Audio Classification Based on Perceptual Quality for Low or Medium Bit Rates

摘要

The quality of encoded signals can be improved by reclassifying AUDIO signals carrying non-speech data as VOICE signals when periodicity parameters of the signal satisfy one or more criteria. In some embodiments, only low or medium bit rate signals are considered for re-classification. The periodicity parameters can include any characteristic or set of characteristics indicative of periodicity. For example, the periodicity parameter may include pitch differences between subframes in the audio signal, a normalized pitch correlation for one or more subframes, an average normalized pitch correlation for the audio signal, or combinations thereof. Audio signals which are re-classified as VOICED signals may be encoded in the time-domain, while audio signals that remain classified as AUDIO signals may be encoded in the frequency-domain.

主权项

1. A method for encoding signals, the method, which is performed by an audio coder, comprising:
receiving a digital signal comprising audio data; classifying the digital signal as an AUDIO signal; re-classifying the digital signal as a VOICED signal when classifying conditions are satisfied, wherein, the classifying conditions include: pitch differences between sub-frames in the digital signal are less than a first threshold, an average normalized pitch correlation value for the sub-frames in the digital signal is greater than a second threshold, and a smoothed pitch correlation obtained according to the average normalized pitch correlation value is greater than a third threshold; wherein each of the pitch differences is an absolute value of the difference between two pitch values corresponding to two sub-frames respectively; and encoding the re-classified VOICED signal in the time-domain when one or more encoding conditions are satisfied, wherein the one or more encoding conditions include: a coding rate of the digital signal is below a fourth threshold.