Apparatus and method of code conversion and recording medium that records program for computer to execute the method

• US 20060222084A1
• Filed: 03/16/2006
• Published: 10/05/2006
• Est. Priority Date: 03/29/2005
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Murashima, Atsushi
• Granted Patent: US 8,374,852 B2
• Time in Patent Office: Days
• US Class Current: 375/242
• CPC Class Codes: G10L 19/173 Transcoding, i.e. converting between two coded representations avoiding cascaded coding-decoding
• CPC Class Codes: G10L 25/78 Detection of presence or absence of voice signals switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10

Abstract

Disclosed is a code conversion method to convert a first code sequence conforming to a first speech coding scheme into a second code sequence conforming to a second speech coding scheme. The method includes the following steps. The first step discriminates whether the first code sequence corresponds to a speech part or to a non-speech part, and generates a numerical value that indicates the discrimination result as a control flag. The second step converts the first code sequence into the second code sequence and outputs said second code sequence, when the value of the control flag corresponds to the speech part. The third step outputs the second code sequence that corresponds to the value of the control flag, when the value of the control flag corresponds to the non-speech part.

Claims

1. A code conversion method for converting a first code sequence conforming to a first speech coding scheme into a second code sequence conforming to a second speech coding scheme, said method comprising the steps of:

(A) discriminating whether said first code sequence corresponds to a speech part or to a non-speech part and generating a value that indicates the discrimination result as a control flag;

(B) converting said first code sequence into said second code sequence and outputting this code sequence, when the value of said control flag corresponds to the speech part; and

(C) outputting the second code sequence that corresponds to the value of said control flag, when the value of the control flag corresponds to the non-speech part.

2. The method as claimed in claim 1, wherein

said step (A) generats said control flag by using information contained in said first code sequence.

3. The method as claimed in claim 2, wherein

said step (A) generates said control flag, on the basis of frame type information contained in a frame within said first code sequence.

4. The method as claimed in claim 2, wherein

said step (A) generates said control flag, on the basis of a frame size contained in a frame within said first code sequence.

5. The method as claimed in claim 4, wherein

said frame size is represented by a size of payload in this frame.

6. The method as claimed in claim 1, wherein

said step (A) includes the steps of:

(A1) generating a decoded speech signal from said first code sequence with a first decoding method; and

(A2) discriminating whether the first code sequence that generates said control flag corresponds to the speech part or to the non-speech part, on the basis of said decoded speech signal and generating said control flag.

7. The method as claimed in claim 1, wherein

said step (C) outputs the second code sequence that corresponds to said control flag from one or more pre-stored second code sequences that correspond to the non-speech part.

8. The method as claimed in claim 1, wherein

said step (B) includes:

(B1) generating a decoded speech signal from said first code sequence with a first decoding method, when the value of said control flag corresponds to the speech part; and

(B2) re-encoding said decoded speech signal with a second encoding method and generating said second code sequence.

9. The method as claimed in claim 1, wherein

said first speech coding scheme and said second speech coding scheme are identical.

10. The method as claimed in claim 9, wherein

said Step (B) outputs said first code sequence as said second code sequence when the value of said control flag corresponds to said speech part.

11. The method as claimed in claim 1, wherein

said step (C) outputs a second code sequence corresponding to a predetermined signal or an assigned signal from the outside, when said value of said control flag indicates said non-speech part.

13. The apparatus as claimed in claim 10, wherein

said discrimination unit generates said control flag by using information contained in said first code sequence.

14. The apparatus as claimed in claim 13, wherein

said discrimination unit generates said control flag, on the basis of frame type information contained in a frame within said first code sequence.

15. The apparatus as claimed in claim 13, wherein

said discrimination unit generates said control flag, on the basis of a frame size contained in a frame within said first code sequence.

16. The apparatus as claimed in claim 13, wherein

said frame size is represented by a size of payload in this frame.

12. Code conversion apparatus for converting a first code sequence conforming to a first speech coding scheme into a second code sequence conforming to a second speech coding scheme, said apparatus comprising:

a discrimination unit that discriminates whether said first code sequence corresponds to a speech part or to a non-speech part and generates a value that indicates the discrimination result as a control flag;

a speech part conversion unit that converts said first code sequence into said second code sequence and outputs this code sequence, when the value of said control flag corresponds to the speech part; and

a non-speech part generating unit that outputs the second code sequence that corresponds to the value of said control flag, when the value of the control flag corresponds to the non-speech part.

17. The apparatus as claimed in claim 12, wherein

said discrimination unit includes:

a decoder that generates a decoded speech signal from said first code sequence with a first decoding method; and

a speech detection circuit that discriminates whether the first code sequence corresponds to the speech part or to the non-speech part on the basis of said decoded speech signal and outputs said control flag.

18. In the apparatus as claimed in claim 12, wherein said non-speech part generating unit generates the second code sequence that corresponds to said control flag from one or more pre-stored second code sequences that correspond to the non-speech part.

19. The apparatus as claimed in claim 12, wherein

said speech part conversion unit includes:

a decoder that generates a decoded speech signal from said first code sequence with a first decoding method, when the value of said control flag corresponds to the speech part; and

a re-encoder that re-encodes said decoded speech signal with a second encoding method and generates said second code sequence.

20. The apparatus as claimed in claim 12, wherein

said first speech coding scheme and said second speech coding scheme are identical.

21. The apparatus as claimed in claim 20, wherein

said non-speech part generating unit outputs said first code sequence as said second code sequence when the value of said control flag corresponds to said speech part.

22. The apparatus as claimed in claim 12, wherein

said speech part conversion unit outputs said second code sequence corresponding to a predetermined signal or an assigned signal from the outside, when said value of said control flag indicates said non-speech part.

29. The recording medium as claimed in claim 19, wherein said step (C) is a step for generating the second code sequence that corresponds to said control flag from one or more pre-stored second code sequences that correspond to the non-speech part.

23. A recording medium that records a program for a computer to execute a code conversion method for converting a first code sequence conforming to a first speech coding scheme into a second code sequence conforming to a second speech coding scheme, said program comprising the steps of:

(A) discriminating whether said first code sequence corresponds to a speech part or to a non-speech part and generating a value that indicates the discrimination result as a control flag;

(B) converting said first code sequence into said second code sequence and outputting this code sequence, when the value of said control flag corresponds to the speech part; and

(C) outputting the second code sequence that corresponds to the value of said control flag, when the value of the control flag corresponds to the non-speech part.

24. The recording medium as claimed in claim 23, wherein said step (A) generates said control flag by using information contained in said first code sequence.

25. The recording medium as claimed in claim 24, wherein said step (A) generates said control flag, on the basis of frame type information contained in a frame within said first code sequence.

26. The recording medium as claimed in claim 24, wherein said step (A) is a step for generating said control flag, on the basis of a frame size contained in a frame within said first code sequence.

27. The recording medium as claimed in claim 26, wherein said frame size is represented by a size of payload in this frame.

28. The recording medium as claimed in claim 23, wherein said step (A) includes the steps of:

(A1) generating a decoded speech signal from said first code sequence with a first decoding method; and

(A2) discriminating whether the first code sequence corresponds to the speech part or to the non-speech part, on the basis of said decoded speech signal and outputting said control flag.

30. The recording medium as claimed in claim 23, wherein said step (B) includes:

(B1) generating a decoded speech signal from said first code sequence with a first decoding method, when the value of said control flag corresponds to the speech part; and

(B2) re-encoding said decoded speech signal with a second encoding method and generating said second code sequence.

31. The recording medium as claimed in claim 23, wherein said first speech coding scheme and said second speech coding scheme are identical.

32. The recording medium as claimed in claim 31, wherein said Step (B) outputs said first code sequence as said second code sequence when the value of said control flag corresponds to said speech part.

33. The recording medium as claimed in claim 23, wherein said step (C) outputs said second code sequence corresponding to a predetermined signal or an assigned signal from the outside, when said value of said control flag indicates said non-speech part.