Speech compression and decompression apparatuses and methods providing scalable bandwidth structure

A speech decompression apparatus that decompresses a speech signal that is compressed into a scalable bandwidth structure, comprising:

• a narrowband speech decompressor receiving a low-band speech packet, decompressing the low-band speech packet, and outputting a decompressed narrow low-band speech signal;
• a high-band speech decompression unit receiving a high-band speech packet, decompressing the high-band speech packet, and outputting a decompressed high-band speech signal;
• and
• an adder adding the decompressed narrow low-band speech signal and the decompressed high-band speech signal and outputting a result of the adding as a decompressed wideband speech signal,
• wherein the high-band speech packet includes a quantized RMS value, a predictor type index used when the speech signal is compressed, and a quantized DFT coefficient, and the high-band speech decompression unit self-calculates and uses a DFT coefficient phase when the quantized DET coefficient is an inverse DFT, and
• wherein the DFT coefficient phase is obtained for each DFT coefficient as follows:
• νi(0)[m]=νi(−1)[m]+wcN,
• θi[m]=νi(0)[m]+Ψ[m]
• where θi[m] is the DFT coefficient phase, m is an index of the quantized DFT coefficient, i is a frequency band index, and νi(0)[m] and νi(−1)[m] correspond to a current subframe and a previous subframe, respectively.

A speech decompression apparatus that decompresses a speech signal that is compressed into a scalable bandwidth structure, comprising:

• a narrowband speech decompressor receiving a low-band speech packet, decompressing the low-band speech packet, and outputting a decompressed narrow low-band speech signal;
• a high-band speech decompression unit receiving a high-band speech packet, decompressing the high-band speech packet, and outputting a decompressed high-band speech signal;
• and
• an adder adding the decompressed narrow low-band speech signal and the decompressed high-band speech signal and outputting a result of the adding as a decompressed wideband speech signal,
• wherein the high-band speech packet includes an index of a quantized RMS value, a predictor type index used when the speech signal is compressed, and an index of a quantized DFT coefficient, and
• wherein the high-band speech decompression unit includes:
• an inverse quantizer selecting an inverse quantizer from among a plurality of inverse quantizers using the predictor type index and calculating a quantized prediction error value using the selected inverse quantizer and the index of the quantized RMS value;
• a prediction selector selecting a predictor from among a plurality of predictors in response to the predictor type index and calculating a quantized RMS value that corresponds to the quantized predictor error value using the selected predictor;
• a codebook outputting a normalized DFT coefficient magnitude that corresponds to the index of the quantized DFT coefficient;
• a multiplier multiplying the quantized RMS value by the normalized OFT coefficient magnitude;
• a DFT phase calculator calculating a DFT coefficient phase corresponding to the index of the quantized DFT coefficient;
• a inverse DFT unit obtaining a time domain signal for each of the frequency bands using the DFT coefficient magnitude output from the multiplier and the DFT coefficient phase output from the OFT phase calculator;
• a filter bank obtaining a speech signal for each of the frequency bands using the time domain signal and outputting the speech signal;
• and
• an adder adding the speech signals for each of the frequency bands and outputting a result of the adding as a decompressed high-band speech signal that corresponds to the compressed high-band speech packet.

A speech compression apparatus comprising:

• a first band-transform unit transforming a wideband speech signal to a narrowband low-band speech signal;
• a narrowband speech compressor compressing the narrowband low-band speech signal and outputting a result of the compressing as a low-band speech packet;
• a decompression unit decompressing the low-band speech packet and obtaining a decompressed wideband low-band speech signal;
• an error detection unit detecting an error signal that corresponds to a difference between the wideband speech signal and the decompressed wideband low-band speech signal;
• and
• a high-band speech compression unit compressing the error signal and a high-band speech signal of the wideband speech signal and outputting the result of the compressing as a high-band speech packet, wherein the error detection unit comprises:
• a first filter bank filtering the wideband speech signal in a first specified frequency band and outputting a first filtered signal;
• a first masking unit generating a first masked signal for the wideband speech signal derived from the first filtered signal;
• a second filter bank filtering the decompressed wideband low-band speech signal in a second specified frequency band and outputting a second filtered signal;
• a second masking unit generating a second masked signal for the decompressed wideband low-band speech signal derived from the second filtered signal;
• and
• an inter-signal masking unit performing inter-signal masking on the first and second masked signals.