System for adjusting loudness of audio signals in real time

A system for adjusting loudness of an audio signal, the system comprising:

• a loudness analysis module comprising one or more processors, the loudness analysis module configured to:
• access a frame of an audio signal, the frame comprising a plurality of samples of the audio signal,
• measure loudness values for windows of the samples in the frame to determine a plurality of loudness values,
• determine a plurality of weights for applying to at least some of the of loudness values, the weights determined based at least partly on a recency of the loudness values, such that when the weights are applied to at least some of the loudness values, a first set of weights is applied to loudness values for a first window of samples that is separated from a current window of samples by no more than a time duration in order to emphasize loudness contributions due to the samples in the first window and a second set of weights different from the first set of weights is applied to loudness values for a second window of samples that is separated from the current window of samples by more than a time duration in order to deemphasize loudness contributions due to the samples in second window,
• apply the plurality of weights to the at least some of the loudness values, and
• compute a weighted average of the at least some of the plurality of loudness values in the frame to produce an adjusted loudness value for the first frame;
• a dynamics control module configured to adjust loudness of the audio signal based at least partly on the adjusted loudness value;
• and
• an output module configured to provide the adjusted audio signal for playback.

A method of adjusting loudness of an audio signal, the method comprising:

• sampling an audio signal to produce blocks of samples;
• measuring initial loudness values for the blocks of samples in the audio signal to produce a plurality of initial loudness values;
• computing gain values to be applied to the audio signal based at least partly on the initial loudness values;
• determining a plurality of weights for applying to at least some of the plurality of initial loudness values or to at least some of the gain values;
• applying the plurality of weights to the at least some of the initial loudness values or to the at least some of the gain values, such that first set of weights is applied to emphasize loudness contributions due to samples in one or more blocks that are separated from a current block by no more than a time duration and a second set of weights different from the first set of weights is applied to deemphasize loudness contributions due to samples in one or more second blocks that are separated from the current block by more than the time duration;
• computing a weighted average of the at least some of the initial loudness values or of the at least some of the gain values;
• adjusting loudness of the audio signal based at least partly on the computed gain values and the weighted average;
• and
• providing the adjusted audio signal for playback.