Synchronizing Mobile TV Streaming via NTP Reference Clock Recovery
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Solution Overview
Problem
IP-Based mobile TV systems face challenges in synchronizing the rendering of streaming services across multiple user terminals due to performance differences and lack of standard methods for determining the exact rendering time, leading to asynchronous playback.
Innovation Solution
A mobile TV system that includes an IP-based server set transmitting Network Time Protocol (NTP) time stamps and synchronization clocks, allowing each terminal to recover an NTP reference clock and adjust for synchronization time differences to ensure synchronized rendering of RTP streaming services.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RTP protocol is used for unicast streaming service in IP-based mobile TV system, then streaming service can be transmitted to user terminals, but synchronization of rendering the same streaming service on different mobile user terminal devices in broadcast or multicast transmission is not achieved
Solution Approach 1:
The patent introduces an intermediary synchronization mechanism that mediates between the RTP streaming transmission and the rendering process on different terminals. A synchronization server or network entity acts as an intermediary to distribute synchronization information (such as presentation time stamps, synchronization packets) to all receiving terminals, ensuring that broadcast/multicast transmission can proceed while rendering synchronization is maintained across all devices.
Solution Approach 2:
The patent applies preliminary action by pre-synchronizing clocks and time references before streaming begins. Synchronization information is prepared and distributed in advance, and terminals adjust their local clocks and buffering strategies beforehand to ensure that when broadcast/multicast transmission occurs, all devices are pre-aligned for synchronized rendering.
2Productivity
If different mobile user terminal devices receive the same streaming service, then service coverage is expanded, but performance differences cause different initial delays for rendering leading to asynchronous playback
Solution Approach 1:
The patent changes key parameters such as buffering duration, decoding speed, and presentation time stamps based on the specific performance characteristics of each terminal device. By dynamically adjusting these parameters according to device capabilities (processor speed, memory, decoder performance), the system maintains rendering time consistency across devices with different performance levels while preserving broad service coverage.
Solution Approach 2:
The patent applies local quality by tailoring the streaming service delivery to each terminal's specific performance characteristics. Different terminals receive customized synchronization information and rendering parameters suited to their individual capabilities, ensuring that each device achieves optimal synchronized playback performance according to its own quality level rather than forcing uniform treatment.
3Measurement precision
If NTP time stamps are used for time synchronization, then time reference can be provided, but the clock and time recorded by NTP time stamps are not strictly defined causing asynchronous rendering
Solution Approach 1:
The patent implements feedback mechanisms where terminals report their actual rendering times and synchronization status back to a central server or control entity. Based on this feedback, the system adjusts and refines the NTP time stamp distribution, correcting drift and synchronization errors. This closed-loop feedback ensures that time reference accuracy is continuously maintained and translated into reliable rendering synchronization across all devices.
Data Source
AI summary
An Internet Protocol (IP)-based mobile TV system and a method for synchronizing the rendering of a streaming service are provided. In the IP-based mobile TV system, a plurality of mobile terminals receives a streaming service from network equipment, along with both a sequence of Network Time Protocol (NTP) time stamps corresponding to the streaming service and a synchronization clock. Each mobile terminal recovers an NTP reference clock for rendering the received streaming service according to both the synchronization clock and a synchronization time difference value, and then renders the received streaming service according to both the recovered NTP reference clock and the received NTP time stamps. Accordingly, the plurality of mobile terminals in the IP-based mobile TV system is able to render the received streaming service synchronously.