Method and system for synchronization of content rendering

Abstract

A method and system for synchronizing the rendering of content at various rendering devices. Each rendering device has a device time and a rendering time. The synchronization system designates one of the rendering devices as a master rendering device and designates all other rendering devices as slave rendering devices. Each slave rendering device adjusts the rendering of its content to keep it in synchronization with the rendering of the content at the master rendering device. The master rendering device sends a message with its rendering time and corresponding device time to the slave rendering devices. Each slave rendering device, upon receiving the message from the master rendering device, determines whether it is synchronized with the master rendering time. If not, the slave rendering device adjusts the rendering of its content to compensate for the difference between the master rendering time and the slave rendering time.

1 . A method for synchronizing the rendering of content at a plurality of devices, the content having a rendering time, the method comprising:
 designating one of the devices as a master device and the other devices as slave devices;   sending to each device content to be rendered at that device synchronized with the content sent to the other devices;   sending from the master device to the slave devices an indication of when the master device renders content corresponding to a rendering time; and   after receiving the indication at a slave device, adjusting based on the received indication the rendering of the content at the slave device to account for variation between when the master device and the slave device render content that should be rendered at the same time.   
     
     
         2 . The method of  claim 1  wherein the indication sent from the master device to the slave devices includes a master device time at which the master device renders content corresponding to a rendering time. 
     
     
         3 . The method of  claim 2  wherein the indication sent from the master device to the slave devices includes the corresponding rendering time. 
     
     
         4 . The method of  claim 2  wherein the corresponding rendering time is a default rendering time. 
     
     
         5 . The method of  claim 2  wherein the corresponding rendering time is time zero. 
     
     
         6 . The method of  claim 2  wherein the adjusting includes:
 calculating a difference between the master device time and a slave device time that correspond to the rendering time.   
     
     
         7 . The method of  claim 2  wherein the adjusting includes:
 calculating a difference between a master rendering time and a slave rendering time that correspond to the same master and slave device times.   
     
     
         8 . The method of  claim 2  wherein the adjusting includes:
 adjusting a device time so that the master device time and the slave device time are in the same time domain;   calculating a master start time for the master device from the master device time that is in the same time domain as the slave device time and a master rendering time;   calculating a slave start time for the slave device from the slave device time that is in the same time domain as the master device time and a slave rendering time; and   calculating the difference between the slave start time and the master start time.   
     
     
         9 . The method of  claim 1  wherein the sending of the indication from the master device to the slave devices occurs at various times so that the slave devices can adjust the rendering of the content as appropriate. 
     
     
         10 . The method of  claim 1  wherein the adjusting accounts for variations in the time domain of the master device and the slave device. 
     
     
         11 . The method of  claim 1  wherein the content is sent from a single source to the master device and the slave devices. 
     
     
         12 . The method of  claim 1  wherein the content is sent from different sources to the master device and the slave devices. 
     
     
         13 . The method of  claim 12  including receiving a rendering time adjustment that indicates a difference in a master rendering time and a slave rendering time of content that is to be synchronized. 
     
     
         14 . The method of  claim 13  wherein a user specifies the rendering time adjustment. 
     
     
         15 . The method of  claim 14  wherein the user specifies the rendering time adjustment by indicating the amount of time the master device and the slave device are out of synchronization. 
     
     
         16 . A method for synchronizing rendering of content at devices, each device having a device time and a rendering time, the device time of a device being in a time domain of the device, the method comprising:
 designating one of the devices as a master device and the one or more other devices as slave devices;   sending to each device content to be rendered at that device synchronized with the content sent to the other devices;   sending from the master device to the one or more slave devices a master device time corresponding to a master rendering time of the master device; and   upon receiving the sent master device time at a slave device, adjusting the rendering of the content at the slave device to account for a difference in a slave rendering time and a master rendering time calculated based on the master device time adjusted for a difference in time domains of the slave device and the master device.   
     
     
         17 . The method of  claim 16  wherein the difference in a slave rendering time and a master rendering time is calculated by:
 converting the master device time to a time frame of the slave device;   calculating a master start time for the master device from the converted master device time and the master rendering time;   calculating a slave start time for the slave device from the slave device time and the slave rendering time; and   calculating the difference between the slave start time and the master start time.   
     
     
         18 . The method of  claim 16  wherein the sending from the master device to the slave devices the master device time and the master rendering time occurs at various times so that the slave devices can adjust the rendering of the content as appropriate. 
     
     
         19 . The method of  claim 16  wherein the content is sent from different sources to the master device and the slave devices. 
     
     
         20 . The method of  claim 19  including receiving a rendering time adjustment that indicates a difference in a master rendering time and a slave rendering time of content that is to be synchronized. 
     
     
         21 . The method of  claim 20  wherein a user specifies the rendering time adjustment. 
     
     
         22 . The method of  claim 21  wherein the user specifies the rendering time adjustment by indicating the amount of time the master device and the slave device are out of synchronization. 
     
     
         23 . A method for synchronizing rendering of content at devices, each device having a device time and a rendering time, the device time of a device being in a time domain of the device, the method comprising:
 designating one of the devices as a master device and the one or more other devices as slave devices; and   for each slave device,
 calculating a difference in a master rendering time of the master device and slave rendering time of the slave device based on a master device time adjusted for a difference in time domains of the slave device and the master device; and 
 rendering content at the slave device to account for the calculated difference. 
   
     
     
         24 . The method of  claim 23  including sending a master device time and a corresponding master rendering time to each slave device for use in calculating the difference. 
     
     
         25 . The method of  claim 24  wherein the master device sends the master device time and the corresponding master rendering time to the slave devices.