US 5,210,796 AGranted

Stereo/monaural detection apparatus

AssigneeSony Corporation

InventorsAtsushi Hirabayashi, Kenji Komori, Kyoichi Murakami

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Abstract

A stereo/monaural detection apparatus for detecting whether two-channel input audio signals are stereo or monaural, wherein the level difference between the input audio signals is calculated, and after the signal representing the level difference is discriminated with a predetermined hysteresis maintained, a stereo/monaural detection is performed in accordance with the result of such discrimination, thereby preventing an erroneous detection that may otherwise be caused by any level difference variation during a short time as in a case where the sound field is positioned at the center in the stereo signals. And the discrimination with the hysteresis is partially inhibited in response to the signal obtained by discriminating the level sum of the input audio signals at a predetermined reference level, hence preventing instability of the operation when the audio input level is extremely feeble.

Claims11

Dependent claims

A stereo/monoaural detection apparatus comprising:

two-channel input terminals respectively supplied with two-channel audio signals;
a substracting circuit for subtracting one of said two-channel audio signals from the other and producing a difference signal;
and
hysteresis discriminating means supplied with the difference signal from said subtracting circuit for performing level discrimination on the difference signal and detecting when a level of the difference signal is above a first threshold level and detecting when a level of the difference signal is below a second, lower threshold level and including a hysteresis circuit for performing said level detecting with a hysteresis effect so that every crossing by the difference signal of the first and second thresholds does not produce a corresponding change in an output signal of said hysteresis discriminating means, said output signal having a first level when two-channel audio signals are stereo signals and a second level when said two-channel audio signals are monaural signals.

1 more element

Dependencies are inferred from the claim text.