Audio amplifier clipping avoidance method and apparatus

A method of processing an audio signal to avoid amplifier clipping, comprising the steps of:

• generating a zero crossing signal identifying half cycles for the audio signal;
• delaying the zero crossing signal for a particular time period;
• determining a scaling factor for a particular half cycle of the audio signal based on an amplifier clip avoidance threshold, and peak amplitude of the audio signal within the particular half cycle;
• and
• modifying the particular half cycle of the audio signal with the scaling factor using the delayed zero crossing signal when the audio signal has an amplitude peak greater than the amplifier clip avoidance threshold during the particular half cycle.

An apparatus for processing an audio signal to avoid amplifier clipping, comprising the steps of:

• means for generating a transition signal indicating signal segments based on transition points of the audio signal across a particular signal level;
• means for delaying the audio signal for a particular delay period to produce a delayed audio signal;
• means for delaying the transition signal for the particular delay period to produce a delayed transition signal;
• means for generating a scaling factor for each signal segment based on an amplifier clip avoidance threshold signal level, and peak amplitude of the audio signal during each signal segment;
• means for storing each scaling factor during the particular delay period;
• and
• means for applying scaling factors from the means for storing to corresponding signal segments of the delayed audio signal in response to the delayed transition signal.

The apparatus for processing an audio signal, comprising:

• a zero crossing detector coupled to the audio signal and having an output of a transition signal identifying segments of the audio signal;
• a scaling factor generator coupled to the audio signal and generating a scaling factor for the identified segments of the audio signal based on an amplifier clip avoidance threshold, and peak amplitude of the audio signal within each identified segment;
• a scaling module coupled to the audio signal and to the scaling factor generator, the scaling module combining the identified segments of the audio signal with corresponding scaling factors to produce a modified audio signal having no amplitude peaks greater than the amplifier clip avoidance threshold;
• a first delay module coupled to the audio signal and having an output of a delayed audio signal with a delay of a particular delay period;
• a second delay module coupled to the transition signal and providing a delayed transition signal with a delay of the particular delay period;
• and
• a memory module coupled to the scaling factor generator, the memory module being responsive to the transition signal to store each scaling factor;
• wherein the memory module outputs a stored scaling factor in response to the delayed transition signal, and the scaling module applies the stored scaling factor to the delayed audio signal to produce the modified audio signal.

An apparatus for processing an audio signal, comprising:

• a first delay module coupled to the audio signal and having an output of a delayed audio signal with a delay of a particular delay period;
• a zero crossing detector coupled to the audio signal and having an output of a transition signal indicating signal segments of the audio signal;
• a second delay module coupled to the transition signal and providing a delayed transition signal with a delay of the particular delay period;
• a scaling factor generator coupled to the audio signal and to the transition signal, the scaling factor generator outputting a scaling factor for each signal segment based on an amplifier clip avoidance threshold, and peak amplitude of the audio signal within each signal segment;
• a memory module coupled to the scaling factor generator, the memory module being responsive to the transition signal to store each scaling factor, and being responsive to the delayed transition signal to output a stored scaling factor;
• and
• a scaling module responsive to the delayed audio signal and to the stored scaling factor to produce a modified audio signal having no signal segments with an amplitude peak greater than the amplifier clip avoidance threshold.