Method and apparatus for maintaining speech audibility in multi-channel audio with minimal impact on surround experience

An apparatus including a circuit for improving audibility of speech in a multi-channel audio signal, comprising:

• a circuit that is configured to receive the multi-channel audio signal, wherein the multi-channel audio signal includes a left channel, a right channel, a left surround channel, a right surround channel, and a center channel, wherein the center channel contains speech audio, and wherein the left channel, the right channel, the left surround channel, and the right surround channel contain non-speech audio;
• a first comparison circuit that is configured to compare a power spectrum of the left channel and a power spectrum of the center channel to generate a left attenuation factor, and to compare a power spectrum of the right channel and the power spectrum of the center channel to generate a right attenuation factor, wherein the power spectrum of the left channel is generated by a first N-band power estimator as a first multiband power spectrum having N bands, and wherein the power spectrum of the right channel is generated by a second N-band power estimator as a second multiband power spectrum having N bands, where N is greater than one;
• a second comparison circuit that is configured to compare a power level of the left surround channel and a power level of the center channel to generate a left surround attenuation factor, and to compare a power level of the right surround channel and the power level of the center channel to generate a right surround attenuation factor, wherein the power level of the left surround channel is generated over the left surround channel considered as a single band, and wherein the power level of the right surround channel is generated over the right surround channel considered as a single band;
• a first multiplier that is configured to adjust the left attenuation factor according to a speech likelihood value to generate an adjusted left attenuation factor;
• a second multiplier that is configured to adjust the right attenuation factor according to the speech likelihood value to generate an adjusted right attenuation factor;
• a third multiplier that is configured to adjust the left surround attenuation factor according to the speech likelihood value to generate an adjusted left surround attenuation factor;
• a fourth multiplier that is configured to adjust the right surround attenuation factor according to the speech likelihood value to generate an adjusted right surround attenuation factor;
• a first amplifier that is configured to attenuate the left channel using the adjusted left attenuation factor;
• a second amplifier that is configured to attenuate the right channel using the adjusted right attenuation factor;
• a third amplifier that is configured to attenuate the left surround channel using the adjusted left surround attenuation factor;
• and
• a fourth amplifier that is configured to attenuate the right surround channel using the adjusted right surround attenuation factor.

A computer program embodied in tangible non-transitory recording medium for improving audibility of speech in a multi-channel audio signal, the computer program controlling a device to execute processing comprising:

• receiving the multi-channel audio signal, wherein the multi-channel audio signal includes a left channel, a right channel, a left surround channel, a right surround channel, and a center channel, wherein the center channel contains speech audio, and wherein the left channel, the right channel, the left surround channel, and the right surround channel contain non-speech audio;
• comparing a power spectrum of the left channel and a power spectrum of the center channel to generate a left attenuation factor, wherein the power spectrum of the left channel is generated by a first N-band power estimator as a first multiband power spectrum having N bands, wherein N is greater than one;
• comparing a power spectrum of the right channel and the power spectrum of the center channel to generate a right attenuation factor, wherein the power spectrum of the right channel is generated by a second N-band power estimator as a second multiband power spectrum having N bands;
• comparing a power level of the left surround channel and a power level of the center channel to generate a left surround attenuation factor, wherein the power level of the left surround channel is generated over the left surround channel considered as a single band;
• comparing a power level of the right surround channel and the power level of the center channel to generate a right surround attenuation factor, wherein the power level of the right surround channel is generated over the right surround channel considered as a single band;
• adjusting the left attenuation factor, the right attenuation factor, the left surround attenuation factor, and the right surround attenuation factor according to a speech likelihood value to generate an adjusted left attenuation factor, an adjusted right attenuation factor, an adjusted left surround attenuation factor, and an adjusted right surround attenuation factor;
• and
• attenuating the left channel using the adjusted left attenuation factor, the right channel using the adjusted right attenuation factor, the left surround channel using the adjusted left surround attenuation factor, and the right surround channel using the adjusted right surround attenuation factor.

An apparatus for improving audibility of speech in a multi-channel audio signal, comprising:

• means for receiving the multi-channel audio signal, wherein the multi-channel audio signal includes a left channel, a right channel, a left surround channel, a right surround channel, and a center channel, wherein the center channel contains speech audio, and wherein the left channel, the right channel, the left surround channel, and the right surround channel contain non-speech audio;
• first means for comparing a power spectrum of the left channel and a power spectrum of the center channel to generate a left attenuation factor, and for comparing a power spectrum of the right channel and the power spectrum of the center channel to generate a right attenuation factor, wherein the power spectrum of the left channel is generated by a first N-band power estimator as a first multiband power spectrum having N bands, and wherein the power spectrum of the right channel is generated by a second N-band power estimator as a second multiband power spectrum having N bands, where N is greater than one;
• second means for comparing a power level of the left surround channel and a power level of the center channel to generate a left surround attenuation factor, and for comparing a power level of the right surround channel and the power level of the center channel to generate a right surround attenuation factor, wherein the power level of the left surround channel is generated over the left surround channel considered as a single band, and wherein the power level of the right surround channel is generated over the right surround channel considered as a single band;
• means for adjusting the left attenuation factor, the right attenuation factor, the left surround attenuation factor, and the right surround attenuation factor according to a speech likelihood value to generate an adjusted left attenuation factor, an adjusted right attenuation factor, an adjusted left surround attenuation factor, and an adjusted right surround attenuation factor;
• and
• means for attenuating the left channel using the adjusted left attenuation factor, for attenuating the right channel using the adjusted right attenuation factor, for attenuating the left surround channel using the adjusted left surround attenuation factor, and for attenuating the right surround channel using the adjusted right surround attenuation factor.