rfc741.txt

RFC 相关的技术文档

   Following  is the definition  for the  format  of  the  SIMPLE-SIMPLE
   coding, according to Tables-Set-#1:

   For each parcel:

      PITCH              6 bits  (PITCH=0 for UNVOICED)

      GAIN               5 bits

      I(1)               7 bits

      I(2)               7 bits

      I(3)               6 bits

      I(4)               6 bits

      I(5)               5 bits

      I(6)               5 bits

      I(7)               5 bits

      I(8)               5 bits

      I(9)               5 bits

      I(10)              5 bits

   where  each of the I(j)  is an index  for  inverse  sine  coding.  If
   K(j)=arcsin(Theta(j))  and N bits are assigned  for its transmission,
   then I(j)=(Theta(j)/Pi)*2**N.

   Hence  at  each  transmission   interval   (128  samples   times  150
   microseconds)  67 bits are sent, which results in a data rate of 3490
   bps.  Since this bandwidth  is well within  the capabilities  of  the
   network,  SIMPLE-SIMPLE  coding  is used,  which requires  the  least
   computation  by the hosts.  Note that this data rate is a peak  rate,
   without the use of silence.













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NWG/RFC 741                                           DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)



                 4.  EXAMPLES FOR THE CONTROL PROTOCOL

   Here is an example for a connection:

      (377)  C: 1,<WHO>,<WHOM>,340    Please talk to me on 340/341.

      (340)  A: 2,1                   I refuse, since I'm busy.

   Another example:

      (377)  C: 1,<WHO>,<WHOM>,360    Please talk to me on 360/361.

      (360)  A: 6,350                 OK.  You talk to me on 350/351.

      (350)  C: 1,<WHO>,<WHOM>        I want to talk to you.

      (360)  A: 3,1,1,2               Can you do CVSD?  (ANSWERER tries
                                      to be the NEGOTIATION MASTER)

      (350)  C: 12,1                  I want to be it.

      (360)  A: 13,1                  That's OK with me.

      (350)  C: 3,1,1,2               Can you do CVSD?

      (360)  A: 5,1,1                 No, but I can do LPC.

      (350)  C: 3,1,1,3               Can you do RELP?

      (360)  A: 5,1,1                 No, but I can do LPC.

      (350)  C: 3,1,1,1               How about LPC?

      (360)  A: 4,1,1                 LPC is fine with me.

      (350)  C: 3,2,1,150             Can you use 150 microseconds
                                      sampling?

      (360)  A: 4,2,150               I can use 150 microseconds.

      (350)  C: 3,4,3,976,1040,2016   Can you use 976, 1040, or 2016
                                      bits/msg?

      (360)  A: 4,4,976               I can use 976.

      (350)  C: 3,5,1,10              Can you send 10 coefficients?

      (360)  A: 4,5,10                I can send 10.




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NWG/RFC 741                                           DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)



      (350)  C: 3,6,1,64              Can you use a 64 sample
                                      transmission?

      (360)  A: 4,6,64                I can use 64.

      (350)  C: 3,7,2,1,2             SIMPLE or OPTIMIZED acoustic
                                      coding?

      (360)  A: 4,7,2                 OPTIMIZED!

      (350)  C: 3,8,1,1               Can you do SIMPLE info coding?

      (360)  A: 4,8,1                 I can do SIMPLE.

      (350)  C: 3,9,1,58              mu = 0.90625?

      (360)  A: 4,9,58                Fine with me.

      (350)  C: 3,10,1                Table set #1?

      (360)  A: 4,10,1                Of course!

      (350)  C: 6                     I am ready.  (Note:  No "RINGING"
                                      sent)

      (350)  C: 8                     And you?

      (360)  A: 6                     I am ready, too.

         .......                      Data is exchanged now,

         .......                      on 351 and 361.

      (350)  C: 10,1234               Echo it, please.

      (360)  A: 11,1234               Here it comes!

         .......

      (360)  A: 10,3333               Now ANSWERER wants to measure

      (350)  C: 11,3333               ...the delays, too.

         .......

      (???)    X: 2,3                 Termination by either user.






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NWG/RFC 741                                           DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)



   Another example:

      (377)  C: 1,<WHO>,<WHOM>,360    Please talk to me on 360/361.

      (360)  A: 6,340                 Fine.  You send on 340/341.

      (340)  C: 1,<WHO>,<WHOM>        I want to talk to you.

      (360)  A: 3,3,1,1               Can you use V1?

      (340)  C: 4,3,1                 Yes, V1 is OK.

      (360)  A: 3,4,1,1984            Can you use up to 1984 bits/msg?

      (340)  C: 5,4,976               No, but I can use 976.

      (360)  A: 3,4,1,976             Can you use up to 976 bits/msg?

      (340)  C: 4,4,976               I can use 976.

      (360)  A: 9                     Ringing (note how short this
                                      negotiation is!!).

         .......

      (340)  C: 8                     Still there?

      (360)  A: 9                     Still ringing.

         .......

      (340)  C: 8                     Still there?

      (360)  A: 9                     Still ringing.

         .......

      (340)  C: 8                     How about it?

      (360)  A: 9                     Still ringing.

      (340)  C: 2                     Forget it!  (No reason given.)










Cohen                                                          [Page 17]

NWG/RFC 741                                           DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)



                               APPENDIX 1

   

                           THE DEFINITION OF:

                             TABLES-SET-#1
      
      
      
      
      

                                   by

                             John D. Markel

                Speech Communication Research Laboratory

                       Santa Barbara, California
































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NWG/RFC 741                                           DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)



                             TABLES-SET-#1

   This set includes tables for:
   
   
   
   

      PITCH -  64 values, PITCH table
      GAIN  -  32 values, GAIN table
      I( 1) - 128 values, INDEX7 table
      I( 2) - 128 values, INDEX7 table
      I( 3) -  64 values, INDEX6 table
      I( 4) -  64 values, INDEX6 table
      I( 5) -  32 values, INDEX5 table
      I( 6) -  32 values, INDEX5 table
      I( 7) -  32 values, INDEX5 table
      I( 8) -  32 values, INDEX5 table
      I( 9) -  32 values, INDEX5 table
      I(10) -  32 values, INDEX5 table

   These tables  are defined  specifically  for a sampling period of 150
   microseconds.





























Cohen                                                          [Page 19]

NWG/RFC 741                                           DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)



   GENERAL COMMENTS

      The following  tables  are arranged in three columns, {X(j)}, {j},
      and {R(j)}.  Note that the entries in the {X(j)} column are half a
      step off the other columns.  This is to  indicate  that  INTERVALS
      from X-domain (pitch, gain, and the Ks) are mapped into CODES {j},
      which are transmitted  over the network,  to be translated  by the
      receiver   into  the  {R(j)}.   These  intervals  are  defined  as
      OPEN-CLOSE  intervals.  For  example,  the  PITCH  value  (at  the
      transmitter)  of 4131 belongs to the interval "(4024,4131]", hence
      it is coded  as j=6 which  is mapped  by the receiver to the value
      21.  Similarly, the value of 2400 for INDEX7 is found to belong to
      the interval  "(2009,2811]", coded into the CODE 3 and mapped back
      into 2411.

      Note  that  if N bits  are used  by a certain CODE, then there are
      2**N+1  entries  in the X-table,  but only  2**N  entries  in  the
      R-table.

      The  transformation   values   used  for  PITCH,   GAIN,  and  the
      K-parameters  (in the X- and R-tables)  are as defined in NSC Note
      42.

      Values  above  and below  the range of the X-table are mapped into
      the maximum and minimum table indices, respectively.

      Note that R(J) of INDEX5 is identical to R(2J) of INDEX6, and that
      R(J)  of INDEX6  is identical to R(2J) of INDEX7. Therefore, it is
      possible to store only the R-table of INDEX7, without the R-tables
      of INDEX5 and INDEX6.

      In the SPS-41 implementation there is no need to store any R-table
      for the K-parameters.  The transmitted  index can be used directly
      (with the appropriate  scaling)  as an index into the SPS built-in
      TRIG tables.

   COMMENTS ON THE PITCH TABLE

      The level J=0 defines the UNVOICED condition. The receiver maps it
      into the number of samples per frame (here 128).

      This PITCH table differs  significantly  from previous  tables and
      supersedes  the table published  in NSC Note 36.  Details  of  the
      calculation  of the table  can be found  in NSC Note 42. Immediate
      questions should be referred to John Markel.







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Specifications for the Network Voice Protocol (NVP)



   COMMENTS ON THE GAIN TABLE

      The level J=0 defines absolute silence.

      This table  is designed  for a maximum  of 12-bit  A/D input,  and
      allows for a dynamic range of 43.5 dB.

      NSC Notes  36, 45, 56 and 58 supply background for the GAIN table.
      Gain is the energy of the pre-emphasized, windowed signal.

      This table  is the NEW GAIN table. NSC Notes 56 and 58 explain the
      reasoning behind the NEW GAIN.

   COMMENTS ON THE INDEX7 TABLE

      Positive values are coded into the range [0-63, decimal]. Negative
      values  are coded into the 7-bits two's complement of the codes of
      their absolute value [65-127, decimal].

      Note that all values -403 < V < 403 are coded as (and mapped into)
      0. Note also that the code -64 (100 octal) is never used.

      In  SPS-41  implementation,  the  R-table  is  not  needed,  since
      TRIG(2J) is the needed value R(J).

   COMMENTS ON THE INDEX6 TABLE

      Positive values are coded into the range [0-31, decimal]. Negative
      values  are coded into the 6-bits two's complement of the codes of
      their absolute values [33-63, decimal].

      Note that all values -805 < V < 805 are coded as (and mapped into)
      0. Note also that the code -32 (40 octal) is never used.

      In  SPS-41  implementation,  the  R-table  is  not  needed,  since
      TRIG(4J) is the needed value R(J).

   COMMENTS ON THE INDEX5 TABLE

      Positive  numbers  are  coded  into  the  range  [0-15,  decimal].
      Negative  numbers  are coded into the 5-bits  two's complement  of
      their absolute values, i.e., [17-31, decimal].

      Note  that  all values  -1609  < V < 1609 are coded as (and mapped
      into) 0. Note also that the code -16 (20 octal) is never used.

      In  SPS-41  implementation,  the  R-table  is  not  needed,  since
      TRIG(8J) is the needed value R(J).




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NWG/RFC 741                                           DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)



   THE PITCH TABLE (as of 10-29-74)

      X(J)    J  R(J)           X(J)    J  R(J)          X(J)    J  R(J)

         0                      6002                     10770
              0  128*                  21   33                   42   61
         0                      6168                     11080
              1   18                   22   34                   43   63
      3630                      6338                     11399
              2   19                   23   35                   44   65
      3724                      6515                     11728
              3   19                   24   36                   45   67
      3821                      6696                     12067
              4   20                   25   37                   46   69
      3921                      6883                     12417
              5   20                   26   38                   47   71
      4024                      7075                     12776
              6   21                   27   39                   48   73
      4131                      7274                     13147
              7   22                   28   40                   49   75
      4240                      7478                      13529
              8   22                   29   41                   50   77
      4353                      7689                     13922
              9   23                   30   43                   51   80
      4469                      7905                     14327
             10   24                   31   44                   52   82
      4588                      8129                     14745