Transceiver for selecting a source coder based on signal distortion estimate

• US 6,499,008 B2
• Filed: 05/21/1999
• Issued: 12/24/2002
• Est. Priority Date: 05/26/1998
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Miet, Gilles
• Primary Examiner(s): SMITS, TALIVALDIS IVARS
• Application Number:
  US09/316,776
• Publication Number:
  US 20020069075A1
• Time in Patent Office: 1,313 Days
• Field of Search: 704/200.1, 704/219, 704/220, 704/221
• US Class Current: 704/200.1
• CPC Class Codes: G10L 19/18 Vocoders using multiple modes

Abstract

A radio signal transceiver receiving at its input a speech signal and producing an output signal at a given output rate, the speech signal having undergone a source coding intended to sufficiently compress the input signal to obtain the desired output rate while an acceptable distortion ratio is maintained. In order to improve the compromise of transmission quality of the speech signal and transmission rate by selecting the optimum coder from the available coders, the transceiver comprises a measuring device for measuring the distortion of the output signal of a coder and a check circuit for comparing the estimated distortion with set values and deriving therefrom the optimum coder for the measured distortion.

Claims

1. A digital signal transceiver, comprising a transmitting part and a receiving part, the transmitting part receiving at its input an original speech signal and delivering a compressed speech signal on its output, the transceiver comprising:

source coder means including a plurality of source coders for compressing said speech signal and delivering the compressed signal of only one source coder of said plurality of source coders at a time and at a given output rate, said compressed signal having a measurable distortion, and said one source coder being a currently operating source coder,

calculation means for forming an estimate of the distortion of the compressed signal of the currently operating source coder,

check means for comparing said estimate with set values and, dependent upon the result of such comparison, selecting one of the source coders for delivering the compressed signal.

2. A transceiver as claimed in claim 1, wherein the source coder delivers an internal residual error signal, characterized in that said calculation means use said error signal for estimating said distortion.

3. A transceiver as claimed in claim 1, characterized in that the calculation means comprise:

inverse source decoder means co-operating with the source coder means for producing a decoded signal based on said compressed signal,

means for comparing the decoded signal with the original signal to produce a residual error signal, and

means for processing the residual error signal to derive said estimate therefrom.

4. A transceiver as claimed in claim 1, the receiving part comprising a plurality of decoders compatible with said source coders, characterized in that the transceiver comprises control means co-operating with said check means for automatically selecting from the plurality of decoders a decoder that is compatible with the source coder selected by said check means.

5. Telephony equipment comprising a transceiver as claimed in claim 1, characterized in that it is in conformity with a digital telecommunications standard.

6. A digital telecommunications system for exchanging speech signals with telephony equipment as claimed in claim 5.

7. A transceiver as claimed in claim 1 wherein the check means comprise a memory which stores the set values, wherein each set value corresponds to a respective coder of said plurality of coders.

8. A transceiver as claimed in claim 1 wherein the source coder means delivers to the calculation means a single internal residual error signal corresponding to the distortion of the compressed signal of the single one of the source coders currently operative, and the calculation means use said single internal residual error signal to estimate the distortion of the compressed signal.

9. A transceiver as claimed in claim 1 wherein, in the selection means, each original signal undergoes only one source coding test for the selection of the optimum source coder of the plurality of source coders.

10. A transceiver as claimed in claim 1 wherein, if the distortion estimate is within predetermined acceptable values, the same one source coder is selected, and otherwise another source coder is selected corresponding to the distortion estimate as related to the set values.

11. A digital signal transmission process comprising the following steps:

a receiving step for receiving an original speech signal,

a source coding step among a plurality of selectable coding steps, said source coding step being a currently operating step of compressing said original speech signal and at a given time delivering a compressed signal at a given output rate, said compressed signal having a measurable distortion,

a selection step of selecting a source coder from a plurality of coders for realizing the source coding step, the selection step comprising;

a calculation sub-step for forming an estimate of the distortion of the currently compressed signal, and

a check sub-step for comparing the estimate with set values and selecting the source coder as a function of the result of said comparison.

12. A process as claimed in claim 11, with the source coder delivering an internal residual error signal, characterized in that said residual error signal is used in the calculation sub-step for estimating the distortion of the compressed signal.

13. The process as claimed in claim 12 wherein, in the check sub-step, the distortion estimate is compared with set values stored in a digital memory, and

wherein each set value corresponds to a respective coder of said plurality of coders.

14. A process as claimed in claim 11, characterized in that the calculation sub-step comprises:

an inverse decoding step for producing a decoded signal based on said compressed signal,

a step of comparing the original speech signal with said decoded signal to obtain a residual error, and

a step of processing the residual error to obtain said estimate.

15. A digital signal reception process comprising a source decoding step for decoding a compressed signal via a transmission method as claimed in claim 11, characterized in that the process comprises a step of the automatic selection of a decoder from a plurality of available decoders as a function of said selected source coder.