	DO I = 1,ORDER	   IF( AND( ITAB(I+3), BIT(I) ) .NE. 0 )     1    ITAB(I+3) = ITAB(I+3) - 2*BIT(I)	END DO*   Restore variables	IPITV = ITAB(1)	IRMS = ITAB(2)	DO I = 1,ORDER	   IRC(I) = ITAB(ORDER+4-I)	END DO	RETURN	END@1.2log@Comments added explaining which of the local variables of thissubroutine need to be saved from one invocation to the next, and whichdo not.@text@d6 5d20 24a43 7*   Inputs:*    ORDER  - Number of reflection coefficients (not really variable)*    IPITV  - Quantized pitch/voicing parameter*    IRMS   - Quantized energy parameter*    IRC    - Quantized reflection coefficients*   Output:*    IBITS  - Serial bitstreamd48 13a60 7*   Inputs:*    ORDER  - Number of reflection coefficients (not really variable)*    IBITS  - Serial bitstream*   Outputs:*    IPITV  - Quantized pitch/voicing parameter*    IRMS   - Quantized energy parameter*    IRC    - Quantized reflection coefficientsd76 1a76 1*       Parametersd80 11a90 6*       Local variables*       *       None of these, except ISYNC, need to have their values saved*       from one invocation to the next.*       *       In fact, IBLIST and BIT are constant arrays.d92 9a101 2	INTEGER I, ISYNC	INTEGER ITAB(13), IBLIST(53), BIT(10)a107 2	DATA ISYNC/0/	SAVE ISYNC@1.1log@Initial revision@text@d5 4a8 1* $Log$d47 3d51 9d69 1@