Electrical audio signal processing systems and devices – Binaural and stereophonic – Pseudo stereophonic
Reexamination Certificate
1999-02-09
2001-09-18
Harvey, Minsun Oh (Department: 2644)
Electrical audio signal processing systems and devices
Binaural and stereophonic
Pseudo stereophonic
C381S001000, C381S017000
Reexamination Certificate
active
06292570
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
The invention relates to a sound reproduction system comprising a left channel and a right channel loudspeaker, a surround decoder unit for decoding at least one input signal into at least one rear surround signal and two channel stereophonic signals, a surround signal processing unit for converting the rear surround signal(s) into a first and a second surround signal and for localizing these surround signals at virtual sound sources located away from the left channel and the right channel loudspeakers, and first combining means coupled to one of the loudspeakers for combining the first surround signal with one of the stereophonic signals, and second combining means coupled to the other loudspeaker for combining the second surround signal with the other stereophonic signal, and the surround signal processing unit further comprises filter means.
The invention further relates to a surround signal processing unit.
The invention further relates to a sound/visual reproduction system comprising a sound reproduction system.
The invention further relates to a method for processing an input surround sound signal.
2. Description of The Related Art
To improve listener perceived characteristics, multi-channel sound reproduction systems are known which include a surround-sound channel (often referred to in the past as an “ambience” or “special-effects” channel) in addition to left and right (and optimally, center) sound channels. These systems are now relatively common in motion picture theatres and are becoming more and more common in the homes of the customers. A driving force behind the proliferation of such systems in consumers' homes is the widespread availability of surround-sound home video software, mainly surround-sound motion pictures (movies) made for theatrical release and subsequently transferred to home video media (e.g., videocassettes, videodisks, and broadcast or cable television).
Although home video media have two-channel stereophonic soundtracks, those two channels carry, by means of amplitude and phase matrix encoding, four channels of sound information, i.e., left, center, right and surround sound, usually identical to the two-channel stereophonic motion-pictures soundtracks from which the home video soundtracks are derived. As is also done in the motion picture theatre, the left, center, right, and surround channels are decoded and recovered by consumers with a matrix decoder, usually referred to as a “surround-sound” decoder. In the home environment, the decoder is usually incorporated in, or is an accessory to a videocassette player, videodisk player, or television set/video monitor.
In the case where stereophonic sound is reproduced in such a way as to provide a sound field expanding behind a listener or to localize a sound image behind a listener, two (front) loudspeakers are arranged in front of a listener for stereophonic sound reproduction and at least one or two rear loudspeakers are additionally arranged behind the listener for surround reproduction.
In the ordinary homes, however, since it is difficult to arrange the two rear loudspeakers and the center loudspeaker from the standpoint of space and cost, in practice, only L- and R-channel loudspeakers are installed on the front left and right sides of a listener. In this loudspeaker arrangement, it has become impossible to obtain sufficient surround sound effect. In the case of the sound reproduction system using a monophonic surround signal in particular, although this system has such a feature that a sound field can be obtained on the rear side of a listener or the sound image can be shifted, it has been impossible to obtain such effects as described above without arranging the rear loudspeakers.
To solve the above problem, it is known from the European Patent Application EP-A-0637191, corresponding to U.S. Pat. Nos. 5,579,396 and 5,761,315, to use a surround signal processing unit (apparatus) whereby a stereophonic sound effect, similar to the case where the rear loudspeakers are arranged, can be obtained on the basis of the sound reproduction through only the front left and right loudspeakers.
The inputted rear surround signal is processed by filter means and the processed signal is added to one of the stereophonic signals and then outputted to one of the pair of the loudspeakers. Further an inversion signal of the filter processed signal is added to the other of the stereophonic signals and then outputted to the other of the loudspeakers.
A disadvantage of this known sound reproduction system is that the perceived sound depends strongly on the position (of the head of the listener and) of the listener. Further, the filter characteristics are complex and dependent on the listener, for example, of the rear canal, head/torso, and/or pinna, resulting in possible failures of the requested results. Further, this known sound reproduction system is complex.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a sound reproduction system that does not have the drawbacks of the sound reproduction system as described above and, further, to provide a robust sound reproduction system whereby the operation of the filter topology is very robust against coefficient quantization. Further, the listeners position will be less relevant for the performance of the sound reproduction system.
To this end, a first aspect of the invention provides a sound reproduction system as described above, characterized in that the filter means of the surround signal processing unit comprises dividing means for dividing at least one predetermined frequency range of the rear surround signal(s) into at least two adjacent frequency bands, supplying a first selection of frequency bands as the first surround signal to the first combining means and a second selection of frequency bands as the second surround signal to the second combining means, the first and second selections being substantially disjunct, a sum of the first and second selections covering the predetermined frequency range.
By splitting the frequency range of the rear surround sound in disjunct frequency bands and supplying a first selection to the left loudspeaker and a second selection to the right loudspeaker, the spectrum has been widened resulting in a perceived surround sound.
It is to be noted that when the input signal is, for example, a MPEG signal having a stereophonic surround sound signal, the surround signal processing unit only has to localize these stereophonic surround signal at virtual sound sources located away from the left channel and right channel loudspeakers and no decoding into a first (for example, left) and second (for example, right) surround signal is necessary.
A second aspect of the invention provides a sound/visual reproduction system comprising such a sound reproduction system.
The use of the sound reproduction system in a sound/visual reproduction system, such as a television receiver, computer monitor, etc., enhances the reproduced sound considerable, resulting in a greatly improved customer satisfaction.
A third aspect of the invention provides a surround signal processing unit as used in the above-described sound reproduction system.
Such a surround signal processing unit can be used not only by a sound reproduction system and a sound/visual reproduction system, such as a television set, but also, for example, in computer sound cards and/or computer (sound) games.
A fourth aspect of the invention provides a method for processing an input surround sound signal into a left and a right channel output signal, characterized in that the method comprises the steps of dividing a predetermined frequency range of the input surround sound signal into at least two adjacent frequency bands, supplying a first selection of frequency band(s) to form after expanding the left channel output signal, supplying a second selection of frequency band(s) to form after expanding the right channel output signal, the first and second selections being substantially disjunct, a sum of the fir
Goodman Edward W.
Harvey Minsun Oh
Mei Xu
U.S. Philips Corporation
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