Subtitle Packet Timing With TTML Reference Time Synchronization
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Solution Overview
Problem
Existing subtitle transmission methods in broadcasting, such as Digital Video Broadcasting (DVB), face challenges in synchronizing text-based subtitle information with system timing without altering the relative display timing, especially when using Timed Text Markup Language (TTML), as the display timing is independent from system timing management.
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 without changing the 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 can be independently produced for each content, but the display timing does not synchronize with system timing
Solution Approach 1:
The patent introduces reference time information as an intermediary element that bridges the independent TTML subtitle timing and the system timing. This reference time information, included in the packet payload, serves as a mediator that allows the receiver to convert relative display timing into absolute system-synchronized timing without altering the original subtitle content or its relative timing relationships
Solution Approach 2:
The patent adds a temporal dimension by introducing reference time information that connects the relative timing domain of TTML subtitles with the absolute timing domain of system clock. This dimensional transformation enables synchronization while preserving the independence of subtitle production, as the conversion from relative to absolute timing is performed at reception without modifying the original subtitle data
2Reliability
If packet is generated and transmitted in synchronization with sample period, then system timing association is secured, but the display timing of subtitle must be converted from relative to absolute timing
Solution Approach 1:
The patent performs preliminary action by pre-calculating and embedding reference time information in the packet payload before transmission. This reference time information is prepared in advance to facilitate the timing conversion process at the receiver, reducing the complexity of real-time timing calculations and enabling efficient synchronization without complex processing during playback
3Stability of the object's composition
If display timing information is kept as relative timing in TTML package, then the original subtitle timing is preserved, but synchronization with system timing cannot be achieved
Solution Approach 1:
The patent segments the timing information into two distinct parts: the original relative display timing information embedded in the TTML subtitle content, and separate reference time information included in the packet payload. This segmentation allows the relative timing to be preserved for subtitle integrity while the reference time information provides the means for system synchronization, with both segments working together without interfering with each other
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.