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Low-Power MPEG-4 HE-AAC Version-2 Encoder

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In MPEG-4 HE-AAC version-2 encoder, the analysis/synthesis complex-exponential modulation filter banks are used in spectral band replication (SBR) and parametric stereo (PS) coding. Due to the aliasing interference, the complex banks instead of real banks are adopted in the SBR and PS coding. However, the additional overhead from the complex values in the CEMFB and the subsequent processing have led to high operational overhead. Our previous work has designed the SBR encoders based on the real-domain cosine modulation filter banks; we proposed a complexification-based approach for the SBR coding. This paper extends the work into PS coding. An approximate method for parameters estimation is proposed to save operational overhead with only one CEMFBanalysis channel. Also, a phase-adjustment down-mixing method is proposed to reduce energy vanish effects.

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