Hybrid speech coding and system

• US 7,222,070 B1
• Filed: 09/22/2000
• Issued: 05/22/2007
• Est. Priority Date: 09/22/1999
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: McCree, Alan V., Stachurski, Jacek
• Primary Examiner(s): ARMSTRONG, ANGELA A
• Application Number:
  US09/668,396
• Time in Patent Office: 2,433 Days
• Field of Search: 704/205, 704/207, 704/208, 704/216, 704/222, 704/223
• US Class Current: 704/207
• CPC Class Codes: G10L 19/04 using predictive techniques
• CPC Class Codes: G10L 19/097 using prototype waveform decomposition or prototype waveform interpolative [PWI] coders
• CPC Class Codes: G10L 19/20 using sound class specific coding, hybrid encoders or object based coding

Abstract

Linear predictive speech coding system with classification of frames and a hybrid coder using both waveform coding and parametric coding for different classes of frames. Phase alignment for a parametric coder aligns synthesized speech frames with adjacent waveform coder synthesized frames. Zero phase alignment of speech prior to waveform coding aligns synthesized speech frames of a waveform coder with frames synthesized with a parametric coder. Inter-frame interpolation of LP coefficients suppresses artifacts in resultant synthesized speech frames.

Claims

1. A hybrid speech encoder, comprising:

(a) a linear prediction, pitch and, voicing analyzer;

(b) a parametric encoder coupled to said analyzer; and

(c) a waveform encoder coupled to said analyzer;

(d) wherein said analyzer classifies frames with voice activity as one of strongly-voiced, weakly-voiced, or unvoiced and said parametric encoder encodes strongly-voiced frames and said waveform encoder encodes both weakly-voiced and unvoiced frames, and wherein said waveform encoder includes both a zero-phase equalization filter plus a pitch-prediction filter for weakly-voiced frames and said parametric encoder omits a zero-phase equalization filter.

2. The encoder of claim 1, wherein:

(a) said zero-phase equalization filter has coefficients determined by said analyzer.

3. A hybrid speech decoder, comprising:

(a) a linear prediction synthesizer;

(b) a parametric decoder coupled to said synthesizer; and

(c) a waveform decoder coupled to said synthesizer;

(d) wherein said waveform decoder decodes zero-phase equalized plus pitch-predicted weakly-voiced frames and also decodes unvoiced frames and said parametric decoder decodes non-zero-phase-equalized strongly-voiced frames.