Audio coding at low bitrates suffers from artifacts due to spectrum

truncation.

Typical audio codecs code multi-channel sources using transforms across

the channels to remove redundancy such as middle (mid)

- side (M/S) coding.

At low bitrates, the spectrum of the coded channels is truncated and

the spectrum of the channels with lower energy, such as

the side channel, is truncated severely, sometimes entirely.

This results in a muffled sound due to truncation of all coded

channels beyond a certain frequency.

It also results in a loss of spatial image even at low frequencies

due to severe truncation of the side channel.

Previously we have developed a low bitrate coding method to combat

the loss of higher frequencies caused by spectrum truncation.

In this paper, we present a novel low bitrate audio coding scheme to

mitigate the loss of spatial image.

Listening tests show that the combination of the two low bitrate coding

methods results in a audio codec that can get good quality even

at bitrates as low as 32kbps for stereo content with low decoder

complexity.

PDF file

In  Proc. Int'l Conf. Acoustics, Speech, and Signal Processing

Publisher  IEEE
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