Voice encoding device, voice decoding device, recording medium for recording program for realizing voice encoding/decoding and mobile communication device

• US 6,421,638 B2
• Filed: 12/05/2000
• Issued: 07/16/2002
• Est. Priority Date: 08/02/1996
• Status: Expired due to Term

• Current Assignee: III Holdings 12, LLC (Intellectual Ventures LLC)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Morii, Toshiyuki, Ehara, Hiroyuki
• Primary Examiner(s): Banks-Harold, Marsha D.
• Assistant Examiner(s): Lerner, Martin
• Application Number:
  US09/729,420
• Publication Number:
  US 20010003812A1
• Time in Patent Office: 588 Days
• Field of Search: 704/206, 704/207, 704/219, 704/221, 704/223
• US Class Current: 704/207
• CPC Class Codes: G10L 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders
• CPC Class Codes: G10L 2019/0005 Multi-stage vector quantisation

Abstract

The present invention intends to enhance a sound quality of a sound source generating portion in a CELP type voice encoding device and a CELP type voice decoding device. A pitch peak position of an adaptive code vector is obtained by a pitch peak position calculator 12, a window for emphasizing an amplitude of the pitch peak position is prepared by an amplitude emphasizing window generator 13, and an amplitude of a noise code vector corresponding to the pitch peak position is emphasized by an amplitude emphasizing window unit 16. Alternatively, pulse search positions are determined in such a manner that they become dense in a pitch peak position vicinity and coarse in the other portions. Based on the determined search positions, a pulse position searching is performed. Alternatively, the pitch peak position and pitch cycle information in the immediately previous sub-frame and the pitch cycle information in the present sub-frame are used to backward adapt and switch a sound source constitution. Sound quality is thus enhanced, while an influence of a transmission line error is inhibited from being propagated.

Claims

1. A CELP type voice encoding device which performs a voice encoding process for each sub-frame having a predetermined time length, determines whether or not a phase in the present sub-frame and a phase in the immediately previous sub-frame are continuous, and structure of a sound source to be used is switched from one to another depending on the result of the determination as to continuousness.

2. The CELP type voice encoding device as claimed in claim 1 wherein a pitch peak position in the immediately previous sub-frame, a pitch cycle in the immediately previous sub-frame and a pitch cycle of the present sub-frame are used to predict a pitch peak position in the present sub-frame, and by determining whether or not the pitch peak position in the present sub-frame obtained through the prediction is close to the pitch peak position which is obtained only from data in the present sub-frame, it is determined whether or not the phase in the immediately previous sub-frame and the phase in the present sub-frame are continuous, and according to a determination result, encoding process methods of said sound source are switched from one to another.

3. The CELP type voice encoding device as claimed in claim 1 which performs a phase adaptation process for the noise code book when it is determined that the phase in the immediately previous sub-frame and the phase in the present sub-frame are continuous and which does not perform the phase adaptation process for the noise code book when it is determined that the phase in the immediately previous sub-frame and the phase in the present sub-frame are not continuous.

4. A voice encoding method which performs a voice encoding process for each sub-frame having a predetermined time length, and wherein the voice encoding device determines whether or not a phase in the present sub-frame and a phase in the immediately previous sub-frame are continuous and switches a sound source in the case where it is determined that the phases are continuous, and structure of a sound source to be used is switched from one to another depending on the result of the determination as to continuousness.

5. The voice encoding method as claimed in claim 4 wherein a pitch peak position in the immediately previous sub-frame, a pitch cycle in the immediately previous sub-frame and a pitch cycle of the present sub-frame are used to predict a pitch peak position in the present sub-frame, and by determining whether or not the pitch peak position in the present sub-frame obtained through the prediction is close to the pitch peak position which is obtained only from data in the present sub-frame, it is determined whether or not the phase in the immediately previous sub-frame and the phase in the present sub-frame are continuous, and according to a determination result, encoding process methods of said sound source are switched from one to another.

6. The voice encoding method as claimed in claim 4 which performs a phase adaptation process for the noise code book when it is determined that the phase in the immediately previous sub-frame and the phase in the present sub-frame are continuous and which does not perform the phase adaptation process for the noise code book when it is determined that the phase in the immediately previous sub-frame and the phase in the present sub-frame are not continuous.

7. The voice encoding method as claimed in claim 6 wherein as said phase adaptation process, a pulse position searching is performed densely in the pitch peak vicinity while the pulse position search is performed coarsely in the portions other than the pitch peak vicinity, and a pulse sound source is applied in a noise sound source.

8. A CELP type voice decoding device which performs a voice decoding process for each sub-frame having a predetermined time length, determines whether or not a phase in the present sub-frame and a phase in the immediately previous sub-frame are continuous and switches a sound source in the case where it is determined that the phases are continuous, and structure of a sound source to be used is switched from one to another depending on the result of the determination as to continuousness.

9. The CELP type voice decoding device as claimed in claim 8 wherein a pitch peak position in the immediately previous sub-frame, a pitch cycle in the immediately previous sub-frame and a pitch cycle of the present sub-frame are used to predict a pitch peak position in the present sub-frame, and by determining whether or not the pitch peak position in the present sub-frame obtained through the prediction is close to the pitch peak position which is obtained only from data in the present sub-frame, it is determined whether or not the phase in the immediately previous sub-frame and the phase in the present sub-frame are continuous, and according to a determination result, encoding process methods of said sound source are switched from one to another.

10. The CELP type voice decoding device as claimed in claim 8 which performs a phase adaptation process for the noise code book when it is determined that the phase in the immediately previous sub-frame and the phase in the present sub-frame are continuous and which does not perform the phase adaptation process for the noise code book when it is determined that the phase in the immediately previous sub-frame and the phase in the present sub-frame are not continuous.

11. The CELP type voice decoding device as claimed in claim 10 wherein as said phase adaptation process, a pulse sound source is applied in a noise sound source in such a manner that pulse positions are dense in the pitch peak vicinity while the pulse positions are coarse in the portions other than the pitch peak vicinity.

12. A voice decoding method which performs a voice decoding process for each sub-frame having a predetermined time length, and wherein it is determined whether or not a phase in the present sub-frame and a phase in the immediately previous sub-frame are continuous, and structure of a sound source to be used is switched from one to another depending on the result of the determination as to continuousness.

13. The voice decoding method as claimed in claim 12 wherein a pitch peak position in the immediately previous sub-frame, a pitch cycle in the immediately previous sub-frame and a pitch cycle of the present sub-frame are used to predict a pitch peak position in the present sub-frame, and by determining whether or not the pitch peak position in the present sub-frame obtained through the prediction is close to the pitch peak position which is obtained only from data in the present sub-frame, it is determined whether or not the phase in the immediately previous sub-frame and the phase in the present sub-frame are continuous, and according to a determination result, encoding process methods of said sound source are switched from one to another.

14. The voice decoding method as claimed in claim 12 which performs a phase adaptation process for the noise code book when it is determined that the phase in the immediately previous sub-frame and the phase in the present sub-frame are continuous and which does not perform the phase adaptation process for the noise code book when it is determined that the phase in the immediately previous sub-frame and the phase in the present sub-frame are not continuous.

15. The voice decoding method as claimed in claim 14, wherein as said phase adaptation process, a pulse sound source is applied in a noise sound source in such a manner that pulse positions are dense in the pitch peak vicinity while the pulse positions are coarse in the portions other than the pitch peak vicinity.