Loudness equalization system

1. A method for loudness equalization, comprising:

receiving input loudness data at an audio processing system;

converting gain data of the input loudness data to a linear scale at the audio processing system;

determining a reciprocal of a gain-linear loudness value as a function of the converted gain data using the audio processing system;

determining a compression ratio using the audio processing system;

performing temporal smoothing and look ahead processing using the audio processing system; and

outputting gain data as a function of the temporal smoothing and look ahead processing using the audio processing system.

2. The method of claim 1 wherein converting the gain data of the input loudness data to the linear scale comprises raising the gain data to a power.

3. The method of claim 1 wherein determining a compression ratio comprises raising to a power.

4. The method of claim 3 wherein the power is greater than 0 and less than or equal to 1.

5. The method of claim 1 further comprising receiving an input audio signal at the audio processing system and outputting a gain-adjusted audio signal using the gain data.

6. The method of claim 5 further comprising performing segmentation processing of the input audio signal.

7. The method of claim 5 further comprising performing classification processing of the input audio signal.

8. The method of claim 5 further comprising selecting am algorithm for processing the input audio signal.

9. The method of claim 5 further comprising performing constant gain or compression processing of the input audio signal.

10. A method for processing audio data, comprising:

receiving an encoded audio data signal having a first bit rate;

generating a plurality of sub-bands of the encoded audio data signal;

performing adaptive pulse code modulation (APCM) processing of predetermined low frequency sub-bands of the encoded audio data signal at the first bit rate using a step size that is separately determined for each of the low frequency sub-bands; and

performing APCM processing of predetermined high frequency sub-bands of the encoded audio data signal at a second bit rate that is lower than the first bit rate using a step size that is separately determined for each of the high frequency sub-bands; and

generating an output audio signal using the APCM processed low frequency sub-bands of the encoded audio data signal and the APCM processed high frequency sub-bands of the encoded audio data signal.

11. The method of claim 10 wherein selection of the predetermined low-frequency bands is performed as a function of a sampling rate of the encoded audio signal.

12. The method of claim 10 wherein the step size is modified using a perceptual step size adjustment circuit.

13. The method of claim 10 wherein the step size is multiplied to allow for a partial-bit transmission rate.

14. The method of claim 13 wherein the partial-bit transmission rate is used to generate a preliminary step size for a next input signal quantization.

15. The method of claim 10 wherein encoded data outputs from a data encoder are provided to a bitstream assembler to generate an encoded bitstream.

16. The method of claim 10 wherein the predetermined high frequency bands are above a 0.5 equivalent rectangular bandwidth in width.

17. The method of claim 10 wherein the predetermined high frequency bands are between a 0.5 and 1.0 equivalent rectangular bandwidth in width.

18. The method of claim 10 wherein frequency bands between a 0.5 and 1.0 equivalent rectangular bandwidth in width are quantized at a lower bit rate.

19. The method of claim 10 wherein frequency bands between a 0.5 and 1.0 equivalent rectangular bandwidth in width are quantized at a bit rate of 6 bits or less.

20. The method of claim 10 wherein the high frequency bands are quantized at a lower bit rate to provide a resolution within one equivalent rectangular bandwidth.