Processing of excitation in audio coding and decoding
In an apparatus and method, time-varying signals are processed and encoded via a frequency domain linear prediction (FDLP) scheme to arrive at an all-pole model. Residual signals resulted from the scheme are estimated and transformed into a time domain signal. Through the process of heterodyning, the time domain signal is frequency shifted toward the baseband level as a downshifted carrier signal. Quantized values of the all-pole model and the frequency transform of the downshifted carrier signal are packetized as encoded signals suitable for transmission or storage. To reconstruct the time-varying signals, the encoded signals are decoded. The decoding process is basically the reverse of the encoding process.
1. A method for encoding a time-varying signal, comprising:
partitioning said time-varying signal into a plurality of sub-band signals;
determining an envelope and a carrier portion for each of said sub-band signals;
frequency-shifting said carrier portion towards the baseband frequency of said time-varying signal as a down-shifted carrier signal;
selectively selecting values of said down-shifted carrier signal; and
including said selected values as encoded data of said time-varying signal.
2. The method as in claim 1 further comprising converting said time-varying signal as a discrete signal prior to encoding.
3. The method as in claim 1 further comprising transforming said time-varying signal into a frequency-domain transform, wherein said plurality of sub-band signals are selected from said frequency-domain transform of said time-varying signal.
4. The method as in claim 3 wherein said envelope and carrier portions are frequency-domain signals, said method further comprising transforming said carrier portion of said frequency-domain signals into a time-domain transform prior to frequency-shifting said carrier portion towards the baseband frequency.
5. A method for decoding a time-varying signal, comprising:
providing a plurality of sets of values corresponding to a plurality of sub-bands of said time-varying signal, said sets of values comprising envelope and carrier information of said time-varying signal;
identifying said carrier information from said plurality of sets of values as a plurality of carrier signals corresponding to said plurality of sub-bands;
frequency-shifting each of said plurality of carrier signals away from the baseband frequency of said time-varying signal as an up-shifted carrier signal; and
including said up-shifted carrier signal as decoded data of said time-varying signal.
6. The method as in claim 5 further comprising inverse-heterodyning each of said plurality of carrier signals as an up-shifted carrier signal.
7. The method as in claim 6 further comprising identifying said envelope information from said plurality of sets of values as a plurality of envelope signals corresponding to said plurality of sub-bands, and thereafter modulating said plurality of carrier signals by said plurality of envelope signals as a reconstructed version of said time-varying signal.
8. An apparatus for encoding a time-varying signal, comprising:
means for partitioning said time-varying signal into a plurality of sub-band signals;
means for determining an envelope portion and a carrier portion for each of said sub-band signals;
means for frequency-shifting said carrier portion towards the baseband frequency of said time-varying signal as a down-shifted carrier signal;
means for selectively selecting values of said down-shifted carrier signal; and
means for including said selected values as encoded data of said time-varying signal.
9. The apparatus as in claim 8 further comprising means for converting said time-varying signal as a discrete signal prior to encoding.
10. The apparatus as in claim 8 further comprising means for transforming said time-varying signal into a frequency-domain transform, wherein said plurality of sub-band signals are selected from said frequency-domain transform of said time-varying signal.
11. The apparatus as in claim 10 wherein said envelope and carrier portions are frequency-domain signals, said apparatus further comprising means for transforming said carrier portion of said frequency-domain signals into a time-domain transform prior to frequency-shifting said carrier portion towards the baseband frequency.
12. An apparatus for decoding a time-varying signal, comprising:
means for providing a plurality of sets of values corresponding to a plurality of sub-bands of said time-varying signal, said sets of values comprising envelope and carrier information of said time-varying signal;
means for identifying said carrier information from said plurality of sets of values as a plurality of carrier signals corresponding to said plurality of sub-bands;
means for frequency-shifting each of said plurality of carrier signals away from the baseband frequency of said time-varying signal as an up-shifted carrier signal; and
means for including said up-shifted carrier signal as decoded data of said time-varying signal.
13. The apparatus as in claim 12 further comprising means for inverse-heterodyning each of said plurality of carrier signals as an up-shifted carrier signal.
14. The apparatus as in claim 12 further comprising means for identifying said envelope information from said plurality of sets of values as a plurality of envelope signals corresponding to said plurality of sub-bands, and means for modulating said plurality of carrier signals by said plurality of envelope signals as a reconstructed version of said time-varying signal.
15. An apparatus for encoding a time-varying signal, comprising:
hardware encoder configured to partition said time-varying signal into a plurality of sub-band signals, determine an envelope and a carrier portion for each of said sub-band signals, frequency-shift said carrier portion towards the baseband frequency of said time-varying signal as a down-shifted carrier signal, and selectively select values of said down-shifted carrier signal; and
a hardware data packetizer connected to said hardware encoder for packetizing said selected values as part of encoded data of said time-varying signal.
16. The apparatus as in claim 15 further comprising a transmit circuit connected to said hardware data packetizer for sending said encoded data through a communication channel.
17. An apparatus for decoding a time-varying signal, comprising:
a hardware data depacketizer configured to provide a plurality of sets of values corresponding to a plurality of sub-bands of said time-varying signal, wherein said sets of values comprising envelope and carrier information of said time-varying signal, and further to identify said envelope and carrier information from said plurality of sets of values as a plurality of envelope and carrier signals corresponding to said plurality of sub-bands, frequency-shift each of said plurality of carrier signals away from the baseband frequency of said time-varying signal as an up-shifted carrier signal, and
a hardware decoder connected to said hardware data depacketizer, said hardware decoder being configured to transform said set of values into time-domain values.
18. A non-transitory computer program product, comprising:
a computer-readable medium physically embodied with computer-readable program code for:
partitioning said time-varying signal into a plurality of sub-band signals;
determining an envelope and a carrier portion for each of said sub-band signals;
frequency-shifting said carrier portion towards the baseband frequency of said time-varying signal as a down-shifted carrier signal;
selectively selecting values of said down-shifted carrier signal; and
including said selected values as encoded data of said time-varying signal.
19. The computer program product as in claim 18 further comprising computer-readable code for converting said time-varying signal as a discrete signal prior to encoding.
20. The computer program product as in claim 18 further comprising computer-readable code for transforming said time-varying signal into a frequency-domain transform, wherein said plurality of sub-band signals are selected from said frequency-domain transform of said time-varying signal.
21. The computer program product as in claim 20 further comprising computer-readable code for transforming said carrier portion of said frequency-domain signals into a time-domain transform prior to frequency-shifting said carrier portion towards the baseband frequency.
22. A non-transitory computer program product, comprising:
a computer-readable medium physically embodied with computer-readable program code for:
providing a plurality of sets of values corresponding to a plurality of sub-bands of said time-varying signal, said sets of values comprising envelope and carrier information of said time-varying signal;
identifying said carrier information from said plurality of sets of values as a plurality of carrier signals corresponding to said plurality of sub-bands;
frequency-shifting each of said plurality of carrier signals away from the baseband frequency of said time-varying signal as an up-shifted carrier signal; and
including said up-shifted carrier signal as decoded data of said time-varying signal.
23. The computer product as in claim 22 further comprising computer-readable code for inverse-heterodyning each of said plurality of carrier signals as an up-shifted carrier signal.
24. The computer product as in claim 22 further comprising computer-readable code for identifying said envelope information from said plurality of sets of values as a plurality of envelope signals corresponding to said plurality of sub-bands, and thereafter modulating said plurality of carrier signals by said plurality of envelope signals as a reconstructed version of said time-varying signal.
25. An apparatus encoding a time-varying signal, comprising:
a processor configured to execute a set of instructions; and
a memory, coupled to the processor, embodying the set of instructions that when executed by the processor cause the processor to: encode said time-varying signal into a plurality of sub-band signals, determine an envelope and a carrier portion of each of said sub-band signals, frequency-shift said carrier portion towards the baseband frequency of said time-varying signal as a down-shifted carrier signal, and selectively select values of said down-shifted carrier signal, and packetize the selected values as part of encoded data of said time-varying signal.
26. The apparatus of claim 25 , further comprising a transmit circuit connected to the processor for sending said encoded data through a communication channel.
27. An apparatus for decoding a time-varying signal, comprising:
a processor configured to execute a set of instructions; and
a memory, coupled to the processor, embodying the set of instructions that when executed by the processor cause the processor to: de-packetize a sets of values corresponding to a plurality of sub-bands of said time-varying signal, wherein said sets of values comprise envelope and carrier information of said time-varying signal, and further to identify said envelope and carrier information from said plurality sets of values as a plurality of envelope and carrier signals corresponding to said plurality of sub-bands, frequency-shift each of said plurality of carrier signals away from the baseband frequency of said time-varying signal as an up-shifted carrier signal, and a decoder connected to said data de-packetizer, said decoder being configured to transform said set of values into time-domain values.