Adaptive audio signal source vector quantization device and adaptive audio signal source vector quantization method that search for pitch period based on variable resolution
An adaptive sound source vector quantization device includes a first pitch cycle instructor, a search range calculator, and a second pitch cycle instructor. The first pitch cycle instructor successively instructs pitch cycle search candidates in a predetermined search range having a search resolution which transits over a predetermined pitch cycle candidate for the first sub-frame. The search range calculator calculates a predetermined range before and after the pitch cycle of the first sub-frame as the pitch cycle search range for the second sub-frame, if the predetermined range includes the predetermined pitch cycle search candidate. In the predetermined range, the search resolution transits over a boundary defined by the predetermined pitch cycle. The second pitch cycle instructor successively instructs the pitch cycle search candidates in the search range for the second sub-frame.
1. An adaptive excitation vector quantization apparatus that searches for a pitch period in a fixed range for a first subframe of two subframes, the two subframes being provided by dividing a frame, searches for a pitch period in a second subframe in a range determined by a result of comparison between a searched pitch period in a first subframe and a predetermined threshold, and outputs information about the searched pitch periods as quantization data, the apparatus comprising:
a first pitch period search processor that searches for a first pitch period in the first subframe by changing resolution with respect to a boundary of the predetermined threshold;
a calculation processor that calculates a pitch period search range and a search resolution in the second subframe based on the first pitch period determined in the first subframe and the predetermined threshold; and
a second pitch period search processor that searches for a second pitch period in the second subframe by changing resolution based on the search resolution calculated by the calculation processor in the pitch period search range.
2. An adaptive excitation vector quantization method, executed by a processor, of searching for a pitch period in a fixed range for a first subframe of two subframes, the two subframes being provided by dividing a frame, searching for a pitch period in a second subframe in a range determined by a result of comparison between a searched pitch period in a first subframe and a predetermined threshold and outputting information about the searched pitch periods as quantization data, the method comprising:
searching for a first pitch period in the first subframe by changing resolution with respect to a boundary of the predetermined threshold;
calculating a pitch period search range and a search resolution in the second subframe based on the first pitch period determined in the first subframe and the predetermined threshold; and
searching for a second pitch period in the second subframe by changing resolution based on the calculated search resolution in the pitch period search range.
3. The adaptive excitation vector quantization apparatus according to claim 1 , wherein the search resolution calculated by the calculation processor comprises a first resolution and a second resolution in the pitch period search range, and the second pitch period search processor changes resolution from the first resolution to the second resolution in the pitch period search range.
4. The adaptive excitation vector quantization method according to claim 2 , wherein the calculated search resolution comprises a first resolution and a second resolution in the pitch period search range, and the searching for the second pitch period changes resolution from the first resolution to the second resolution in the pitch period search range.