This paper discusses a new DSP based real-time implementation of the MPEG-2/4 AAC standards using a set of non-optimal solutions to reduce the computational load. These solutions comprise a novel implementation of a MDCT-based psychoacoustic model, managing a birth/death scheme which aims to overcome false power spectrum estimates due to the cosine transform, a smoothing of the scalefactors guided by an estimation of the increment in the quantization noise and a loop-free bit allocation method based on an overestimation of the noise level. These techniques provide both robustness and efficiency to the scheme. Other fixed-point DSP programming considerations required to achieve the real-time implementation, including a choice of a MDCT fast algorithm, are presented.
Click to purchase paper as a non-member or login as an AES member. If your company or school subscribes to the E-Library then switch to the institutional version. If you are not an AES member and would like to subscribe to the E-Library then Join the AES!
This paper costs $33 for non-members and is free for AES members and E-Library subscribers.