# US 8,543,388 B2 · Efficient speech stream conversion

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- Number: US 8,543,388 B2
- Document ID: US8543388B2
- Status: Granted
- Kind: B2
- Application number: 12/095,709
- Filed: 2005-11-30
- Published: 2010-09-02
- Granted: 2013-09-24
- Earliest claimed: 2005-11-30
- Assignees: Telefonaktiebolaget LM Ericsson (publ)
- Applicants: Nicklas Sandgren; Jonas Svedberg
- Inventors: Nicklas Sandgren; Jonas Svedberg
- Web page: https://patentgrep.com/patent/US8543388B2

## CPC

- G10L 19/012: Comfort noise or silence coding
- G10L 19/173: {Transcoding, i.e. converting between two coded representations avoiding cascaded coding-decoding}
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

Speech frames of a first speech coding scheme are utilized as speech frames of a second speech coding scheme, where the speech coding schemes use similar core compression schemes for the speech frames, preferably bit stream compatible. An occurrence of a state mismatch in an energy parameter between the first speech coding scheme and the second speech coding scheme is identified, preferably either by determining an occurrence of a predetermined speech evolution, such as a speech type transition, e.g. an onset of speech following a period of speech inactivity, or by tentative decoding of the energy parameter in the two encoding schemes followed by a comparison. Subsequently, the energy parameter in at least one frame of the second speech coding scheme following the occurrence of the state mismatch is adjusted. The present invention also presents transcoders and communications systems providing such transcoding functionality.

## Claims

### Claim 1

Method for speech transcoding from a first speech coding scheme to a second speech coding scheme using similar core compression schemes for speech frames, comprising the steps of:
utilizing speech frames of said first speech coding scheme as speech frames of said second speech coding scheme, wherein said first speech coding scheme and said second speech coding scheme have a same sub-frame structure and are bit stream compatible for frames comprising coded speech;
identifying an occurrence of state mismatch in an energy parameter between said first speech coding scheme and said second speech coding scheme; and
adjusting said energy parameter following said occurrence of state mismatch.

### Claim 2 (depends on 1)

Method according to claim 1, wherein said step of adjusting comprises adjusting said energy parameter in at least one frame following said occurrence of state mismatch in frames of said second speech coding scheme.

### Claim 3 (depends on 1)

Method according to claim 1, wherein said core compression schemes of said first speech coding scheme and said second speech coding scheme are bit stream compatible for frames containing coded speech.

### Claim 4 (depends on 1)

Method according to claim 1, wherein said step of identifying comprises the step of determining an occurrence of a predetermined speech evolution.

### Claim 5 (depends on 4)

Method according to claim 4, wherein said predetermined speech evolution is a speech type transition.

### Claim 6 (depends on 5)

Method according to claim 5, wherein said predetermined speech evolution is an onset of speech following a period of speech inactivity.

### Claim 7 (depends on 1)

Method according to claim 1, wherein said step of identifying in turn comprises the steps of:
decoding a first energy parameter of speech encoded by said first speech coding scheme;
decoding of a second energy parameter of said speech using said second speech coding scheme; and
comparing said first energy parameter and said second energy parameter.

### Claim 8 (depends on 1)

Method according to claim 1, wherein said step of adjusting comprises the step of changing said energy parameter by a predetermined factor.

### Claim 9 (depends on 8)

Method according to claim 8, wherein said predetermined factor is a predetermined factor in the index domain.

### Claim 10 (depends on 8)

Method according to claim 8, wherein said step of adjusting comprises the step of changing said energy parameter according to a comparison between said first energy parameter of speech encoded by said first speech coding scheme and said second energy parameter of speech encoded by said second speech coding scheme.

### Claim 11 (depends on 1)

Method according to claim 1, wherein said step of adjusting is performed for the first n subframe after said occurrence of state mismatch, where n>0.

### Claim 12 (depends on 10)

Method according to claim 10, wherein said step of adjusting is performed continuously for every subframe until said state mismatch is negligible.

### Claim 13 (depends on 1)

Method according to claim 1, wherein said step of adjusting comprises the step of changing said energy parameter based on an estimate based on comfort noise energy during frames preceding said occurrence of state mismatch.

### Claim 14 (depends on 1)

Method according to claim 1, wherein said step of adjusting comprises the step of changing a quantization state of said energy parameter based on external energy information.

### Claim 15 (depends on 1)

Method according to claim 1, comprising the further step of converting silence description parameters in silence description frames of said first speech coding scheme to silence description parameters in silence description frames of said second speech coding scheme.

### Claim 16 (depends on 1)

Method according to claim 1, wherein said first speech coding scheme is GSM-EFR and said second speech coding scheme is AMR-12.2.

### Claim 17 (depends on 16)

Method according to claim 16, wherein said step of adjusting comprises the step of reducing said energy parameter index by a factor 2n, where n is an integer >0.

### Claim 18 (depends on 16)

Method according to claim 16, wherein said step of adjusting comprises the step of setting said energy parameter to zero, whereby said first subframe after said occurrence of state mismatch is suppressed.

### Claim 19 (depends on 16)

Method according to claim 16, comprising the step of:
converting a first GSM-EFR silence description frame to an AMR SID_FIRST frame.

### Claim 20 (depends on 19)

Method according to claim 19, comprising the further step of:
utilizing silence description parameters of a latest received GSM-EFR silence description frame as a basis for silence description parameters of an AMR SID_UPDATE frame, whenever an AMR SID_UPDATE frame is to be sent.

### Claim 21 (depends on 20)

Method according to claim 20, comprising the further step of:
filtering an energy parameter of said AMR SID_UPDATE frame.

### Claim 22 (depends on 1)

Method according to claim 1, wherein said first speech coding scheme is AMR-12.2 and said second speech coding scheme is GSM-EFR.

### Claim 23 (depends on 22)

Method according to claim 22, comprising the step of:
converting an AMR SID_FIRST frame to a first GSM-EFR silence description frame.

### Claim 24 (depends on 23)

Method according to claim 23, wherein the step of converting in turn comprises the steps of:
estimating silence descriptor parameters for an incoming AMR SID_FIRST frame; and
quantizing said estimated silence descriptor parameters into a first GSM-EFR silence description.

### Claim 25 (depends on 23)

Method according to claim 23, comprising the further step of:
storing received silence description parameters from an AMR SID_UPDATE frame;
keeping a local TAF state;
determining when a new GSM-EFR silence description frame is to be sent from said TAF state;
quantizing the latest of said stored received silence description parameters to be included in said new GSM-EFR silence description frame.

### Claim 26

Speech transcoder, transcoding frames from a first speech coding scheme to a second speech coding scheme using similar core compression schemes for speech frames, comprising:
means for utilizing speech frames of said first speech coding scheme as speech frames of said second speech coding scheme, wherein said first speech coding scheme and said second speech coding scheme have a same sub-frame structure and are bit stream compatible for frames comprising coded speech;
means for identifying an occurrence of state mismatch in an energy parameter between said first speech coding scheme and said second speech coding scheme; and
means for adjusting said energy parameter following said occurrence of state mismatch, connected to said means for identifying.

### Claim 27 (depends on 26)

Speech transcoder according to claim 26, wherein said means for adjusting is arranged for adjusting said energy parameter in at least one frame following said occurrence of state mismatch in frames of said second speech coding scheme.

### Claim 28 (depends on 26)

Speech transcoder according to claim 26, wherein said core compression schemes of said first speech coding scheme and said second speech coding scheme are bit stream compatible for frames containing coded speech.

### Claim 29 (depends on 26)

Speech transcoder according to claim 26, wherein said means for identifying comprises the means for determining an occurrence of a predetermined speech evolution.

### Claim 30 (depends on 29)

Speech transcoder according to claim 29, wherein said predetermined speech evolution is a speech type transition.

### Claim 31 (depends on 30)

Speech transcoder according to claim 30, wherein said predetermined speech evolution is an onset of speech following a period of speech inactivity.

### Claim 32 (depends on 26)

Speech transcoder according to claim 26, wherein said means for identifying in turn comprises:
decoder of a first energy parameter of speech encoded by said first speech coding scheme;
decoder of a second energy parameter of said speech using said second speech coding scheme; and
comparator, connected to said decoder of said first energy parameter and said decoder of said second energy parameter, for comparing said first energy parameter and said second energy parameter.

### Claim 33 (depends on 26)

Speech transcoder according to claim 26, wherein said means for adjusting comprises means for changing said energy parameter by a predetermined factor.

### Claim 34 (depends on 33)

Speech transcoder according to claim 33, wherein said predetermined factor is a predetermined factor in the index domain.

### Claim 35 (depends on 32)

Speech transcoder according to claim 32, wherein said means for adjusting is arranged for changing said energy parameter according to a comparison between said first energy parameter of speech encoded by said first speech coding scheme and said second energy parameter of speech encoded by said second speech coding scheme.

### Claim 36 (depends on 33)

Speech transcoder according to claim 33, wherein said means for adjusting is arranged to influence a first subframe after said occurrence of state mismatch.

### Claim 37 (depends on 35)

Speech transcoder according to claim 35, wherein said means for adjusting is arranged for operating continuously for every subframe until said state mismatch is negligible.

### Claim 38 (depends on 26)

Speech transcoder according to claim 26, wherein said means for adjusting comprises means for estimating an energy parameter based on comfort noise energy during frames preceding said occurrence of state mismatch and means for changing said energy parameter based on said estimate.

### Claim 39 (depends on 26)

Speech transcoder according to claim 26, further comprising means for converting silence description parameters in silence description frames of said first speech coding scheme to silence description parameters in silence description frames of said second speech coding scheme.

### Claim 40 (depends on 26)

GSM-EFR to AMR-12.2 speech transcoder according to claim 26.

### Claim 41 (depends on 40)

GSM-EFR to AMR-12.2 speech transcoder according to claim 40, wherein said means for adjusting is arranged for reducing said energy parameter index by a factor 2n, where n is an integer >0.

### Claim 42 (depends on 40)

GSM-EFR to AMR-12.2 speech transcoder according to claim 40, wherein said means for adjusting is arranged for setting said energy parameter to zero, whereby said first subframe after said occurrence of state mismatch is suppressed.

### Claim 43 (depends on 40)

GSM-EFR-to-AMR 12.2 speech transcoder according to claim 40, comprising means for converting a first GSM-EFR silence description frame to an AMR SID_FIRST frame.

### Claim 44 (depends on 43)

GSM-EFR-to-AMR 12.2 speech transcoder according to claim 43, further comprising means for utilizing silence description parameters of a latest received GSM-EFR silence description frame as a basis for silence description parameters of an AMR SID_UPDATE frame, whenever an AMR SID_UPDATE frame is to be sent.

### Claim 45 (depends on 44)

GSM-EFR-to-AMR 12.2 speech transcoder according to claim 44, comprising a filter for an energy parameter of said AMR SID_UPDATE frame.

### Claim 46 (depends on 26)

AMR 12.2-to-GSM-EFR speech transcoder according to claim 26.

### Claim 47 (depends on 46)

AMR 12.2-to-GSM-EFR speech transcoder according to claim 46, comprising means for converting an AMR SID_FIRST frame to a first GSM-EFR silence description frame.

### Claim 48 (depends on 47)

AMR 12.2-to-GSM-EFR speech transcoder according to claim 47, wherein said means for converting is arranged to estimate silence descriptor parameters for an incoming AMR SID_FIRST frame and to quantize said estimated silence descriptor parameters into a first GSM-EFR silence description.

### Claim 49 (depends on 47)

AMR 12.2-to-GSM-EFR speech transcoder according to claim 47, further comprising:
storage of received silence description parameters from an AMR SID_UPDATE frame;
means for keeping a local TAF state;
means for determining when a new GSM-EFR silence description frame is to be sent from said TAF state;
means for quantizing the latest of said stored received silence description parameters to be included in said new GSM-EFR silence description frame.

### Claim 50 (depends on 26)

Telecommunication system comprising a speech transcoder according to claim 26.