Audio Rate Adjustment Mechanism for Underflow Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In MPEG audio/video systems, displaying audio in a time base different from its source can lead to underflow or overflow conditions, particularly when switching between main and picture-in-picture (PIP) audio without synchronizing the video, requiring a mechanism to control audio rate adjustment.
Innovation Solution
A dual real-time audio/video system with two decoders, each generating a time base for display timing, implements a control mechanism to adjust audio samples by comparing source and display time bases, adding or removing samples as necessary to match rates, using techniques like duplication or blending to prevent underflow or overflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If audio is displayed in a time base different from its source to enable flexible switching between main and PIP audio, then adaptability is improved, but underflow or overflow conditions occur causing system instability
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring the time base difference between source and display audio, and dynamically adjusting the audio sample rate accordingly. The system calculates the PPM (parts per million) difference and uses this feedback to control the audio rate adjustment, ensuring that audio data flows at the correct rate to prevent underflow or overflow conditions while maintaining the ability to switch between different audio sources.
2Reliability
If audio rate adjustment is implemented to prevent underflow or overflow, then system stability is improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent employs a self-service approach where the audio rate adjustment mechanism automatically monitors and corrects its own operation. The system self-adjusts the audio sample rate by comparing the source time base with the display time base, and autonomously applies the necessary rate conversion without requiring external intervention or complex external control systems. This reduces overall device complexity while maintaining stability.
3Reliability
If time base synchronization is maintained between audio and video to ensure stable playback, then system stability is improved, but adaptability to display audio from different sources is reduced
Solution Approach 1:
The patent segments the audio processing into two independent time base systems: the source time base (from the audio transport stream) and the display time base (from the video transport stream). By separating these time bases and allowing independent operation with controlled conversion between them, the system maintains stable video playback while enabling flexible switching between different audio sources. The audio rate adjustment mechanism acts as a bridge between these segmented time bases.
Data Source
AI summary
A system and method for controlling rate adjustment of audio data to prevent underflow or overflow. In a dual audio/video system, a device can receive two input transport streams. To prevent underflow or overflow of audio data when audio data from a first transport stream is displayed in accordance with a sample rate derived from a second transport stream, a control for rate adjustment is used to match the source sample rate with the display rate. This rate adjustment module can be designed to add or drop audio samples based on a time base comparison or on a STC, PTC, and display rate comparison.