Smart line-in processing in a group

1. A playback device comprising: a line-in connector configured to receive a first audio signal; a network interface; a processor; and a tangible, non-transitory computer readable storage medium having stored therein instructions executable by the processor, wherein the instructions, when executed by the processor, cause the playback device to perform functions comprising: playback a second audio signal: while playing back the second audio signal, determining that the first audio signal is present at the line-in connector; and in response to determining that the first audio signal is present at the line-in connector, (i) ceasing playback of the second audio signal being played by the playback device, wherein the second audio signal is not present at the line-in connector, (ii) causing the playback device to play at least a first portion of the first audio signal, and (iii) causing the playback device to transmit, via the network interface, at least a second portion of the first audio signal to another playback device for synchronous playback.

2. The playback device of claim 1 , wherein transmitting at least the second portion of the first audio signal to another playback device comprises transmitting all portions of the first audio signal to another playback device.

3. The playback device of claim 2 , wherein causing the playback device to play at least the first portion of the first audio signal comprises causing the playback device to play all portions of the first audio signal.

4. The playback device of claim 2 , wherein causing the playback device to play at least the first portion of the first audio signal comprises causing the playback device to play a subset of channels of the first audio signal.

5. The playback device of claim 4 , wherein the subset of channels of the first audio signal consists of one of a left channel or a right channel.

6. The playback device of claim 1 , wherein transmitting at least the second portion of the first audio signal to another playback device comprises transmitting a subset of channels of the first audio signal to another playback device.

7. The playback device of claim 6 , wherein the subset of channels of the first audio signal is a first subset of channels of the first audio signal, and wherein causing the playback device to play at least the first portion of the first audio signal comprises causing the playback device to play a second subset of channels of the first audio signal, wherein the first subset of channels is different from the second subset of channels.

8. The playback device of claim 1 , wherein the playback device is a first playback device and the another playback device is a second playback device, and wherein the instructions, when executed by the processor, cause the playback device to perform further functions comprising:

causing the playback device to transmit, via the network interface, at least a third portion of the first audio signal to a third playback device.

9. The first playback device of claim 8 , wherein the first portion of the first audio signal, the second portion of the first audio signal, and the third portion of the first audio signal are the same.

10. The first playback device of claim 8 , wherein the first portion of the first audio signal, the second portion of the first audio signal, and the third portion of the first audio signal are different.

11. The playback device of claim 1 , wherein the instructions, when executed by the processor, cause the playback device to perform further functions comprising:

causing the playback device to receive a command to form a group with the another playback device.

12. The playback device of claim 11 , wherein the command to form the group with the another playback device comprises a command to form a stereo pair with the another playback device.

13. The playback device of claim 1 , wherein the instructions, when executed by the processor, cause the playback device to perform further functions comprising:

causing the playback device to generate timing information associated with the first audio signal; and

cause the playback device to transmit, via the network interface, the generated timing information to the another playback device.

14. The playback device of claim 1 , wherein transmitting at least the second portion of the first audio signal comprises:

sampling the first audio signal; and

generating data packets comprising at least the second portion of the first audio signal.

15. The playback device of claim 1 , wherein the instructions, when executed by the processor, further cause the playback device to perform further functions comprising:

ceasing playback of the first portion of the first audio signal;

causing the playback device to play the second audio signal; and

while playing the second audio signal, transmitting the first audio signal to the another playback device.

16. The playback device of claim 1 , wherein the first portion of the first audio signal and the second portion of the first audio signal are the same.

17. A method comprising: determining, by a playback device, that a first audio signal is present at a line-in connector; and in response to determining that the first audio signal is present at the line-in connector, the playback device: (i) ceasing playback of a second audio signal being played by the playback device, wherein the second audio signal is not present at the line-in connector, (ii) playing at least a first portion of the first audio signal, and (iii) transmitting, via a network interface, at least a second portion of the first audio signal to another playback device for synchronous playback.

18. The method of claim 17 , wherein transmitting at least the second portion of the first audio signal to another playback device comprises transmitting all portions of the first audio signal to another playback device, and wherein causing the playback device to play at least the first portion of the first audio signal comprises causing the playback device to play a subset of channels of the first audio signal.

19. The method of claim 17 , wherein playing at least the first portion of the first audio signal comprises playing a subset of channels of the first audio signal, wherein the subset of channels of the first audio signal is a first subset of channels of the first audio signal, wherein transmitting at least the second portion of the first audio signal to another playback device comprises transmitting a subset of channels of the first audio signal to another playback device, and wherein causing the playback device to play at least the first portion of the first audio signal comprises causing the playback device to play a second subset of channels of the first audio signal, wherein the first subset of channels is different from the second subset of channels.

20. Tangible, non-transitory computer readable storage media having stored therein instructions executable by a processor, wherein the instructions, when executed by the processor, cause a playback device to perform a method comprising:

playback a second audio signal;

while playing back the second audio signal, determining that a first audio signal is present at an line-in connector; and

in response to determining that the first audio signal is present at the line-in connector, (i) ceasing playback of the second audio signal being played by the playback device, wherein the second audio signal is not present at the line-in connector, (ii) causing the playback device to play at least a first portion of the first audio signal, and (iii) causing the playback device to transmit, via a network interface, at least a second portion of the first audio signal to another playback device.