Content playback system, playback device, playback control method and program

A playback device comprising:

• a communication portion that communicates data with a server device or an other playback device;
• a memory that memorizes content data received from the server device through the communication portion;
• a playback portion that plays back the content data that is memorized in the memory;
• and
• a synchronized playback control portion that, upon receiving a synchronized playback start command to play back the content data in synchronization by the playback device and an other playback device while the content data is being played back by the playback portion, transmits, to the other playback device through the communication portion, information that pertains to the content data and information that indicates a synchronized playback start time obtained by adding a predetermined additional time to an elapsed playback time for the content data;
• wherein, after a playback preparation completion notification that indicates completion of playback preparation of the content data is received from the other playback device through the communication portion, and when the elapsed playback time for the content data reaches the synchronized playback start time, the synchronized playback control portion transmits a playback start command for the content data to the other playback device through the communication portion.

A playback device comprising:

• a communication portion that communicates data with a server device or an other playback device;
• a memory that memorizes content data received from the server device through the communication portion;
• a playback portion that plays back the content data that is memorized in the memory;
• and
• a synchronized playback control portion that receives, from the other playback device through the communication portion, information that pertains to content data that is being played back on the other playback device and information that indicates a synchronized playback start time obtained by adding a predetermined additional time to an elapsed playback time for the content data;
• starts receiving data that begins from the synchronized playback start time for the content data from the server device based on the information that pertains to the content data and memorizes the content data in the memory;
• transmits, after the data of the content data that is memorized in the memory reaches or exceeds a specified volume, a playback preparation completion notification that indicates completion of playback preparation of the content data to the other playback device through the communication portion;
• and upon receiving a playback start command for the content data from the other playback device after transmission of the playback preparation completion notification, starts playing back the data that begins from the synchronized playback start time for the content data that is memorized in the memory.

A playback control method for a playback device that plays back content data received from a server device in synchronization with at least one playback devices, comprising the steps of:

• playing back, while receiving, content data from the server device;
• transmitting to the other playback device, information that pertains to the content data and information that indicates a synchronized playback start time obtained by adding a predetermined additional time to an elapsed playback time for the content data, upon receiving a synchronized playback command to play back the content data in synchronization by the playback device and the other playback device while the content data playback is in progress;
• receiving, from the other playback device, a playback preparation completion notification that indicates completion of playback preparation of the content data;
• and
• transmitting a playback start command for the content data to the other playback device when the elapsed playback time for the content data reaches the synchronized playback start time after receiving the playback preparation completion notification.

A playback control method for a playback device that plays back content data received from a server device in synchronization with at least one other playback devices, comprising the steps of:

• receiving, from the other playback device, information that pertains to content data that is being played back on the other playback device and information that indicates a synchronized playback start time obtained by adding a predetermined additional time to an elapsed playback time for the content data;
• based on the information that pertains to the content data, starting receiving of data that begins from the synchronized playback start time for the content data from the server device and memorizing the data in a memory;
• transmitting to the other playback device a playback preparation completion notification that indicates completion of playback preparation of the content data after the data of the content data that is memorized in the memory reaches or exceeds a specified volume;
• and
• starting playback of the data that begins from the synchronized playback start time for the content data that is memorized in the memory, upon receiving a playback start command for the content data from the other playback device after transmission of the playback preparation completion notification.