Controlling a noise-shaping feedback loop in a digital audio signal encoder avoiding instability risk of the feedback

摘要

A method and apparatus are provided for controlling the shaping of encoding noise during the ADPCM encoding of a digital audio input signal. The noise-shaping is carried out through the use of feedback that comprises filtering noise. The method includes the following steps: obtaining a parameter for indicating a high spectral dynamic range of the signal, the parameter indicating a risk of instability of the feedback; detecting a risk of instability by comparing the indication parameter to at least one predetermined threshold; limiting the feedback in the event that a risk of instability is detected; and gradually reactivating the feedback over a predetermined number of frames subsequent to the current frame for which the feedback is limited. Also provided is an encoder with feedback, including a control module implementing the control method as described.

主权项

1. A method comprising:
receiving a digital audio input signal by a coder device; performing an ADPCM-type coding of the digital audio input signal by the coder device to produce multiplexed quantization indices; during the ADPCM-type coding of the digital audio input signal, controlling shaping of coding noise by implementing a feedback by the coder device comprising a filtering of the noise, wherein controlling shaping comprises the following acts: obtaining a second reflection coefficient arising from a linear prediction analysis of the input signal, this parameter indicating a large spectral dynamic range of the signal and a risk of instability of the feedback; detection of a risk of instability by comparing the second reflection coefficient with at least one predetermined threshold; deactivation of the feedback by the coder device in the case of detection of risk of instability; and progressive reactivation of the feedback by the coder device over several frames following a current frame for which the feedback has been deactivated; and transmitting the quantization indices on a transmission channel.