Unequal error protection for S3AC coding based on expanding window fountain codes

This paper presents a coding scheme to improve the performance of three-dimensional (3D) audio. The scheme is designed by the idea of joint source channel coding (JSCC) and is implemented by Expanding Window Fountain (EWF) codes for the 3D audio bitstreams after source coding of spatial squeeze surround audio coding (S3AC). EWF is one of unequal error protection (UEP) LT codes and the proposed scheme is achieved by that method for the case of two levels. Different from other transmissions with equal error protection (EEP) for each part of bitstreams, when transmitting the two parts of the bitstreams with downmixed mono signals and spatial side information after S3AC coding, this approach provides more protection to the part of spatial side information and comparatively less protection to the downmixed mono signals, and results in the improvement of the performance of the reproduced 3D audio especially on the aspect of the spatial perception. Objective simulation experiment has shown the proposed UEP scheme achieves a better performance than the EEP scheme on the aspect of spatial perception, for the bits error rates (BER) of spatial parameters can decrease dramatically to a low value of about 10−4, but BERs of downmixed mono signals and the case of EEP just decrease slightly to about 10−3.