Upmixing systems and methods for extending stereo signals to multi-channel formats

A computer-readable medium carrying instructions that, when executed by at least one processor, cause a computing system to perform operations comprising:

• receiving a stereo signal containing a left input channel and a right input channel;
• transforming, based at least on a short-time Fast Fourier Transform (s-t FFT), windowed overlapping sections of the stereo signal containing the left input channel and the right input channel to generate a set of frequency bins for the left input channel and the right input channel;
• generating a two-dimensional positional distribution plotting frequency versus normalized magnitude for the transformed stereo signal to identify a position in a left-right plane of each frequency bin in the set of frequency bins;
• identifying multiple portions of the transformed stereo signal to be extracted, wherein each portion of the transformed stereo signal is identified based on a respective region of interest within the two-dimensional positional distribution plotting frequency versus normalized magnitude;
• applying a filtering function to each respective region of interest to extract the multiple identified portions of the transformed stereo signal, wherein the filtering function attenuates the transformed stereo signal outside of the respective region of interest;
• transforming each of the multiple identified portions of the transformed stereo signal into a time domain output signal to generate an upmixed multi-channel time domain audio signal, wherein the upmixed multi-channel time domain audio signal is used for playback in a multi-channel sound field via a plurality of output components;
• generating a visual representation comprising the positions of the frequency bins in the set of frequency bins and positions of each of the identified portions of the transformed stereo signal in the multi-channel sound field, wherein the visual representation is generated to facilitate analysis of relative positions of the frequency bins and the identified portions of the transformed stereo signal in the multi-channel sound field;
• providing the visual representation for display in a user interface;
• and
• modifying a characteristic of the multi-channel sound field in response to a user input via the user interface based on the relative positions of the frequency bins and the identified portions of the transformed stereo signal.