SIST ETS 300 395-3:1999

• Abstract:

  Selection and specification of the speech codec for TETRA voice plus data standard

• Status: Published
• Publication Date: 31-Oct-1999
• ICS: 33.070.10 - Terrestrial Trunked Radio (TETRA)
• Technical Committee: RES - Radio equipment and systems
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Nov-1999
• Due Date: 01-Nov-1999
• Completion Date: 01-Nov-1999
• Mandate: T-300
• Ref Project: ETSI ETS 300 395-3 ed.1 (1997-05) - Terrestrial Trunked Radio (TETRA); Speech codec for full-rate traffic channel; Part 3: Specific operating features

SIST ETS 300 395-3:1999 is the Slovenian adoption of ETS 300 395-3 Edition 1 from ETSI. It covers the specific operating features of the TETRA speech codec for the full-rate traffic channel, with a focus on how encoder and decoder control, signalling, and optional functions behave in practice.

This part is aimed at people implementing or testing TETRA voice plus data equipment. It complements the codec definition itself, which is handled in the associated codec part.

What does SIST ETS 300 395-3:1999 specify?

SIST ETS 300 395-3:1999 specifies the functions associated with the TETRA speech codec, except for the codec algorithm itself. In practice, it tells implementers how the speech encoder and decoder control units should behave, how signalling data is carried in stolen half slots, and how optional features such as comfort noise and frame stealing are handled.

Clause 4 covers the speech encoder, clause 5 covers the speech decoder, and clause 6 defines the signalling data block format. Annex A is informative and gives implementation guidance for optional features.

Annex	What it covers
A	Implementation of optional features such as Speech importance, Voice Activity Detection (VAD), Discontinuous Transmission (DTX), Comfort Noise Frame (CNF) handling, Missing Frame Generation (MFG), BFI setting, U-plane frame stealing, receiver muting, and response to U-plane signalling

What are the key requirements of SIST ETS 300 395-3:1999?

The standard defines how the encoder and decoder control functions interact with the codec and with the TETRA signalling path. The practical effect is that equipment must handle homing, frame stealing, comfort noise, missing frames, and test mode in a predictable way so different vendors’ equipment can interwork.

Encoder behaviour

Clause 4 requires the speech encoder to accept 16-bit uniform PCM at 8 000 samples per second and to output coded speech frames through the encryption interface or directly to the MAC when encryption is not used. This matters because the encoder must match the TETRA frame structure and routing messages used in the air interface.

Clause 4.1 defines an encoder homing frame as 240 identical samples with the value 0x0008. When such a frame is aligned with the encoder frame boundary, the encoder is reset to its home state. This gives a repeatable reset condition for maintenance and conformance testing.

Speech control functions

Clause 4.2 requires a Speech importance function that labels each frame as NO_IMPORTANCE, LOW, MEDIUM, or HIGH. In practice, this helps a system decide which speech frames can be stolen first if capacity is needed elsewhere.

Clause 4.3 covers comfort noise. A CNF has the same format as a normal speech frame, and if DTX is used on the uplink, the system must still send CNF or other data often enough to keep the receiving base station from dropping the connection. That is the basic control rule behind uninterrupted service during silence periods.

Clause 4.4 defines signalling messages used with frame stealing: SPEECH_ON, SPEECH_OFF, CNF_COMMAND, and MUTE. Clause 6 gives the half-slot data format for these messages. This is what lets the MAC and U-plane coordinate active speech, comfort noise, and muting.

Decoder behaviour and missing frames

Clause 5 requires the decoder to output synthesized speech as 16-bit uniform PCM at 8 000 samples per second. Clause 5.2 defines decoder homing, using a fixed 137-bit decoder homing frame. This provides a known reset response for the receive side.

Clause 5.3 and 5.4 cover Missing Frame Generation (MFG) and missing frame substitution. They are used when half slots are lost because of radio link failure, frame stealing, or DTX. The Bad Frame Indicator (BFI) tells the decoder when concealment should be applied.

Test mode and signalling format

Clause 4.5 and 5.5 define codec conformance test mode. In that mode, frame stealing is disabled, encryption and decryption are disabled, and the codec behaves in a controlled way for testing. This is important because test results depend on the codec not altering the frames in ways the test does not expect.

Clause 6 also defines the signalling data block format inside a stolen half slot, including the HSSE, SHSI, signalling message, and signalling data fields. This gives implementers the exact structure needed for U-plane signalling.

What terms does SIST ETS 300 395-3:1999 define?

• BFI (Bad Frame Indicator) - a flag that identifies a bad received frame so the decoder can apply concealment.
• CNF (Comfort Noise Frame) - a frame used to create comfort noise at the receiver during silence periods.
• DTX (Discontinuous Transmission) - a method that reduces transmission during silence while keeping the call alive.
• LTP (Long Term Predictor) - a codec parameter used in speech coding and comfort noise computation.
• MAC (Medium Access Control) - the layer that handles access to the radio channel and carries the TMD messages.
• PCM (Pulse Coded Modulation) - the 16-bit speech sample format used at the encoder input and decoder output.
• RMS (Root Mean Square) - a measure that may be used when calculating speech importance.
• VAD (Voice Activity Detector) - a function that detects active speech for DTX-related behaviour.

Who uses SIST ETS 300 395-3:1999?

SIST ETS 300 395-3:1999 is used by TETRA equipment designers, radio system integrators, and conformance testers. It is relevant when implementing speech encoding and decoding, U-plane signalling, frame stealing, comfort noise, DTX, and encryption interfaces in TETRA voice plus data systems.

Which standards are used with SIST ETS 300 395-3:1999?

• ETS 300 395-1 - gives the general description of speech functions in the TETRA full-rate codec family.
• ETS 300 395-2 - defines the codec itself; this part builds on that codec definition.
• ETS 300 392-2 - provides common TETRA definitions and abbreviations, and the air interface context.
• ETS 300 392-7 - defines the security-related interface used for encoded speech and control information.
• ETS 300 395-4 - the foreword identifies this as the codec conformance testing part of the same series.

What does the SIST ETS 300 395-3:1999 document contain?

The document contains clause text plus figures that summarize the encoder and decoder operating features. It also contains the decoder homing frame bit pattern in a table, the signalling message coding table, and the signalling data block formats used for stolen half slots.

Annex A adds implementation guidance rather than requirements. It discusses practical approaches for Speech importance calculation, VAD, DTX, CNF computation, MFG, BFI setting, U-plane frame stealing, receiver muting, and handling of U-plane signalling.

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Radijska oprema in sistemi (RES) - Vseevropski sistem snopovnega radia (TETRA) - Prizemni snopovni radio (TETRA) - Govorni kodek za kanal s polno hitrostjo - 3. del: Posebne obratovalne lastnostiTerrestrial Trunked Radio (TETRA); Speech codec for full-rate traffic channel; Part 3: Specific operating features33.070.10Prizemni snopovni radio (TETRA)Terrestrial Trunked Radio (TETRA)33.020Telekomunikacije na splošnoTelecommunications in generalICS:Ta slovenski standard je istoveten z:ETS 300 395-3 E13SIST ETS 300 395-3:1999en01-MXOLM19993SIST ETS 300 395-3:1999SLOVENSKI
STANDARD
EUROPEANETS 300 395-3TELECOMMUNICATIONMay 1997STANDARDSource: ETSI TC-RESReference: DE/RES-06002-3ICS:33.020Key words:TETRA, CODECRadio Equipment and Systems (RES);Trans-European Trunked Radio (TETRA);Speech codec for full-rate traffic channel;Part 3: Specific operating featuresETSIEuropean Telecommunications Standards InstituteETSI SecretariatPostal address: F-06921 Sophia Antipolis CEDEX - FRANCEOffice address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCEX.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: [e-mail].: [phone] - Fax: [phone]Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and theforegoing restriction extend to reproduction in all media.© European Telecommunications Standards Institute 1997. All rights reserved.SIST ETS 300 395-3:1999

Page 2ETS 300 395-3: May 1997Whilst every care has been taken in the preparation and publication of this document, errors in content,typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to"ETSI Editing and Committee Support Dept." at the address shown on the title page.SIST ETS 300 395-3:1999

Page 3ETS 300 395-3: May 1997ContentsForeword.51Scope.72Normative references.73Definitions and abbreviations.73.1Definitions.73.2Abbreviations.74Speech encoder.84.1Encoder homing function.94.1.1Definition of encoder homing frame.94.1.2Encoder homing.94.2Speech importance function.94.3Comfort noise function.94.4Frame stealing function.94.5Test mode functions.104.6Encryption interface.105Speech decoder.115.1Encryption interface.115.2Decoder homing function.125.2.1Definition of decoder homing frame.125.2.2Decoder homing.125.3Missing frame generation.125.4Missing frame substitution.125.5Test mode functions.126Signalling Data Block Format.13Annex A (informative):Implementation of optional features.14A.1Speech importance calculation.14A.2Voice Activity Detection (VAD).14A.3Discontinuous Transmission (DTX).14A.4CNF computation.14A.5Missing Frame Generation (MFG).14A.5.1Error concealment.14A.5.2Comfort noise generation.14A.6Setting BFI.15A.7U-plane frame stealing.15A.8Receiver muting.15A.9Response to U-plane signalling.15History.16SIST ETS 300 395-3:1999

Page 4ETS 300 395-3: May 1997Blank pageSIST ETS 300 395-3:1999

Page 5ETS 300 395-3: May 1997ForewordThis European Telecommunication Standard (ETS) has been produced by the Radio Equipment System(RES) Technical Committee of the European Telecommunications Standards Institute (ETSI).This ETS consists of four parts as follows:Part 1:"General description of speech functions";Part 2:"TETRA codec";Part 3:"Specific operating features";Part 4:"Codec conformance testing".Transposition datesDate of adoption:2 May 1997Date of latest announcement of this ETS (doa):31 August 1997Date of latest publication of new National Standardor endorsement of this ETS (dop/e):28 February 1998Date of withdrawal of any conflicting National Standard (dow):28 February 1998SIST ETS 300 395-3:1999

Page 6ETS 300 395-3: May 1997Blank pageSIST ETS 300 395-3:1999

Page 7ETS 300 395-3: May 19971ScopeThis European Telecommunication Standard (ETS) describes all the functions associated with the TETRAspeech codec, excepted the specification of the codec by itself which is entirely defined inETS 300 395-2 [2].Clause 4 of this ETS provides a description of the functions associated with the speech encoder, whileclause 5 is its counterpart for the speech decoder.Clause 6 describes the contents and the format of the signalling data block included in a stolen framewhen used for transferring information relevant to the codec in a U-plane signalling message.In addition, annex A (informative) provides indications and preferred solutions for the implementation ofoptional features.2Normative referencesThis ETS incorporates, by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text and the publications are listedhereafter. For dated references, subsequent amendments to, or revisions of, any of these publicationsapply to this ETS only when incorporated in it by amendment or revision. For undated references the latestedition of the publication referred to applies.[1]ETS 300 395-1 (1995): "Radio Equipment and Systems (RES); Trans-EuropeanTrunked Radio (TETRA) system; Speech codec for full-rate traffic channel;Part 1: General description of speech functions".[2]ETS 300 395-2 (1995): "Radio Equipment and Systems (RES); Trans-EuropeanTrunked Radio (TETRA) system; Speech codec for full-rate traffic channel;Part 2: TETRA codec".[3]ETS 300 392-2 (1995): "Radio Equipment and Systems (RES); Trans-EuropeanTrunked Radio (TETRA) system; Voice plus Data; Part 2: Air Interface".[4]ETS 300 392-7 (1995): "Radio Equipment and Systems (RES); Trans-EuropeanTrunked Radio (TETRA) system; Voice plus Data; Part 7: Security".3Definitions and abbreviations3.1DefinitionsRefer to ETS 300 392-2 [3], clause 3 for common TETRA definitions.3.2AbbreviationsFor the purposes of this ETS, the following abbreviations apply:BFIBad Frame IndicatorCNFComfort Noise FrameDTXDiscontinuous TransmissionLTPLong Term PredictorMACMedium Access ControlPCMPulse Coded ModulationRMSRoot Mean SquareVADVoice Activity DetectorRefer to ETS 300 392-2 [3] clause 3 for common TETRA abbreviations.SIST ETS 300 395-3:1999

Page 8ETS 300 395-3: May 19974Speech encoderA diagram of the speech encoder and associated functions is given in figure 1. A more general overview isgiven in ETS 300 395-1 [1]. The speech encoder is defined in ETS 300 395-2 [2] and the other functionsform the speech encoder control unit. The speech encoder control unit shall have access to all the internaldata and functions of the speech encoder (including the input speech).COMFORT NOISEFUNCTIONTEST MODEFUNCTIONS1235Reset4ENCODER HOMINGFUNCTIONSPEECH IMPORTANCEFUNCTIONSpeech Encoder ControlFRAME STEALINGFUNCTIONENCRYPTIONINTERFACESPEECH ENCODER1)16-bit uniform PCM, 8 000 samples/s2)Encoded speech frame 30 ms, 137 bits/frame3)Encoded speech frame in "TMD_UNITDATA_request" message4)Stolen indication in "TMD_REPORT_indication" message5)Test mode controlFigure 1: Overview of speech encoder specific operating featuresThe speech encoder as defined in ETS 300 395-2 [2] shall receive speech in the form of 16-bit uniform PCMat a rate of 8 000 samples per second.The coded data corresponding to each 30 ms speech frame shall be output from the speech encoder controlunit via the encryption interface to the encryption unit (or directly to the MAC if encryption is not used). Theinterfaces with the encryption unit, namely interface points 3 and 4 in figure 1, shall be as defined inETS 300 392-7 [4], clause 7. Message "TMD_UNITDATA_ request" is the means of conveying half-slotsfrom the U-plane to the MAC, while "TMD_REPORT_indication" enables the MAC to pass control informationto the U-plane.Comfort noise parameters may be generated and their presence in the coded speech data shall be indicatedby a U-plane signalling message conveyed using the frame stealing mechanism.A speech importance indication shall be provided.The presence of a homing sequence in the input speech shall be recognized and the encoder reset to adefined state.All functions necessary to support conformance testing shall be implemented.SIST ETS 300 395-3:1999

Page 9ETS 300 395-3: May 1997An appropriate U_device destination address shall be set for each half slot of coded speech data to allowcorrect routing at the receiver.4.1Encoder homing function4.1.1Definition of encoder homing frameThe encoder homing frame shall consist of 240 identical samples (corresponding to a 30 ms speech frame),each 16 bits long with the value 0x0008.NOTE:0x0008 is a number represented in hexadecimal notation.4.1.2Encoder homingWhenever the speech encoder receives at its input an encoder homing frame exactly aligned with itsinternal speech frame segmentation, the following events shall take place:Step 1:the speech encoder performs its normal operation and produces a speech parameter frameat its output which is in general unknown;Step 2:the speech encoder shall be reset and placed in its home state by executing the resetfunctions "Init_Coder_Tetra( )" and "Init_Pre_Process( )" as defined in ETS 300 395-2 [2];Step 3:the speech encoder is now in its home state and any further consecutive encoder homingframes shall result in an output speech parameter frame identical to the decoder homingframe.Applying a sequence of N encoder homing frames to the speech encoder input shall cause at least N-1decoder homing frames at the output of the speech encoder control unit.4.2Speech importance functionThis function shall compute a
...

SLOVENSKI STANDARD
01-november-1999
Radijska oprema in sistemi (RES) - Vseevropski sistem snopovnega radia (TETRA)
- Prizemni snopovni radio (TETRA) - Govorni kodek za kanal s polno hitrostjo - 3.
del: Posebne obratovalne lastnosti
Terrestrial Trunked Radio (TETRA); Speech codec for full-rate traffic channel; Part 3:
Specific operating features
Ta slovenski standard je istoveten z: ETS 300 395-3 Edition 1
ICS:
33.070.10 Prizemni snopovni radio Terrestrial Trunked Radio
(TETRA) (TETRA)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 395-3
TELECOMMUNICATION May 1997
STANDARD
Source: ETSI TC-RES Reference: DE/RES-06002-3
ICS: 33.020
Key words: TETRA, CODEC
Radio Equipment and Systems (RES);
Trans-European Trunked Radio (TETRA);
Speech codec for full-rate traffic channel;
Part 3: Specific operating features
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: [e-mail]
Tel.: [phone] - Fax: [phone]
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1997. All rights reserved.

Page 2
ETS 300 395-3: May 1997
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

Page 3
ETS 300 395-3: May 1997
Contents
Foreword.5
1 Scope .7
2 Normative references.7
3 Definitions and abbreviations .7
3.1 Definitions .7
3.2 Abbreviations .7
4 Speech encoder .8
4.1 Encoder homing function .9
4.1.1 Definition of encoder homing frame .9
4.1.2 Encoder homing .9
4.2 Speech importance function .9
4.3 Comfort noise function.9
4.4 Frame stealing function .9
4.5 Test mode functions .10
4.6 Encryption interface .10
5 Speech decoder .11
5.1 Encryption interface .11
5.2 Decoder homing function.12
5.2.1 Definition of decoder homing frame .12
5.2.2 Decoder homing.12
5.3 Missing frame generation .12
5.4 Missing frame substitution .12
5.5 Test mode functions .12
6 Signalling Data Block Format.13
Annex A (informative): Implementation of optional features .14
A.1 Speech importance calculation .14
A.2 Voice Activity Detection (VAD) .14
A.3 Discontinuous Transmission (DTX) .14
A.4 CNF computation .14
A.5 Missing Frame Generation (MFG) .14
A.5.1 Error concealment .14
A.5.2 Comfort noise generation .14
A.6 Setting BFI.15
A.7 U-plane frame stealing .15
A.8 Receiver muting .15
A.9 Response to U-plane signalling.15
History.16

Page 4
ETS 300 395-3: May 1997
Blank page
Page 5
ETS 300 395-3: May 1997
Foreword
This European Telecommunication Standard (ETS) has been produced by the Radio Equipment System
(RES) Technical Committee of the European Telecommunications Standards Institute (ETSI).
This ETS consists of four parts as follows:
Part 1: "General description of speech functions";
Part 2: "TETRA codec";
Part 3: "Specific operating features";
Part 4: "Codec conformance testing".
Transposition dates
Date of adoption: 2 May 1997
Date of latest announcement of this ETS (doa): 31 August 1997
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 28 February 1998
Date of withdrawal of any conflicting National Standard (dow): 28 February 1998

Page 6
ETS 300 395-3: May 1997
Blank page
Page 7
ETS 300 395-3: May 1997
1 Scope
This European Telecommunication Standard (ETS) describes all the functions associated with the TETRA
speech codec, excepted the specification of the codec by itself which is entirely defined in
ETS 300 395-2 [2].
Clause 4 of this ETS provides a description of the functions associated with the speech encoder, while
clause 5 is its counterpart for the speech decoder.
Clause 6 describes the contents and the format of the signalling data block included in a stolen frame
when used for transferring information relevant to the codec in a U-plane signalling message.
In addition, annex A (informative) provides indications and preferred solutions for the implementation of
optional features.
2 Normative references
This ETS incorporates, by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to, or revisions of, any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references the latest
edition of the publication referred to applies.
[1] ETS 300 395-1 (1995): "Radio Equipment and Systems (RES); Trans-European
Trunked Radio (TETRA) system; Speech codec for full-rate traffic channel;
Part 1: General description of speech functions".
[2] ETS 300 395-2 (1995): "Radio Equipment and Systems (RES); Trans-European
Trunked Radio (TETRA) system; Speech codec for full-rate traffic channel;
Part 2: TETRA codec".
[3] ETS 300 392-2 (1995): "Radio Equipment and Systems (RES); Trans-European
Trunked Radio (TETRA) system; Voice plus Data; Part 2: Air Interface".
[4] ETS 300 392-7 (1995): "Radio Equipment and Systems (RES); Trans-European
Trunked Radio (TETRA) system; Voice plus Data; Part 7: Security".
3 Definitions and abbreviations
3.1 Definitions
Refer to ETS 300 392-2 [3], clause 3 for common TETRA definitions.
3.2 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
BFI Bad Frame Indicator
CNF Comfort Noise Frame
DTX Discontinuous Transmission
LTP Long Term Predictor
MAC Medium Access Control
PCM Pulse Coded Modulation
RMS Root Mean Square
VAD Voice Activity Detector
Refer to ETS 300 392-2 [3] clause 3 for common TETRA abbreviations.

Page 8
ETS 300 395-3: May 1997
4 Speech encoder
A diagram of the speech encoder and associated functions is given in figure 1. A more general overview is
given in ETS 300 395-1 [1]. The speech encoder is defined in ETS 300 395-2 [2] and the other functions
form the speech encoder control unit. The speech encoder control unit shall have access to all the internal
data and functions of the speech encoder (including the input speech).
SPEECH ENCODER
Reset
TEST MODE ENCODER HOMING
FUNCTIONS FUNCTION
FRAME STEALING COMFORT NOISE SPEECH IMPORTANCE
FUNCTION FUNCTION FUNCTION
ENCRYPTION
INTERFACE
Speech Encoder Control
1) 16-bit uniform PCM, 8 000 samples/s
2) Encoded speech frame 30 ms, 137 bits/frame
3) Encoded speech frame in "TMD_UNITDATA_request" message
4) Stolen indication in "TMD_REPORT_indication" message
5) Test mode control
Figure 1: Overview of speech encoder specific operating features
The speech encoder as defined in ETS 300 395-2 [2] shall receive speech in the form of 16-bit uniform PCM
at a rate of 8 000 samples per second.
The coded data corresponding to each 30 ms speech frame shall be output from the speech encoder control
unit via the encryption interface to the encryption unit (or directly to the MAC if encryption is not used). The
interfaces with the encryption unit, namely interface points 3 and 4 in figure 1, shall be as defined in
ETS 300 392-7 [4], clause 7. Message "TMD_UNITDATA_ request" is the means of conveying half-slots
from the U-plane to the MAC, while "TMD_REPORT_indication" enables the MAC to pass control information
to the U-plane.
Comfort noise parameters may be generated and their presence in the coded speech data shall be indicated
by a U-plane signalling message conveyed using the frame stealing mechanism.
A speech importance indication shall be provided.
The presence of a homing sequence in the input speech shall be recognized and the encoder reset to a
defined state.
All functions necessary to support conformance testing shall be implemented.

Page 9
ETS 300 395-3: May 1997
An appropriate U_device destination address shall be set for each half slot of coded speech data to allow
correct routing at the receiver.
4.1 Encoder homing function
4.1.1 Definition of encoder homing frame
The encoder homing frame shall consist of 240 identical samples (corresponding to a 30 ms speech frame),
each 16 bits long with the value 0x0008.
NOTE: 0x0008 is a number represented in hexadecimal notation.
4.1.2 Encoder homing
Whenever the speech encoder receives at its input an encoder homing frame exactly aligned with its
internal speech frame segmentation, the following events shall take place:
Step 1: the speech encoder performs its normal operation and produces a speech parameter frame
at its output which is in general unknown;
Step 2: the speech encoder shall be reset and placed in its home state by executing the reset
functions "Init_Coder_Tetra( )" and "Init_Pre_Process( )" as defined in ETS 300 395-2 [2];
Step 3: the speech encoder is now in its home state and any further consecutive encoder homing
frames shall result in an output speech parameter frame identical to the decoder homing
frame.
Applying a sequence of N encoder homing frames to the speech encoder input shall cause at least N-1
decoder homing frames at the output of the speech encoder control unit.
4.2 Speech imp
...