Dual-transform coding of audio signals

An audio signal and encoding technology, applied in the field of audio signal encoding and decoding

Active Publication Date: 2008-04-23
HEWLETT PACKARD DEV CO LP
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Problems solved by technology

Although this method enables high-quality audio to be obtained over the existing telephone network, it generally requires ISDN service from the telephone company, which is more expensive than typical narrowband telephone service

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  • Dual-transform coding of audio signals
  • Dual-transform coding of audio signals
  • Dual-transform coding of audio signals

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Embodiment Construction

[0033] Various embodiments of the present invention extend and improve the performance of audio signal processing with innovative encoders and decoders. Broadly speaking, encoding processing includes transform processing, quantization processing, and encoding processing. Various embodiments of the invention make improvements in all three processes.

[0034] In most prior art audio signal processing, audio signal frames have a fixed length. The shorter the frame length, the lower the latency. For high frequencies, shorter frame lengths also provide better temporal resolution and better performance. However, short frames provide poor frequency resolution. Conversely, the longer the frame length, the longer the delay. However, at low frequencies, longer frames provide better frequency resolution and better performance at distinguishing tonal harmonics. In a compromise solution, the frame length is generally in the range of 20 ms, which is also the frame length adopted in the...

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Abstract

Methods, devices, and systems for coding and decoding audio are disclosed. At least two transforms are applied on an audio signal, each with different transform periods for better resolutions at both low and high frequencies. The transform coefficients are selected and combined such that the data rate remains similar as a single transform. The transform coefficients may be coded with a fast lattice vector quantizer. The quantizer has a high rate quantizer and a low rate quantizer. The high rate quantizer includes a scheme to truncate the lattice. The low rate quantizer includes a table based searching method. The low rate quantizer may also include a table based indexing scheme. The high rate quantizer may further include Huffman coding for the quantization indices of transform coefficients to improve the quantizing / coding efficiency.

Description

[0001] Cross References to Related Applications [0002] This application is related to co-pending and commonly-owned US Patent Application Serial No. 11 / 580,682 (Attorney Attorney No. 199-0524US), entitled "Fast Lattice Vector Quantization," filed on the same date. The contents of said application are incorporated herein by reference. technical field [0003] The present invention relates to encoding and decoding audio signals, and more particularly to encoding and decoding audio signals having an audio bandwidth of up to about 22 kHz using at least two transforms. Background technique [0004] Audio signal processing is used in many systems that create or reproduce sound from sound signals. With the development of digital signal processors (DSP), many signal processing functions are performed digitally. To do this, an audio signal is created from sound waves, converted to digital data, processed for the desired effect, converted back to analog, and reproduced as sound wa...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G10L19/02G10L11/00H03M7/40G06F3/14H04N7/14
CPCG10L19/0212G10L19/022
Inventor 谢敏杰朱彼德
Owner HEWLETT PACKARD DEV CO LP
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