Subtitle Packet Timing Synchronization via Reference Time Segments
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Solution Overview
Problem
Existing subtitle transmission methods in broadcasting, such as Digital Video Broadcasting (DVB), face challenges in synchronizing text subtitle information with system timing without altering the relative display timing, especially when using Timed Text Markup Language (TTML), which can lead to inappropriate subtitle display timing at the reception end.
Innovation Solution
A transmitter and receiver system that generates and transmits packets with a time stamp on a first time axis indicating the start time of a sample period, along with reference time information on a second time axis associated with the display timing, ensuring synchronization with system timing without changing the subtitle's display timing, using a packet structure that includes a TTML segment and a reference time segment, allowing for accurate subtitle display timing control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If subtitle information is transmitted in text-based format (TTML) with relative display timing, then the subtitle content and formatting flexibility are improved, but the synchronization with system timing deteriorates
Solution Approach 1:
The patent introduces a reference time segment as an intermediary element that bridges the TTML subtitle data and the system timing. This reference time segment contains timing information that allows the receiver to convert relative TTML timing into absolute system timing without modifying the original TTML structure, thus maintaining both format flexibility and synchronization accuracy
Solution Approach 2:
The patent adds a temporal dimension by introducing a reference time axis that runs parallel to the TTML timing axis. This allows timing information to be represented in two different reference frames simultaneously - the original relative timing in TTML and the absolute system timing through the reference time segment, enabling conversion between the two without loss of information
2Ease of operation
If display timing in TTML is kept as relative timing for each package, then the independence of subtitle production is improved, but the association with system timing at transmission deteriorates
Solution Approach 1:
The patent segments the timing information into two independent parts: the original relative timing in the TTML subtitle packages and the absolute reference timing in separate reference time segments. This segmentation allows each part to maintain its original characteristics while together they provide both production independence and timing association
Solution Approach 2:
The reference time segment acts as a mediator that connects the independent subtitle production process with the system timing requirements. It provides the necessary timing reference without interfering with the independent creation and formatting of subtitle content
3Reliability
If packets are transmitted in synchronization with sample period, then the system timing coordination is improved, but the complexity of timing management deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calculating and embedding the reference time information in the reference time segment before transmission. This allows the receiver to simply retrieve and use the pre-computed timing reference without performing complex real-time timing calculations, thus maintaining system coordination while reducing operational complexity
Data Source
AI summary
An association with a system timing at the time of transmission is secured without changing a display timing in text information of a subtitle, and a reception side displays the subtitle at an appropriate timing.A packet in which a document of the text information of the subtitle having display timing information is included in a payload is generated and transmitted in synchronization with a sample period. A header of the packet includes a time stamp on a first time axis indicating a start time of the corresponding sample period. The payload of the packet further includes reference time information of a second time axis regarding the display timing associated with the start time of the corresponding sample period.