Stereo signal down-mixing method, encoding/decoding apparatus and encoding and decoding system

An encoding apparatus, comprising:

• a time-frequency converting module, configured to convert a first channel time-domain signal and second channel time-domain signal in a stereo signal into a first channel frequency-domain signal and second channel frequency-domain signal;
• a first acquiring module, configured to obtain a frequency-domain channel signal level difference and a frequency-domain channel signal phase difference that are between the first channel frequency-domain signal and second channel frequency-domain signal;
• a second acquiring module, configured to:
• for each frequency bin in each frequency band, using a function based on the frequency-domain channel signal level difference and frequency-domain channel signal phase difference to obtain a down-mixed signal phase that is located between a phase of the first channel frequency-domain signal and a phase of the second channel frequency-domain signal;
• a third acquiring module, configured to calculate down-mixed signal amplitude for each frequency bin of each frequency band;
• and
• a down-mixing module, configured to obtain a frequency-domain down-mixed signal according to the down-mixed signal phase and down-mixed signal amplitude.

An encoding and decoding system, comprising:

• an encoding apparatus, configured to:
• convert a first channel time-domain signal and a second channel time-domain signal in a stereo signal into a first channel frequency-domain signal and a second channel frequency-domain signal;
• obtain a frequency-domain channel signal level difference and a frequency-domain channel signal phase difference that are between the first channel frequency-domain signal and second channel frequency-domain signal;
• for each frequency bin in each frequency band, using a function based on the frequency-domain channel signal level difference and frequency-domain channel signal phase difference to obtain a down-mixed signal phase that is located between a phase of the first channel frequency-domain signal and a phase of the second channel frequency-domain signal;
• calculate down-mixed signal amplitude for each frequency bin of each frequency band;
• obtain a frequency-domain down-mixed signal according to the down-mixed signal phase and down-mixed signal amplitude;
• encode the frequency-domain down-mixed signal or convert the frequency-domain down-mixed signal into a time-domain down-mixed signal and encode the time-domain down-mixed signal to obtain a down-mixed monophonic signal;
• and
• perform quantization encoding on the frequency-domain channel signal level difference and frequency-domain channel signal phase difference of each frequency band, and send the down-mixed monophonic signal and a quantization code;
• and
• a decoding apparatus, configured to:
• obtain, according to a received down-mixed monophonic signal, the frequency-domain down-mixed signal that has been decoded;
• obtain, according to a received quantization code, the frequency-domain channel signal level difference of each frequency band and frequency-domain channel signal phase difference of each frequency band;
• obtain a first channel and second channel frequency-domain signal amplitude and phase according to the frequency-domain down-mixed signal, the function, the frequency-domain channel signal level difference, and the frequency-domain channel signal phase difference;
• synthesize the first channel frequency-domain signal and second channel frequency-domain signal according to the first channel and second channel frequency-domain signal amplitude and phase;
• and
• convert the first channel frequency-domain signal and second channel frequency-domain signal into the first channel time-domain signal and second channel time-domain signal.