Design of the coupling schemes for the AC-3 coder in stereo coding

When applying the Dolby AC-3 coder for stereo music compression, the coupling scheme that combines the two channels of stereo audio signals at high frequency into one channel is the key technology for Dolby AC-3 to achieve the bit rates lower than 96/spl times/2 kbits/sec while preserving high stereo audio quality. This paper proposes four coupling methods for the AC-3 encoder. These four methods vary with the complexity and performance. These four methods are compared through both subjective and objective tests. These four coupling methods are also combined with the dithering scheme and examined through subjective and objective tests. The result shows that the dithering scheme can effectively ease the coupling artifacts and enhance the audio quality.