Synchronized Audio Mixing

Abstract

A first example playback device includes one or more processors and a non-transitory computer-readable medium storing instructions that, when executed by the one or more processors, cause the first playback device to perform functions. The functions include generating a mixed audio signal comprising one or more components of a first audio stream and one or more components of a second audio stream; and playing the mixed audio signal, where the one or more components of the second audio stream of the mixed audio signal played by the first playback device are played in synchrony with a second playback device configured to play the second audio stream. An example non-transitory computer-readable medium and an example method, both related to the first example playback device, are also disclosed herein.

1 . A media playback system comprising:
 a first playback device comprising at least one first audio transducer, a first network interface, and a first housing carrying the at least one first audio transducer and the first network interface;   a second playback device comprising at least one second audio transducer, a second network interface, and a second housing carrying the at least one second audio transducer and the second network interface;   at least one processor; and   data storage including instructions that are executable by the at least one processor such that the media playback system is configured to:
 receive audio content; 
 play back, via the at least one first audio transducer, at least one first audio signal representing at least a first portion of the audio content; 
 play back, via the at least one second audio transducer, at least second audio signal representing at least a second portion of the audio content in synchrony with playback of the at least one first audio signal on the first playback device; 
 receive additional audio content; 
 generate at least one third audio signal representing at least the first portion of the audio content and the additional audio content, wherein the instructions that are executable by the at least one processor such that the media playback system is configured to generate the at least one third audio signal comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the first portion of the audio content with the additional audio content; 
 generate at least one fourth audio signal representing at least the second portion of the audio content and the additional audio content, wherein the instructions that are executable by the at least one processor such that the media playback system is configured to generate the at least one fourth audio signal comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the second portion of the audio content with the additional audio content; 
 play back the at least one third audio signal via the at least one first audio transducer; and 
 play back the at least one fourth audio signal via the at least one second audio transducer in synchrony with playback of the at least one third audio signal on the first playback device. 
   
     
     
         2 . The media playback system of  claim 1 , wherein the audio content comprises a first channel and a second channel of multi-channel audio, wherein the additional audio content comprises a center channel of the multi-channel audio, wherein the instructions that are executable by the at least one processor such that the media playback system is configured to mix the first portion of the audio content with the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the first channel and the center channel, and wherein the instructions that are executable by the at least one processor such that the media playback system is configured to mix the second portion of the audio content with the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the second channel and the center channel. 
     
     
         3 . The media playback system of  claim 2 , wherein the first playback device comprises a high-definition multimedia interface (HDMI) port, and wherein the instructions that are executable by the at least one processor such that the media playback system is configured to receive the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to receive the additional audio content via the HDMI port. 
     
     
         4 . The media playback system of  claim 1 , wherein the audio content comprises a first channel and a second channel of multi-channel audio, wherein the additional audio content comprises an audio notification, wherein the instructions that are executable by the at least one processor such that the media playback system is configured to mix the first portion of the audio content with the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the first channel and the audio notification, and wherein the instructions that are executable by the at least one processor such that the media playback system is configured to mix the second portion of the audio content with the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the second channel and the audio notification. 
     
     
         5 . The media playback system of  claim 4 , wherein the first playback device comprises a high-definition multimedia interface (HDMI) port, wherein the instructions that are executable by the at least one processor such that the media playback system is configured to receive the audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to receive the audio content via the HDMI port, and wherein the instructions that are executable by the at least one processor such that the media playback system is configured to receive the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to receive the additional audio content via the first network interface. 
     
     
         6 . The media playback system of  claim 1 , wherein the first housing of the first playback device is configured for out-loud playback, wherein the second housing of the second playback device is formed into headphones, and wherein the at least one second audio transducer comprises multiple audio transducers carried by the headphones. 
     
     
         7 . The media playback system of  claim 6 , wherein the instructions are executable by the at least one processor such that the media playback system is further configured to:
 determine that particular samples of the at least one fourth audio signal exceed a first threshold level; and   reduce levels of the particular samples below the first threshold level.   
     
     
         8 . The media playback system of  claim 7 , wherein the instructions are executable by the at least one processor such that the media playback system is further configured to:
 determine that particular samples of the at least one third audio signal exceed a second threshold level that is higher than the first threshold level; and   reduce levels of the particular samples below the second threshold level.   
     
     
         9 . The media playback system of  claim 8 , wherein the instructions that are executable by the at least one processor such that the media playback system is configured to reduce levels of the particular samples below the first threshold level comprise instructions that are executable by the at least one processor such that the media playback system is configured to:
 apply at least one scaling factor to the particular samples of the at least one fourth audio signal.   
     
     
         10 . The media playback system of  claim 1 , wherein the at least one processor comprises a first processor that is carried in the first housing and a second processor that is carried in the second housing, and wherein the instructions that are executable by the at least one processor such that the media playback system is configured to mix the first portion of the audio content with the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the first portion of the audio content with the additional audio content via the first processor, and wherein the instructions that are executable by the at least one processor such that the media playback system is configured to mix the second portion of the audio content with the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the second portion of the audio content with the additional audio content via the second processor. 
     
     
         11 . The media playback system of  claim 1 , wherein the instructions are executable by the at least one processor such that the media playback system is further configured to:
 send, via the first network interface to the second playback device, the at least one second audio signal representing at least a second portion of the audio content; and   receive, via the second network interface, the at least one second audio signal.   
     
     
         12 . The media playback system of  claim 11 , wherein the instructions are executable by the at least one processor such that the media playback system is further configured to:
 send, via the first network interface to the second playback device, the at least one fourth audio signal representing at least a second portion of the audio content; and   receive, via the second network interface, the at least one fourth audio signal.   
     
     
         13 . A method to be performed by a media playback system comprising a first playback device and a second playback device, the method comprising:
 receiving audio content;   playing back, via at least one first audio transducer, at least one first audio signal representing at least a first portion of the audio content, wherein the first playback device comprises the at least one first audio transducer and a first housing carrying the at least one first audio transducer;   playing back, via at least one second audio transducer, at least second audio signal representing at least a second portion of the audio content in synchrony with playback of the at least one first audio signal on the first playback device, wherein the second playback device comprises the at least one second audio transducer and a second housing carrying the at least one second audio transducer;   receiving additional audio content;   generating at least one third audio signal representing at least the first portion of the audio content and the additional audio content, wherein generating the at least one third audio signal comprises mixing the first portion of the audio content with the additional audio content;   generating at least one fourth audio signal representing at least the second portion of the audio content and the additional audio content, wherein generating the at least one fourth audio signal comprises mixing the second portion of the audio content with the additional audio content;   playing back the at least one third audio signal via the at least one first audio transducer; and   playing back the at least one fourth audio signal via the at least one second audio transducer in synchrony with playback of the at least one third audio signal on the first playback device.   
     
     
         14 . The method of  claim 13 , wherein the audio content comprises a first channel and a second channel of multi-channel audio, wherein the additional audio content comprises a center channel of the multi-channel audio, wherein mixing the first portion of the audio content with the additional audio content comprises mixing the first channel and the center channel, and wherein mixing the second portion of the audio content with the additional audio content comprises mixing the second channel and the center channel. 
     
     
         15 . The method of  claim 13 , wherein the audio content comprises a first channel and a second channel of multi-channel audio, wherein the additional audio content comprises an audio notification, wherein mixing the first portion of the audio content with the additional audio content comprises mixing the first channel and the audio notification, and wherein mixing the second portion of the audio content with the additional audio content comprises mixing the second channel and the audio notification. 
     
     
         16 . The method of  claim 13 , further comprising:
 determining that particular samples of the at least one fourth audio signal exceed a first threshold level; and   reducing levels of the particular samples below the first threshold level.   
     
     
         17 . The method of  claim 13 , further comprising:
 sending, via a first network interface to the second playback device, the at least one fourth audio signal representing at least a second portion of the audio content, wherein the first playback device comprises the first network interface; and   receiving, via a second network interface, the at least one fourth audio signal, wherein the second playback device comprises the second network interface.   
     
     
         18 . A tangible, non-transitory computer-readable medium comprising program instructions that are executable by at least one processor such that a media playback system comprising a first playback device and a second playback device is configured to:
 receive audio content;   play back, via at least one first audio transducer, at least one first audio signal representing at least a first portion of the audio content, wherein the first playback device comprises the at least one first audio transducer and a first housing carrying the at least one first audio transducer;   play back, via at least one second audio transducer, at least second audio signal representing at least a second portion of the audio content in synchrony with playback of the at least one first audio signal on the first playback device, wherein the second playback device comprises the at least one second audio transducer and a second housing carrying the at least one second audio transducer;   receive additional audio content;   generate at least one third audio signal representing at least the first portion of the audio content and the additional audio content, wherein the instructions that are executable by the at least one processor such that the media playback system is configured to generate the at least one third audio signal comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the first portion of the audio content with the additional audio content;   generate at least one fourth audio signal representing at least the second portion of the audio content and the additional audio content, wherein the instructions that are executable by the at least one processor such that the media playback system is configured to generate the at least one fourth audio signal comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the second portion of the audio content with the additional audio content;   play back the at least one third audio signal via the at least one first audio transducer; and   play back the at least one fourth audio signal via the at least one second audio transducer in synchrony with playback of the at least one third audio signal on the first playback device.   
     
     
         19 . The tangible, non-transitory computer-readable medium of  claim 18 , wherein the audio content comprises a first channel and a second channel of multi-channel audio, wherein the additional audio content comprises a center channel of the multi-channel audio, wherein the instructions that are executable by the at least one processor such that the media playback system is configured to mix the first portion of the audio content with the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the first channel and the center channel, and wherein the instructions that are executable by the at least one processor such that the media playback system is configured to mix the second portion of the audio content with the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the second channel and the center channel. 
     
     
         20 . The tangible, non-transitory computer-readable medium of  claim 18 , wherein the audio content comprises a first channel and a second channel of multi-channel audio, wherein the additional audio content comprises an audio notification, wherein the instructions that are executable by the at least one processor such that the media playback system is configured to mix the first portion of the audio content with the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the first channel and the audio notification, and wherein the instructions that are executable by the at least one processor such that the media playback system is configured to mix the second portion of the audio content with the additional audio content comprise instructions that are executable by the at least one processor such that the media playback system is configured to mix the second channel and the audio notification.