💾 Archived View for gemini.bortzmeyer.org › rfc-mirror › rfc741.txt captured on 2023-09-28 at 23:04:33.
⬅️ Previous capture (2021-11-30)
-=-=-=-=-=-=-
NWG/RFC 741 DC 22 Nov 77 42444
SPECIFICATIONS FOR THE
NETWORK VOICE PROTOCOL (NVP)
and
Appendix 1: The Definition of Tables-Set-#1 (for LPC)
Appendix 2: Implementation Recommendations
NSC NOTE 68
(Revision of NSC Notes 26, 40, and 43)
Danny Cohen, ISI
January 29, 1976
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
CONTENTS
PREFACE iii
ACKNOWLEDGMENTS iv
INTRODUCTION 2
THE CONTROL PROTOCOL 2
Summary of the CONTROL Messages 3
Definition of the CONTROL Messages 4
Definition of the <WHAT> and <HOW>
Negotiation Tables 8
On RENEGOTIATION 10
The Header of Data Messages 10
THE LPC DATA PROTOCOL 13
EXAMPLES FOR THE CONTROL PROTOCOL 15
APPENDIX 1: THE DEFINITION OF TABLES-SET-#1 18
General Comments 20
Comments on the PITCH Table 20
Comments on the GAIN Table 21
Comments on the INDEX7 Table 21
Comments on the INDEX6 Table 21
Comments on the INDEX5 Table 21
The PITCH Table 22
The GAIN Table 24
The INDEX7 Table 25
The INDEX6 Table 26
The INDEX5 Table 27
APPENDIX 2: IMPLEMENTATION RECOMMENDATIONS 28
REFERENCES 30
Cohen [Page ii]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
PREFACE
The major objective of ARPA's Network Secure Communications (NSC)
project is to develop and demonstrate the feasibility of secure,
high-quality, low-bandwidth, real-time, full-duplex (two-way) digital
voice communications over packet-switched computer communications
networks. This kind of communication is a very high priority
military goal for all levels of command and control activities.
ARPA's NSC projrct will supply digitized speech which can be secured
by existing encryption devices. The major goal of this research is
to demonstrate a digital high-quality, low-bandwidth, secure voice
handling capability as part of the general military requirement for
worldwide secure voice communication. The development at ISI of the
Network Voice Protocol described herein is an important part of the
total effort.
Cohen [Page iii]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
ACKNOWLEDGMENTS
The Network Voice Protocol (NVP), implemented first in December 1973,
and has been in use since then for local and transnet real-time voice
communication over the ARPANET at the following sites:
o Information Sciences Institute, for LPC and CVSD, with a
PDP-11/45 and an SPS-41.
o Lincoln Laboratory, for LPC and CVSD, with a TX2 and the
Lincoln FDP, and with a PDP-11/45 and the LDVT.
o Culler-Harrison, Inc., for LPC, with the Culler-Harrison
MP32A and AP-90.
o Stanford Research Institute, for LPC, with a PDP-11/40 and an
SPS-41.
The NVP's success in bridging the differences between the above
systems is due mainly to the cooperation of many people in the
ARPA-NSC community, including Jim Forgie (Lincoln Laboratory), Mike
McCammon (Culler-Harrison), Steve Casner (ISI) and Paul Raveling
(ISI), who participated heavily in the definition of the control
protocol; and John Markel (Speech Communications Research
Laboratory), John Makhoul (Bolt Beranek & Newman, Inc.) and Randy
Cole (ISI), who participated in the definition of the data protocol.
Many other people have contributed to the NVP-based effort, in both
software and hardware support.
Cohen [Page iv]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
1. INTRODUCTION
Currently, computer communication networks are designed for data
transfer. Since there is a growing need for communication of
real-time interactive voice over computer networks, new communication
discipline must be developed. The current HOST-to-HOST protocol of
the ARPANET, which was designed (and optimized) for data transfer,
was found unsuitable for real-time network voice communication.
Therefore this Network Voice Protocol (NVP) was designed and
implemented.
Important design objectives of the NVP are:
- Recovery of loss of any message without catastrophic effects.
Therefore all answers have to be unambiguous, in the sense that
it must be clear to which inquiry a reply refers.
- Design such that no system can tie up the resources of another
system unnecessarily.
- Avoidance of end-to-end retransmission.
- Separation of control signals from data traffic.
- Separation of vocoding-dependent parts from vocoding-independent
parts.
- Adaptation to the dynamic network performance.
- Optimal performance, i.e. guaranteed required bandwidth, and
minimized maximum delay.
- Independence from lower level protocols.
The protocol consists of two parts:
(1) The control protocol,
(2) The data protocol.
Control messages are sent as controlled (TYPE 0/0) messages, and data
messages may be sent as either controlled (TYPE 0/0) or uncontrolled
(TYPE 0/3) messages (see BBN Report 1822 for definition of
MESSAGE-TYPE).
Throughout this document a "word" means a "16-bit quantity".
Cohen [Page 1]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
2. THE CONTROL PROTOCOL
Throughout this document the 12-bit MESSAGE-ID (see BBN Report 1822)
is referred to as LINK (its 8 MSBs) and SUB-LINK (its 4 LSBs).
The control protocol starts with an initial connection phase on link
377 and continues on other links assigned at run time.
Four links are used for each voice communication:
Link L will be used for control, from CALLER to ANSWERER.
Link K will be used for control, from ANSWERER to CALLER.
Link L+1 will be used for data, from CALLER to ANSWERER.
Link K+1 will be used for data, from ANSWERER to CALLER.
Both L and K should be between 340 and 375 (octal). L and K need not
differ.
The first message (CALLER to ANSWERER) on link 377 indicates which
user wants to talk to whom and specifies K. As a response (on K), the
ANSWERER either refuses the call or accepts it and assigns L.
The CALLER then calls again (this time on link L). The ANSWERER
initiates a negotiation session to verify the compatibility of the
two parties.
The negotiation consists of suggestions put forth by one of the
parties, which are either accepted or rejected by the other party.
The suggesting party in the negotiation is called the NEGOTIATION
MASTER. The other party is called the NEGOTIATION SLAVE. Usually the
ANSWERER is the negotiation master, unless agreed otherwise by the
method described later.
If the negotiation fails, either party may terminate the call by
sending a "GOODBYE". If the negotiation is successfully ended, the
ANSWERER rings bells to draw human attention and sends "RINGING" to
the CALLER. When the call is answered (by a human), a "READY" is sent
to the CALLER and the data starts flowing (on L+1 and K+1). However,
a "READY" can be sent without a preceeding "RINGING".
This bell ringing occurs only after the initial call (not after
renegotiation).
The assignment of L and K cannot be changed after the initial
connection phase.
Only one control message can be sent in a network-message. Extra bits
needed to fill the network-message are ignored.
Cohen [Page 2]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
The length of control messages should never exceed a single-packet
(i.e., 1,007 data bits).
Control messages not recognized by their receiver should be ignored
and should not cause any error condition resuting in termination of
the connection. These messages may result from differences in
implementation level between systems.
SUMMARY OF THE CONTROL MESSAGES
#1 "1,<WHO>,<WHOM>,K"
#2 "2,<CODE>" or only "2"
#3 "3,<WHAT>,<N>,<HOW(1),...HOW(N)>"
#4 "4,<WHAT>,<HOW>"
#5 "5,<WHAT>,<HOW>" or only "5,<WHAT>"
#6 "6,L" or only "6"
#7 "7"
#8 "8"
#9 "9"
#10 "10,<ID>"
#11 "11,<ID>"
#12 "12,<IM>"
#13 "13,<YM>,<OK>"
Cohen [Page 3]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
DEFINITION OF THE CONTROL MESSAGES
#1 CALLING (on 377 and L)
This call is issued first on link 377 and later on link L. Its
format is "1,<WHO>,<WHOM>,K", where <WHO> and <WHOM> are words
which identify respectively the calling party and the party
that is being called, and K is as defined above. The format of
the <WHO> and <WHOM> is:
(HHIIIIIIXXXXXXXX)
where HH are 2 bits identifying the HOST, followed by 6 bits
identifying the IMP, followed by 8 bits identifying the
extension (needed because there may be more than one
communication unit on the same HOST).
The system which sends this message is defined as the CALLER,
and the other system is defined as the ANSWERER.
#2 GOODBYE (TERMINATION, on L or K)
This message has the purpose of terminating calls at any stage.
ICP can be terminated (on K) either negatively by sending
either a single word "2" ("GOODBYE") or the two words
"2,<CODE>", or positively by sending the two words "6,L", as
described later.
After the initial connection phase, calls can be terminated by
either the CALLER (on L) or the ANSWERER (on K). This
termination has two words: "2,<CODE>", where <CODE> is the
reason for the termination, as specified here:
0. Other than the following.
1. I am busy.
2. I am not authorized to talk with you.
3. Request of my user.
4. We believe you are down.
5. Systems incompatibility (NEGOTIATION failure).
6. We have problems.
7. I am in a conference now.
Cohen [Page 4]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
8. You made a protocol error.
#3 NEGOTIATION INQUIRY (on L or K)
Sent by the NEGOTIATION MASTER for compatibility verification.
The format is:
"3,<WHAT>,<LIST-LENGTH>,<HOW-LIST>", meaning
"CAN-YOU-DO,<WHAT>,<LIST-LENGTH>,<HOW-LIST>".
The <HOW-LIST> is a list of pointers into agreed-upon tables,
as shown below.
#4 POSITIVE NEGOTIATION RESPONSE (on L or K)
Sent by the NEGOTIATION SLAVE in response to a NEGOTIATION
INQUIRY. The format is:
"4,<WHAT>,<HOW>", meaning: "I-CAN-DO,<WHAT>,<HOW>".
#5 NEGATIVE NEGOTIATION RESPONSE (on L or K)
Sent by the NEGOTIATION SLAVE in response to a NEGOTIATION
INQUIRY. The format is either:
"5,<WHAT>,0", meaning "I-CAN'T-DO-<WHAT>-IN-ANY-OF-THESE-WAYS",
or: "5,<WHAT>,N", meaning inability to accept any of the
options offered in the INQUIRY, but using "N" as a suggestion
to the ANSWERER about another possibility. Examples are
presented later in this report.
#6 READY (on L or K)
Sent by either party to indicate readiness to accept data. Its
format is "6,L" in the reply to the initial call, and "6"
thereafter.
#7 NOT READY (on L or K)
Sent by either party to indicate unreadiness to accept data. It
is always a single word: "7".
#8 INQUIRY (on L or K)
Sent by either party to inquire about the status of the other.
It is always a single word: "8". It is answered by #6, #7, or
#9.
Cohen [Page 5]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
#9 RINGING (on K)
Sent by the ANSWERER after the negotiations have been
successfully terminated and human permission is needed to
proceed further. The ringing will continue for 10 seconds, and
then stop, UNLESS a #8 is received. This message is always a
single word: "9".
#10 ECHO REQUEST (on L or K)
Sent by whichever party is interested in measuring the network
delays. Its only purpose is to be echoed immediately. The
format is "10,<ID>", where <ID> is any word used to identify
the ECHO.
#11 ECHO (on L or K)
Sent in response to ECHO REQUEST. The format is "11,<ID>",
where <ID> is the word specified by #10. The implementation of
this feature is not compulsory, and no connection should be
terminated due to lack of response to ECHO-REQUEST.
#12 RENEGOTIATION REQUEST (on L or K)
Can be sent by either party at ANY stage after LINKS are agreed
upon. This message consists of the two words "12,<IM>". If the
word <IM> (for I MASTER) is non-zero, the sender of this
message requests to be the NEGOTIATION MASTER. If it is zero,
the receiver of this message is requested to be the NEGOTIATION
MASTER. Renegotiation is described later.
#13 RENEGOTIATION APPROVAL (on L or K)
This message may be sent by either party in response to
RENEGOTIATION REQUEST. It consists of the three words
"13,<YM>,<OK>". If <OK> is non-zero, this is a positive
acknowledgment (approval). If it is zero, this is a negative
acknowledgment (i.e., refusal). <YM> is set to be equal to the
<IM> of #12, for identification purposes.
Messages #7, #8, and #9 are always a single word. Messages #1, #3,
#4, and #5 are several words long. Messages #2 and #6 are either a
single word or two words long. #10, #11 and #12 are always 2 words
long. Message #13 is always 3 words long. Message #1 is always 4
words long.
Message #1 is sent only by the CALLER, #3 only by the NEGOTIATION
MASTER, and #4 and #5 only by the NEGOTIATION SLAVE. Message #9 is
Cohen [Page 6]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
sent only by the ANSWERER. All the other control messages may be
sent by either party.
The last <HOW> which was both suggested by the NEGOTIATION MASTER
(in #3) and accepted by the NEGOTIATION SLAVE (in #4) for each
<WHAT> is assumed to be in use.
Cohen [Page 7]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
DEFINITION OF THE <WHAT> AND <HOW> NEGOTIATION TABLES:
<WHAT> <HOW>
1. VOCODING * 1. LPC
+ 2. CVSD
3. RELP
4. DELCO
2. SAMPLE PERIOD
(in microseconds) N. N (*150) (+62)
3. VERSION
* 1. V1 (see definition below)
+ 2. V2 (see definition below)
4. MAX MSG LENGTH (in bits)
NVP header included N. N (*976 and +976)
(32 bits) but not HOST/IMP
leader and not HOST/IMP padding
5. If LPC:
Degree N. For N coefficients (*10)
If CVSD:
Time Constant
(in milliseconds) N. N (+50)
6. Samples per Parcel N. N (*128) (+224)
7. If LPC:
Acoustic Coding * 1. SIMPLE (see below)
2. OPTIMIZED
8. If LPC:
Info Coding * 1. SIMPLE (see below)
2. OPTIMIZED
Cohen [Page 8]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
9. If LPC:
Pre-emphasis N. N (*58, for
1 - mu x [Z**-1] mu = 58/64 = 0.90625)
N = 64 x mu
10. If LPC:
Table-set N. N (*1)
See definition of Set #1
in Appendix 1
(* indicates recommended options for LPC)
(+ indicates recommended options for CVSD)
No parameter (<WHAT>) should be inquired about by the NEGOTIATION
MASTER if some option (<HOW>) for it has been previously accepted
by the NEGOTIATION SLAVE implicitly in the "VERSION". The purpose
of this restriction is to avoid a possible conflict between
individual parameters and the VERSION-option.
Version 1 (V1) is defined as:
1-1 LPC
2-150 150 microseconds sampling
3-1 V1
5-10 10 coefficients
6-128 128 samples per parcel
7-1 SIMPLE acoustic coding
8-1 SIMPLE information coding
9-58 mu = 58/64 = 0.90625
10-1 Tables set #1
Version 2 (V2) is defined as:
1-2 CVSD
2-62 62 microseconds sampling (16 KHz sampling)
3-2 V2
5-50 50 msec time constant
6-192 192 samples per parcel
Note that this defines every negotiated parameter, except MAX
MSG LENGTH.
SIMPLE and OPTIMIZED codings will be described below in Section
3.
All the negotiation is managed by the NEGOTIATION MASTER, who
decides how much negotiation is needed, and what to do in case
Cohen [Page 9]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
some discrepancy (incompatibility) is discovered: either to try
alternative options or to abort the connection. Upon completion
of successful negotiation, the NEGOTIATION MASTER sends either
#9 (RINGING) only if it is the ANSWERER and if this is an
initial connection, else it sends #6 (READY-FOR-DATA), and
probably inquires with #8 about the readiness of the other
party. The inquiries (#8) before the successful completion of
the negotiation are ignored. However, these inquiries after the
first RINGING (#9) and before the first READY (#6) are needed
to keep the ANSWERER ringing.
Note that the negotiation process can be shortened by using the
VERSION option, as shown in the examples that follow.
ON RENEGOTIATION
At any stage after links are agreed upon, either party might
request a RENEGOTIATION. If the request is approved by the other
party, either party might become the NEGOTIATION MASTER, depending
on the type of renegotiation request. When renegotiation starts,
no previously negotiated agreements (except LINK numbers) hold,
and all items have to be renegotiated from scratch. Note that
renegotiation may entirely replace the negotiation phase and
allows the CALLER to be the NEGOTIATION MASTER.
Upon issuance (or reception) of RENEGOTIATION REQUEST, all data
messages are ignored until the positive indication of the
successful completion of the renegotiation (#6).
After the completion of renegotiation, the frame-count (see the
section on MESSAGE-HEADER) may be reset to zero.
THE HEADER OF DATA MESSAGES
Data messages are the messages which contain vocoded speech. The
first 32 bits of each data message is the MESSAGE-HEADER, which
carries sequence and timing information as described below.
For each vocoding scheme a "FRAME" is defined as the transmission
interval (as agreed upon at the negotiation stage in <WHAT#6>).
Since this interval is defined by the number of samples, its
duration can be found by multiplying the sampling period <WHAT#2>
by the interval length (in samples) <WHAT#6>. For example, in V1
the sampling period is 150 microseconds and the transmission
interval is 128 samples, which yields:
128*150 microseconds = 19.2 milliseconds.
The data describing a FRAME is called a PARCEL. Each parcel has a
Cohen [Page 10]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
serial number. The first parcel created after the completion of
the negotiation (or every RENEGOTIATION) has the serial number
zero. Each message contains an integral number of parcels.
The serial number of the first parcel in the message is put in the
first 16 bits of the message and is referred to as the
MESSAGE-TIME-STAMP. Note that this time stamp is synchronized with
the data stream. Note also that these 16 bits are actually the
third word of the message, following the 2 words used as
IMP-to-HOST leader (see BBN Report 1822).
The next bit in the header is the WE-SKIPPED-PARCELS bit, which is
described later. The next 7 bits tell how many parcels there are
in the message; this number is called the COUNT, or the
PARCEL-COUNT.
Note that if message number N has the time stamp T(N) and the
count C(N), then T(N+1) must be greater than or equal to
T(N)+C(N). Usually T(N+1) = T(N)+C(N), unless the XMTR decided not
to send some parcels due to silence. If this happens then the
WE-SKIPPED-PARCELS bit is set to ONE, else it is set to ZERO.
Hence, if T(N+1) is found by the RCVR to be greater than T(N)+C(N)
and the WE-SKIPPED-PARCELS is zero, some message must be lost.
Note that by definition the time stamps on messages monotonically
increase, except for wrap-around.
The message header structure is illustrated by the following
diagram:
WORD 1 WORD 2 WORD 3 WORD 4
!................!................!................!................!...
!P000TTTTHHIIIIII!LLLLLLLLZZZZZZZZ!TTTTTTTTTTTTTTTT!WCCCCCCCSSSSSSSS!DDD
!................!................!................!^...............!...
!<--HOST/IMP-OR-IMP/HOST-LEADER-->!<--TIME-STAMP-->!^<COUNT><-SAVE->!<-D
^
WE-SKIPPED-PARCELS
P = PRIORITY (one bit = 1)
T = MESSAGE TYPE (4 bits = 0011)
L = link ("L" OR "K", 8 bits, greater than 337 octal)
D = data bits (from here to the end of the message)
ZZZZZZZZ = 8 ZERO bits
HHIIIIII = HOST (8 bits, destination or source)
CCCCCCC = parcel COUNT (7 bits)
SSSSSSSS = 8 bits saved for future applications
TTTTTTTTTTTTTTTT = TIME STAMP (16 bits)
Cohen [Page 11]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
The first parcel sent by either party after the NEGOTIATION or
RENEGOTIATION should have the serial number set to zero.
During silence periods, the XMTR might send a "6" or "7"
message periodically. If it does not do so, the RCVR might
interrogate the livelihood of the XMTR by sending periodically
"8" ("ARE-YOU-THERE?") or #10 (ECHO-REQUEST) messages.
Cohen [Page 12]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
3. THE LPC DATA PROTOCOL
The DATA sent at each transmission interval is called a PARCEL.
Network messages always contain an integral number of PARCELs.
There are two independent issues in the coding. One is, obviously,
the acoustic coding, i.e., which parameters have to be transmitted.
SIMPLE acoustic coding is sending all the parameters at every
transmission interval. OPTIMIZED acoustic coding sends only as little
as acoustically needed. DELCO is an example of OPTIMIZED acoustic
coding.
In this document only the format of the SIMPLE acoustic coding is
defined.
All the transmitted parameters are sent as pointers into agreed-upon
tables. These tables are defined as two lists of values. The
transmitter table {X(J)} is used in the following way: The value V is
coded as the code J if X(J-1) < V =< X(J). The receiver table {R(J)
is used to retrieve the value R(J) if the code J was received. X(-1)
is implicitly defined as minus-infinity, and X(Jmax) is explicitly
defined as plus-infinity.
For each parameter, {X(J)} and {R(J)} may be defined independently.
The second coding issue is the information coding technique. The
SIMPLE (information-wise) way of sending the information is to use
binary coding for the codes representing the parameters. The
OPTIMIZED way is to compute distributions for each parameter and to
define the appropriate coding. It is very probable that the PITCH and
GAIN will be decoded absolutely in the first PARCEL of each message,
and incrementally thereafter.
At present, only the SIMPLE (information-wise) coding is used.
The details of the LPC data protocol and its Tables-Set-#1 can be
found in Appendix 1.
Cohen [Page 13]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
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.
Cohen [Page 14]
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.
Cohen [Page 15]
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.
Cohen [Page 16]
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
Cohen [Page 18]
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.
Cohen [Page 20]
NWG/RFC 741 DC 22 Nov 77 42444
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).
Cohen [Page 21]
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
11 24 32 45 53 85
4711 8359 15175
12 25 33 47 54 87
4838 8596 15618
13 26 34 48 55 90
4969 8840 16075
14 27 35 50 56 93
5104 9092 16545
15 27 36 51 57 95
5242 9351 17029
16 28 37 53 58 98
5385 9618 17529
17 29 38 54 59 101
5533 9894 18043
18 30 39 56 60 104
5684 10177 18572
19 31 40 57 61 107
5841 10469 19118
20 32 41 59 62 111
6002 10770 19681
63 114
infinity
Cohen [Page 22]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
Note: This table has only 58 different intervals defined, since 5
values are repeated in the R(j) table.
* This value is the "Transmission Interval" (measured in samples)
as defined in item #6 of the NEGOTIATION.
Cohen [Page 23]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
THE GAIN TABLE (as of 9-17-75)
X(J) J R(J) X(J) J R(J)
0 225
0 0 16 245
20 266
1 20 17 289
22 315
2 24 18 342
26 372
3 28 19 404
30 439
4 33 20 478
36 519
5 39 21 565
42 614
6 46 22 667
50 725
7 54 23 789
59 857
8 64 24 932
70 1013
9 76 25 1101
83 1197
10 90 26 1301
98 1415
11 106 27 1538
116 1672
12 126 28 1818
137 1976
13 148 29 2148
161 2335
14 175 30 2539
191 2760
15 207 31 3000
255 infinity
Cohen [Page 24]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
INDEX7 TABLE (as of 9-23-74)
X(J) J R(J) X(J) J R(J) X(J) J R(J)
0 15800 27897
0 0 21 16151 42 28106
402 16500 28311
1 804 22 16846 43 28511
1206 17190 28707
2 1608 23 17531 44 28899
2009 17869 29086
3 2411 24 18205 45 29269
2811 18538 29448
4 3212 25 18868 46 29622
3612 19195 29792
5 4011 26 19520 47 29957
4410 19841 30118
6 4808 27 20160 48 30274
5205 20475 30425
7 5602 28 20788 49 30572
5998 21097 30715
8 6393 29 21403 50 30853
6787 21706 30986
9 7180 30 22006 51 31114
7571 22302 31238
10 7962 31 22595 52 31357
8351 22884 31471
11 8740 32 23170 53 31581
9127 23453 31686
12 9512 33 23732 54 31786
9896 24008 31881
13 10279 34 24279 55 31972
10660 24548 32058
14 11039 35 24812 56 32138
11417 25073 32214
15 11793 36 25330 57 32286
12167 25583 32352
16 12540 37 25833 58 32413
12910 26078 32470
17 13279 38 26320 59 32522
13646 26557 32568
18 14010 39 26791 60 32610
14373 27020 32647
19 14733 40 27246 61 32679
15091 27467 32706
20 15447 41 27684 62 32729
15800 27897 32746
63 32758
infinity
Cohen [Page 25]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
INDEX6 TABLE (as of 9-23-74)
X(J) J R(J) X(J) J R(J)
0 22595
0 0 16 23170
804 23732
1 1608 17 24279
2411 24812
2 3212 18 25330
4011 25833
3 4808 19 26320
5602 26791
4 6393 20 27246
7180 27684
5 7962 21 28106
8740 28511
6 9512 22 28899
10279 29269
7 11039 23 29622
11793 29957
8 12540 24 30274
13279 30572
9 14010 25 30853
14733 31114
10 15447 26 31357
16151 31581
11 16846 27 31786
17531 31972
12 18205 28 32138
18868 32286
13 19520 29 32413
20160 32522
14 20788 30 32610
21403 32679
15 22006 31 32729
22595 infinity
Cohen [Page 26]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
INDEX5 TABLE (as of 9-23-74)
X(J) J R(J) X(J) J R(J)
0 22006
0 0 8 23170
1608 24279
1 3212 9 25330
4808 26320
2 6393 10 27246
7962 28106
3 9512 11 28899
11039 29622
4 12540 12 30274
14010 30853
5 15447 13 31357
16846 31786
6 18205 14 32138
19520 32413
7 20788 15 32610
22006 infinity
Cohen [Page 27]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
APPENDIX 2
IMPLEMENTATION RECOMMENDATIONS
(1) It is recommended that the priority-bit be turned ON in the
HOST/IMP header.
(2) It is recommended that in all abbreviations, "R" be used for
Receiver and "X" for Transmitter.
(3) The following identifiers and values are recommended for
implementations:
SLNCTH 30 SILENCE-THRESHOLD.
Used for LONG-SILENCE definition. See below. Measured in the
same units as GAIN, in its X-table.
TBS 1.000 sec TIME-BEGIN-SILENCE.
LONG-SILENCE is declared if GAIN<SLNCTH for more than TBS.
TAS 0.500 sec TIME-AFTER-SILENCE.
A delay introduced by the receiver after the end of
LONG-SILENCE, before restarting the playback.
TES 0.150 sec TIME-END-SILENCE.
The amount of time the transmitter backs up at the end of a
LONG-SILENCE in order to ensure a smooth transition back to
speech.
TRI 2.000 sec TIME-RESPONSE-INITIAL.
Time for waiting for response for an initial call (#1 and #3).
The initial call is repeated every TRI until an answer arrives,
or until TRIGU expires.
TRIGU 20.000 sec TIME-RESPONSE-INITIAL-GIVEUP.
If no response to an initial call is received within TRIGU
after the FIRST initial call, the system gives up, assuming the
other system is down.
TRQ 1.000 sec TIME-RESPONSE-INQUIRY.
If no response to an inquiry (#8) is received within TRQ, the
inquiry is repeated.
Cohen [Page 28]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
TRQGU 10.000 sec TIME-RESPONSE-INQUIRY-GIVEUP.
If no response to an inquiry is received within TRQGU from the
FIRST inquiry, the system gives up, assuming the other system
is down.
TBDA 3.000 sec TIME-BETWEEN-DATA-ARRIVAL.
If no data arrives within TBDA, an INQUIRY (#8) is sent. This
repeats every TBDA.
TNR 2.000 sec TIME-NOT-READY.
If the other system is in the NOT-READY (#7) state for more
than TNR, an INQUIRY (#8) is sent. This repeats every TNR.
TNRGU 10.000 sec TIME-NOT-READY-GIVEUP.
If the other system is in the NOT-READY (#7) state for more
than TNRGU, then the system gives up, assuming the other
system is down.
TBIN 3.000 sec TIME-BUFFER-IN.
The input buffer size is equivalent to the time period TBIN
(and its size is the DATA-RATE multiplied by the period
TBIN). If the INPUT QUEUE ever gets to be longer than TBIN,
data is discarded.
TBOUT 3.000 sec TIME-BUFFER-OUT.
The output buffer size is equivalent to the time period TBOUT
(and its size is the DATA-RATE multiplied by the period
TBOUT). If the OUTPUT QUEUE ever gets to be longer than
TBOUT, data is discarded.
Cohen [Page 29]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
REFERENCES
Bolt Beranek & Newman, Inc., Report No. 1822, Interface Message
Processor: Specifications for the Interconnection of a Host and an
IMP.
NSC Note 42 (in progress).
NSC Note 36, Proposal for NSC-LPC Coding/Decoding Tables, by J. D.
Markel, Speech Communications Research Laboratory, Inc., July 20,
1974.
NSC Note 45, Everything You Always Wanted to Know about Gain, by E.
Randolph Cole, USC/Information Sciences Institute, October 11, 1974.
NSC Note 56, Nothing to Lose, but Lots to Gain, by John Makhoul and
Lynn Cosell, Bolt Beranek & Newman, Inc., March 10, 1975.
NSC Note 58, Gain Again, by Randy Cole, USC/Information Sciences
Institute, March 12, 1975.
Cohen [Page 30]