Method and system for compressing the dynamic range of audio signals
AssigneeBritish Broadcasting Corporation
InventorStephen G. T. Wilson
Life of this patent
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Abstract
An audio signal has its dynamic range compressed by a system which first samples a block of the audio signal (10), typically several seconds long. The level of the signal in this block is analyzed (12, 14) and an ideal signal level is calculated for the block (16, 18, 20). A gain control signal is then derived which adjusts the gain applied to that block towards that required to give the calculated ideal signal level.
Claims33
A method for compressing the dynamic range of an audio signal comprising the steps of sampling a block of the audio signal, deriving an ideal signal level for that block of audio signal, deriving a gain control signal for adjusting the gain applied to that block towards the said ideal signal level, and deriving a further gain control signal to reduce the gain applied to the block when a portion of the block exceeds a predetermined amplitude limit.
A system for compressing the dynamic range of an audio signal comprising means for sampling a block of the audio signal means for receiving the block of the audio signal and deriving an ideal signal level for that block of the audio signal, means responsive to the ideal signal level for that block for deriving a gain control signal for adjusting the gain applied to that block towards the ideal signal level, means for detecting when the amplitude of the block of the audio signal exceeds a predetermined limit, and means for adjusting the gain control signal such that the gain applied to that block of the audio signal reduces its amplitude to less than the predetermined limit.
A method for compressing the dynamic range of an audio signal comprising the steps of sampling a block of the audio signal, deriving an ideal signal level for that block of audio signal, deriving a gain control signal for adjusting the gain applied to that block towards the said ideal signal level, wherein the gain control signal is derived such that the said ideal signal level will not be reached until at least the end of that block of the audio signal.
A method for compressing the dynamic range of an audio signal comprising the steps of sampling a block of the audio signal, deriving an ideal signal level for that block of audio signal, deriving a gain control signal for adjusting the gain applied to that block towards the said ideal signal level, wherein the gain control signal is derived such that the said ideal signal level will be reached substantially by the end of that block of the audio signal.
A method for compressing the dynamic range of an audio signal comprising the steps of sampling a block of the audio signal, deriving an ideal signal level for that block of audio signal, deriving a gain control signal for adjusting the gain applied to that block towards the said ideal signal level, wherein the gain control signal is derived so as to adjust the gain at a maximum rate of 72 dB per minute.
A method for compressing the dynamic range of an audio signal comprising the steps of sampling a block of the audio signal, deriving an ideal signal level for that block of audio signal, deriving a gain control signal for adjusting the gain applied to that block towards the said ideal signal level, wherein the gain control signal is derived so as to hold the audio signal level substantially constant during transient increases and decreases in amplitude in that block of the audio signal.
A system for compressing the dynamic range of an audio signal comprising means for sampling a block of the audio signal, means for receiving the block of the audio signal and deriving an ideal signal level for that block of the audio signal, means responsive to the ideal signal level for that block for deriving a gain control signal for adjusting the gain applied to that block towards the ideal signal level, wherein the gain control signal deriving means operates such that the ideal signal level will not be reached until at least the end of that block of the audio signal.
A system for compressing the dynamic range of an audio signal comprising means for sampling a block of the audio signal, means for receiving the block of the audio signal and deriving an ideal signal level for that block of the audio signal, and means responsive to the ideal signal level for that block for deriving a gain control signal for adjusting the gain applied to that block towards the ideal signal level, wherein the gain control signal deriving means operates such that the ideal signal level will be reached substantially by the end of that block of the audio signal.
A system for compressing the dynamic range of an audio signal comprising means for sampling a block of the audio signal, means for receiving the block of the audio signal and deriving an ideal signal level for that block of the audio signal, means responsive to the ideal signal level for that block for deriving a gain control signal for adjusting the gain applied to that block towards the ideal signal level, wherein the gain control signal deriving means operates to produce a gain control signal which will adjust the gain substantially at 72 dB per minute.
A system for compressing the dynamic range of an audio signal comprising means for sampling a block of the audio signal, means for receiving the block of the audio signal and deriving an ideal signal level for that block of the audio signal, means responsive to the ideal signal level for that block for deriving a gain control signal for adjusting the gain applied to that block towards the ideal signal level, wherein the gain control signal deriving means operates to produce a gain control signal which will hold the signal level substantially constant during transient increases and decreases in amplitude in that block of the audio signal.
Dependencies are inferred from the claim text.