Client device and local clock skew compensation method thereof
A local watch skew compensation device of the present invention is a client device which is synchronized with the other client device to provide a time-aware service including: a local time providing unit which supplies first local time data and second local time data in accordance with a local clock; a media scheduling unit which receives first media data and second media data from the other client device, schedules first playout time of the first media data using the first local time data, and schedules second playout time of the second media data using the second local time data; and a skew monitoring unit which requests global time data to a global time server when a difference between the first playout time and the second playout time exceeds a skew threshold value, and the first media data and the second media data are different types of media data.
1. A client device which is synchronized with an other client device to provide a time-aware service, the client device comprising:
a local time providing unit which supplies first local time data and second local time data in accordance with a local clock;
a media scheduling unit which receives first media data and second media data from the other client device, schedules a first playout time of the first media data using the first local time data, and schedules a second playout time of the second media data using the second local time data; and
a skew monitoring unit which requests global time data to a global time server when a skew amount corresponding to a difference between the first playout time and the second playout time exceeds a skew threshold value,
wherein the first media data and the second media data are different types of media data, and the skew threshold value in accordance with types of the first media data and the second media data is stored in a database.
2. The client device of claim 1 , wherein the skew monitoring unit includes:
a skew amount calculating unit which calculates the skew amount between the first media data and the second media data using the first playout time and the second playout time;
a skew amount comparing unit which compares the skew threshold value and the skew amount; and
a global time requesting unit which requests the global time data to the global time server when the skew amount exceeds the skew threshold value.
3. The client device of claim 2 , wherein the skew amount comparing unit compares a value obtained by multiplying a weight value and the skew amount with the skew threshold value.
4. The client device of claim 1 , further comprising:
a local clock compensation unit which receives the global time data to compensate the local clock.
5. The client device of claim 1 , further comprising:
a rendering unit which renders the first media data and the second media data in accordance with the first playout time and the second playout time.
6. The client device of claim 1 , wherein the skew threshold value is a maximum skew value at which a user does not perceive asynchronous rendering of the first media data and the second media data.
7. The client device of claim 1 , wherein the types of the first media data and second media data are one of video and audio type, haptic and video type, and haptic and audio type.
8. The client device of claim 1 , wherein the first media data and the second media data are media data captured from a corresponding sensor of the other client device.
9. A local clock skew compensation method which is performed in a client device which is synchronized with an other client device to provide a time-aware service, the local clock skew compensation method comprising:
receiving first media data and second media data captured by a sensor of the other client device;
scheduling a first playout time of the first media data using a first local time data, and scheduling a second playout time of the second media data using a second local time data; and
compensating a local clock by requesting global time data to a global time server when a skew amount corresponding to a difference between the first playout time and the second playout time exceeds a skew threshold value,
wherein the first media data and the second media data are different types of media data, and the skew threshold value in accordance with types of the first media data and the second media data is stored in a database.
10. The local clock skew compensation method of claim 9 , further comprising:
compensating the local clock of the client device by requesting the global time data to the global time server at a beginning of the time-aware service.
11. The local clock skew compensation method of claim 9 , wherein the skew threshold value is a maximum skew value at which a user does not perceive asynchronous rendering of the first media data and the second media data.
12. The local clock skew compensation method of claim 9 , wherein the types of the first media data and second media data are one of video and audio type, haptic and video type, and haptic and audio type.