Subtitle Stream Timing Control in Digital Video Broadcasting

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Solution Overview

Problem

Existing subtitle transmission systems in digital video broadcasting struggle with precise display timing control of subtitles on the reception side, particularly when subtitles are transmitted as text character codes rather than bitmap data, lacking accurate timing information.

Innovation Solution

A transmission apparatus that generates a video stream with coded image data and a subtitle stream containing text information and display timing information, using formats like TTML, which is then transmitted together, allowing for precise display timing control on the reception side by including display start timing and duration information within the subtitle stream.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If subtitles are transmitted as text character codes instead of bitmap data, then data transmission efficiency is improved, but display timing control precision deteriorates

Engineering Contradiction:

Improvedata transmission efficiencyVSAvoiddisplay timing control precision

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The subtitle data is segmented into distinct components: text character codes and separate timing information fields. Each subtitle entry is divided into text content, display start time, and display duration, allowing independent processing and transmission of each element while maintaining precise timing control.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Timing information fields act as intermediaries between the text character codes and the display system. These intermediary fields (display start time and display duration) carry the precise timing data needed to control when subtitles should be displayed, resolving the contradiction between efficient text transmission and precise timing control.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If text information is transmitted with timing information using TTML format, then display timing control is improved, but device complexity increases

Engineering Contradiction:

Improvedisplay timing controlVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The timing information fields serve multiple functions: they store display start time, display duration, and can be used for synchronization with video content. This multi-functionality reduces the need for separate control mechanisms, thereby managing device complexity while achieving precise display timing control.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system changes the parameter representation from simple bitmap data to structured text codes with associated timing parameters. By introducing standardized time-related parameters (display start time, display duration) into the subtitle data structure, the system achieves precise timing control while maintaining manageable complexity through parameterization.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3236659B1Transmission device, transmission method, reception device, and reception method

Publication Date: 2020.11.04 SONY GROUP CORP

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AI summary

Display timing control of subtitles is to be excellently performed on a reception side. A video stream having coded image data is generated. A subtitle stream having text information on the subtitles and display timing information is generated. A transport stream containing the video stream and the subtitle stream is transmitted. For example, the display timing information on the subtitles contains information on display start timing and display duration.