Efficient digital audio automatic gain control

An automatic gain control (AGC) circuit, comprising:

• an input adapted to receive a signal;
• a compression circuit coupled to the input having a compression ratio, the compression ratio being applied to the signal exceeding a first predetermined threshold, the compression ratio being applied as a function of a predetermined signal peak level,
• wherein said circuit further comprises a gain applied to the signal, which gain is not uniformly distributed to the signal,
• wherein the gain comprises a canonical signed digit (CSD) multiplier;
• a look-up table storing discrete sound pressure level (SPL) values and a second table storing information indicative of gain values,
• wherein the second table stores CSD codes rather than actual gain values;
• and
• a table storing only a fraction of actual gain values,
• wherein remaining actual gain values are determined by a scale factor.

An automatic gain control (AGC) circuit, comprising:

• an input adapted to receive a signal;
• a compression circuit coupled to the input having a compression ratio, the compression ratio being applied to the signal exceeding a first predetermined threshold, the compression ratio being applied as a function of a predetermined signal peak level,
• wherein the compression circuit comprises a state machine having a first and second comparator and a first and second register, the first comparator comparing the input signal to the content of the first register and the second comparator comparing the input signal to the content of the second register,
• wherein the content of the first register is moved to the second register when the input signal exceeds the first predetermined threshold.

An automatic gain control (AGC) circuit, comprising:

• an input adapted to receive a signal;
• a compression circuit coupled to the input having a compression ratio, the compression ratio being applied to the signal exceeding a first predetermined threshold, the compression ratio being applied as a function of a predetermined signal peak level,
• wherein said circuit further comprises a gain applied to the signal, which gain is not uniformly distributed to the signal,
• wherein the gain comprises a canonical signed digit (CSD) multiplier;
• and
• a look-up table storing discrete sound pressure level (SPL) values and a second table storing information indicative of gain values,
• wherein the SPL values are uniformly distributed.

An automatic gain control (AGC) circuit, comprising:

• an input adapted to receive a signal;
• a compression circuit coupled to the input having a compression ratio, the compression ratio being applied to the signal exceeding a first predetermined threshold, the compression ratio being applied as a function of a predetermined signal peak level,
• wherein said circuit further comprises a gain applied to the signal, which gain is not uniformly distributed to the signal,
• wherein the gain comprises a canonical signed digit (CSD) multiplier;
• and
• a look-up table storing discrete sound pressure level (SPL) values and a second table storing information indicative of gain values,
• wherein the SPL values are not uniformly distributed.

An automatic gain control (AGC) circuit, comprising:

• an input adapted to receive a signal;
• a compression circuit coupled to the input having a compression ratio, the compression ratio being applied to the signal exceeding a first predetermined threshold, the compression ratio being applied as a function of a predetermined signal peak level,
• wherein said circuit further comprises a gain applied to the signal, which gain is not uniformly distributed to the signal,
• wherein the gain comprises a canonical signed digit (CSD) multiplier;
• a look-up table storing discrete sound pressure level (SPL) values and a second table storing information indicative of gain values,
• wherein the second table stores CSD codes rather than actual gain values;
• and
• a table storing only a fraction of actual gain values,
• wherein the gain values are divided into blocks of numbers, the blocks being scaled with respect to each other.