Capture Buffer Control for Caption Carriage Switch
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Solution Overview
Problem
The unpredictable switch between SMPTE 333M and SMPTE 334M caption carriage methods in digital television closed captioning can cause capture buffer underflow, impacting the efficiency of EIA-708 caption distribution in high-definition television environments.
Innovation Solution
A buffer control method and system that monitors and manages the caption buffer by detecting switches between SMPTE 333M and SMPTE 334M, using a circular buffer and buffer control program to ensure continuous caption data capture and encoding, preventing underflow by adjusting the read and write points accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the system handles unpredictable caption carriage switch between SMPTE 333M and SMPTE 334M, then the adaptability is improved, but the capture buffer may underflow causing reliability deterioration
Solution Approach 1:
The system pre-loads caption data into the capture buffer before actual encoding occurs. By anticipating future caption data needs and storing them in advance, the buffer maintains sufficient data even when carriage methods switch unpredictably, preventing underflow conditions while supporting multiple caption formats
Solution Approach 2:
The capture buffer acts as an intermediary between the caption data source and the encoding process. It decouples the timing and format of incoming captions from the encoding requirements, allowing the system to handle carriage switches smoothly by mediating data flow and preventing direct buffer underflow
2Reliability
If the system monitors and manages caption buffer dynamically, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The system continuously monitors the capture buffer's data level and uses this feedback to control the reading rate. When the buffer approaches underflow conditions, the system adjusts its operation to prevent data exhaustion, creating a self-regulating mechanism that maintains reliability through simple feedback-based control
Solution Approach 2:
The buffer control system automatically manages itself by monitoring its own state and making adjustments without external intervention. The system self-regulates the caption data flow and buffer management, reducing the need for complex external control mechanisms while maintaining reliable operation
Data Source
AI summary
A system, method, and computer readable medium for avoiding underflow of a caption buffer in a digital video encoding device. The method receives a sequence of digital video frames, and captions that correspond to the digital video frames in the sequence. The method receives first captions in a first caption carriage, and encodes the first captions, and the corresponding digital video frames, in a compressed video format. The method detects a switch from the first caption carriage to a second caption carriage, and stores second captions in the capture buffer, where each second caption is received in the second caption carriage and corresponds to one of the digital video frames in the sequence. The method examines the capture buffer and the second captions to determine whether underflow of the capture buffer is present or absent. When underflow is absent, the method encodes the second captions, and the corresponding digital video frames, in the compressed video format.