Embedded Audio Coder (EAC)
Figure 1. EAC - a high performance scalable audio coder.
An embedded audio coder (EAC) has been developed that pushes the state-of-the-art of the scalable audio compression. The compression performance of EAC rivals that of the best avail-able non-scalable commercial audio coders, e.g., Real and Windows Media Audio (WMA), and outperforms audio compression standard such as MP3 and MPEG-4. Yet, the EAC compressed bitsteram is fully scalable in terms of compression ratio (coding bitrate), number of audio channels and audio sampling rate. The key technology that enables the efficient embedded audio coding is the implicit auditory masking. By deriving the auditory JND threshold from coded coefficients, and reordering the coding of the coefficients according to the threshold, EAC eliminates a substantial fixed overhead in the audio compress, and thus greatly improve the audio compression performance. As a highly efficient embedded audio coder, EAC has widespread applications in audio storage and streaming.
The EAC codec is well implemented. It can encode a stereo audio in about 8x real time, decode in 20x real time, and parse the audio (scalably adjust the bitrate, # of channels and output sampling rate) in 1000x real time (on a Pentinum III 800Mhz CPU). The speed of the EAC scaling operation is at least two magnitude faster than any existing audio encoders. As a highly efficient embedded audio coder, EAC has widespread applications in audio storage and streaming.
For more information of the EAC coder, please refer to the following:
We later extend EAC to PLEAC, which stands for the progressive-to-lossless embedded audio codec. Through the use of a low noise reversible MDCT module, PLEAC compresses the audio to lossless. Then low quality, bitrate, sampling rate compressed audio can be extracted from the master lossless compressed PLEAC audio stream.
©Copyright by Jin Li, Nov. 23, 2004