Volume control for audio signals

Abstract

A motion picture soundtrack reproduction system has a center front soundtrack channel and a plurality of other soundtrack channels. A volume control adjusts the gain of all the channels. The volume control has a range of settings from a minimum to a maximum, the gain of the center front channel having substantially a first relationship to the volume control settings and the gain of the other channels having substantially a second relationship to the volume control settings, the relationships being such that for a range of volume control settings less than a first setting the gain of the center front channel remains substantially constant while the gain of the other channels decreases as the setting decreases or decreases more gradually than the gain of the other channels as the setting decreases.

The invention claimed is: 
     
       1. A motion picture soundtrack reproduction system, the system having a center front soundtrack channel and a plurality of other soundtrack channels, comprising
 a controller having a volume control for adjusting the gain of all the channels, the volume control having a range of settings from a minimum to a maximum, the controller having a first output for controlling the gain of the center front channel and a second output for controlling the gain of the other channels in response to settings of the volume control, the gain of the center front channel having a first relationship to the volume control settings and the gain of the other channels having a second relationship to the volume control settings, the relationships being such that for a range of volume control settings less than a first setting the gain of the center front channel (1) remains substantially constant while the gain of the other channels decreases as the setting decreases, or (2) decreases snore gradually than the gain of the other channels as the setting decreases.   
     
     
       2. A motion picture soundtrack reproduction system, comprising
 a center front soundtrack channel and a plurality of other soundtrack channels, each of said channels having adjustable gain and one or more loudspeakers, and   a controller having a volume control for adjusting the gain of all the channels, the volume control having a range of settings from a minimum to a maximum, the controller having a first output for controlling the gain of the center front channel and a second output for controlling the gain of the other channels in response to settings of the volume control the gain of the center front channel having a first relationship to the volume control settings and the gain of the other channels having a second relationship to the volume control settings, the relationships being such that for a range of volume control settings less than a first setting the gain of the center front channel (1) remains substantially constant while the gain of the other channels decreases as the setting decreases or (2) decreases more gradually than the gain of the other channels as the setting decreases.   
     
     
       3. A system according to  claim 1  or  claim 2  wherein the range of volume control settings less than said first setting extends down to the minimum control setting. 
     
     
       4. A system according to  claim 1  or  claim 2  wherein the range of volume control settings less than said first setting extends down to a second setting above the minimum control setting. 
     
     
       5. A system according to  claim 3  wherein for settings less than said second setting the gains of all the channels decrease in substantially the same way as the setting decreases and for such volume control settings the gain of the center front channel is greater than the gain of the other channels. 
     
     
       6. A system according to  claim 5  wherein for settings less than said second setting the gain of the center front channel is greater than the gain of the other channels by a substantially constant amount in the logarithmic domain. 
     
     
       7. A system according to  claims 1  wherein for settings greater than said first setting the gains of all the channels increase as the setting increases and for each of such volume control settings the gain of the center front channel and the gain of the other channels are substantially the same. 
     
     
       8. A system according to  claims 1  wherein when the volume control is set to a standard setting, each of the channels has a respective gain that produces a respective standard acoustic level in response to a signal having a respective standard reference level in the channel. 
     
     
       9. A system according to  claim 8  wherein said first setting is about said standard setting. 
     
     
       10. A method for volume control of a digital signal stream, comprising:
 reducing a setting of a volume control that controls overall loudness of a plurality of channels of the digital stream, the setting ranging from a minimum to a maximum;   in response to the reducing, adjusting a gain of a first channel and a gain of a second channel of the plurality of channels of the digital stream, for a range of volume control settings above a first setting of the volume control the adjusting decreases a contribution of the first channel and the second channel to the overall loudness of the plurality of channels of the digital stream in a substantially same manner, at one or more specific settings of the volume control below the first setting of the volume control the adjusting increases a proportionate contribution of the first channel, in relation to the second channel, to the overall loudness of the plurality of channels of the digital stream;   feeding an audio signal of the first channel to a first output;   feeding an audio signal of the second channel to a second output.   
     
     
       11. The method of claim 10, wherein the reducing employs digital controls. 
     
     
       12. The method of claim 10, wherein the second output is at least one of a left output, right output, and surround output. 
     
     
       13. The method of claim 10, wherein the digital signal stream is in a Dolby Digital format. 
     
     
       14. The method of claim 10, wherein first output is a center channel output. 
     
     
       15. The method of claim 10, wherein the digital signal stream is a multitrack digital soundtrack. 
     
     
       16. An apparatus for volume control of a digital signal stream, comprising:
 a subsystem, implemented at least partially in hardware that reduces a setting of a volume control that controls overall loudness of a plurality of channels of the digital stream, the setting ranging from a minimum to a maximum;   a subsystem, implemented at least partially in hardware that, in response to the reducing, adjusts a gain of a first channel and a gain of a second channel of the plurality of channels of the digital stream, for a range of volume control settings above a first setting of the volume control the gain adjust decreases a contribution of the first channel and the second channel to the overall loudness of the plurality of channels of the digital stream in a substantially same manner, at one or more specific settings of the volume control below the first setting of the volume control the gain adjust increases a proportionate contribution of the first channel, in relation to the second channel, to the overall loudness of the plurality of channels of the digital stream;   a subsystem, implemented at least partially in hardware that feeds an audio signal of the first channel to a first output;   a subsystem, implemented at least partially in hardware that feeds an audio signal of the second channel to a second output.   
     
     
       17. The apparatus of claim 16, wherein the reducing subsystem employs digital controls. 
     
     
       18. The apparatus of claim 16, wherein the second output is at least one of a left output, right output, and surround output. 
     
     
       19. The apparatus of claim 16, wherein the digital signal stream is in a Dolby Digital format. 
     
     
       20. The apparatus of claim 16, wherein first output is a center channel output. 
     
     
       21. The apparatus of claim 16, wherein the digital signal stream is a multitrack digital soundtrack. 
     
     
       22. A non-transitory computer readable medium, storing software instructions for volume control of a digital signal stream, which when executed by one or more processors cause performance of the steps of:
 reducing a setting of a volume control that controls overall loudness of a plurality of channels of the digital stream, the setting ranging from a minimum to a maximum;   in response to the reducing, adjusting a gain of a first channel and a gain of a second channel of the plurality of channels of the digital stream, for a range of volume control settings above a first setting of the volume control the adjusting decreases a contribution of the first channel and the second channel to the overall loudness of the plurality of channels of the digital stream in a substantially same manner, at one or more specific settings of the volume control below the first setting of the volume control the adjusting increases a proportionate contribution of the first channel, in relation to the second channel, to the overall loudness of the plurality of channels of the digital stream;   feeding an audio signal of the first channel to a first output;   feeding an audio signal of the second channel to a second output.   
     
     
       23. The non-transitory computer readable medium of claim 22, wherein the reducing employs digital controls. 
     
     
       24. The non-transitory computer readable medium of claim 22, wherein the second output is at least one of a left output, right output, and surround output. 
     
     
       25. The non-transitory computer readable medium of claim 22, wherein the digital signal stream is in a Dolby Digital format. 
     
     
       26. The non-transitory computer readable medium of claim 22, wherein first output is a center channel output. 
     
     
       27. The non-transitory computer readable medium of claim 22, wherein the digital signal stream is a multitrack digital soundtrack.