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Reducing scale factor transmission cost for MPEG-2 AAC using a lattice

A technology of scale factor and audio encoder, which is applied in speech analysis, instruments, etc., can solve the problems of scale factor performance and high bit cost of lowering masking level technology

Inactive Publication Date: 2006-02-15
DOLBY LAB LICENSING CORP
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Problems solved by technology

Because the scale factor is differentially encoded and then Huffman encoded (a larger difference means a longer Huffman codeword), a high variance in the scale factor means that the bit cost of transmitting the scale factor is very high, which reduces the Performance of Scale Factor Estimation for Masking Level Techniques

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  • Reducing scale factor transmission cost for MPEG-2 AAC using a lattice
  • Reducing scale factor transmission cost for MPEG-2 AAC using a lattice
  • Reducing scale factor transmission cost for MPEG-2 AAC using a lattice

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Embodiment Construction

[0022] figure 1 A simple, high-level schematic diagram of the AAC encoding process incorporating dynamic programming scalefactor optimization according to the present invention is shown. The figure shows scalefactor optimization according to the invention combined with direct scalefactor estimation from the above model information. While other scaling factor derivation techniques can be improved using the techniques of the present invention, the present invention is particularly well suited to use of this direct estimation technique.

[0023] existfigure 1 In , the input audio is transformed using MDCT2, followed by preprocessing4 (eg: temporal noise shaping (TNS), prediction and mid-side coding (MS) in stereo applications). This input can also be passed to the psychoacoustic model 6, which calculates the masking level. As mentioned above, the masking model is used directly to calculate the scale factor for each frequency band ("Scale Factor Computation" 8). Although the in...

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Abstract

A perceptual encoder divides an audio signal into successive time blocks, each time block is divided into frequency bands, and a scale factor is assigned to each of ones of the frequency bands. Bits per block increase with scale factor values and band-to-band variations in scale factor values. A preliminary scale factor for each of ones of the frequency bands is determined, and the scale factors for the each of ones of the frequency bands is optimized, the optimizing including increasing the scale factor to a value greater than the preliminary scale factor value for one or more of the frequency bands such that the increase in bit cost of the increasing is the same or less than the reduction in bit cost resulting from the decrease in band-to-band variations in scale factor values resulting from increasing the scale factor for one or more of the frequency bands.

Description

Background technique [0001] Typical transform and filter bank audio coding techniques such as layers 1 to 3 of MPEG-1, Dolby AC3 (also known as Dolby Digital) (Dolby, Dolby Digital and Dolby AC-3 are trademarks of Dolby Laboratories Licensing Corporation) and MPEG-2 Advanced Audio Coding (AAC) reduces transmission data rates by dynamically allocating bits in the time and frequency domains to remove inaudible redundancies in audio signals. The dynamic allocation of the bits is typically based on psychoacoustic principles related to the signal. Further details of Dolby AC3 can be found in the Digital Audio Compression (AC-3) Standard Ratified 10 November 1994, (Rev 1) Annex A Added 12 April 1995, (Rev 2) 24 May 1995 Added 13 errata and (Rev 3) Added Appendices B and C on 20 December 1995. Further details of AAC can be found in "ISO / IEC MPEG-2 Audio Coding by Bosi et al, presented at the 101st Convention 1996 November 8-11, Los Angeles, Audio Engineering Society Preprint 4382)....

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G10L19/02
CPCG10L19/035
Inventor 马克·S.·温登
Owner DOLBY LAB LICENSING CORP
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