An Apple patent (number 20120170758) has appeared at the U.S. Patent & Trademark Office for a multi-channel sound panner. It shows that the company is working on simplified ways of implementing surround sound — and may hint at a feature of the rumored “iTV.”
A method and apparatus for multi-channel panning is provided. The panner can support an arbitrary number of input channels and changes to configurations to the output sound space. For example, the panner seamlessly handles changes in the number of input channels. Also, the panner supports changes to the number and positions of speakers in the output space.
In one embodiment, the panner allows continuous control of attenuation and collapsing. In one embodiment, the panner keeps source channels on the periphery of the sound space when collapsing channels. In one embodiment, the panner allows control over the path by which sources collapse.
Here’s Apple’s background on the invention: “Sound panners are important tools in audio signal processing. Sound panners allow an operator to create an output signal from a source audio signal such that characteristics such as apparent origination and apparent amplitude of the sound are controlled. Some sound panners have a graphical user interface that depicts a sound space having a representation of one or more sound devices, such as audio speakers.
“As an example, the sound space may have five speakers placed in a configuration to represent a 5.1 surround sound environment. Typically, the sound space for 5.1 surround sound has three speakers to the front of the listener (front left (L) and front right (R), center (C)) and two surround speakers at the rear (surround left (LS) and surround right (RS)), and one LFE channel for low frequency effects (LFE). A source signal for 5.1 surround sound has five audio channels and one LFE channel, such that each source channel is mapped to one audio speaker.
“When surround sound was initially introduced, dialog was typically mapped to the center speaker, stereo music and sound effects were typically mapped to the left front speaker and the right front speaker, and ambient sounds were mapped to the surround (rear) speakers. Recently, however, all speakers are used to locate certain sounds via panning, which is particularly useful for sound sources such as explosions or moving vehicles. Thus, an audio engineer may wish to alter the mapping of the input channels to sound space speakers, which is where a sound panner is very helpful.
“Moreover, panning can be used to create the impression that a sound is originating from a position that does not correspond to any physical speaker in the sound space by proportionally distributing sound across two or more physical speakers. Another effect that can be achieved with panning is the apparent width of origination of a sound. For example, a gunshot can be made to sound as if it is originating from a point source, whereas the sound of a supermarket can be made to sound as if it is originating over the entire left side of the sound space.
“Conventional sound panners present a graphical user interface to help the operator to both manipulate the source audio signal and to visualize how the manipulated source audio signal will be mapped to the sound space. However, given the number of variables that affect the sound manipulation, and the interplay between the variables, it is difficult to visually convey information to the operator in a way that is most helpful to manipulate the sound to create the desired sound. For example, some of the variables that an operator can control are panning forward, backward, right, and/or left. Further, the source audio data may have many audio channels.
“Moreover, the number of speakers in the sound space may not match the number of channels of data in the source audio data. In order to handle this complexity, some sound panners only allow the operator process one channel of source audio at a time. However, processing one channel at a time can be laborious. Furthermore, this technique does not allow audio engineers to effectively coordinate multiple speakers. Therefore, improved techniques are desired for visually conveying information in a user interface of a sound panner.
“The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.”
Aaron Eppolito is the inventor.