Variable Bit Rate Audio Encoding Adaptation
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Solution Overview
Problem
As distributors of MPEG-2 transport streams reduce video bit rates, the fraction of total encoder bit rate used for encoding audio increases, leading to a need for reducing audio bit rates without degrading quality, especially in applications where storage and transmission of audio signals are costly.
Innovation Solution
A method and apparatus for producing a variable bit rate framed audio signal by encoding an audio signal into multiple encoded signals at different bit rates and adaptively selecting frames based on criteria such as level, loudness, and psychoacoustic demands to form a final output with minimal quality degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If audio is encoded at constant bit rate, then encoding is simple, but bit rate cannot be reduced without quality degradation
Solution Approach 1:
The patent applies dynamics by transitioning from constant bit rate encoding to variable bit rate encoding. Multiple encoders operate at different bit rates, and the system dynamically selects which encoder output to use based on current audio characteristics. This allows the bit rate to adapt to the actual audio content requirements, reducing overall bit rate while maintaining quality when possible.
Solution Approach 2:
The patent changes the bit rate parameter from fixed to variable. By encoding the same audio signal at multiple different bit rates and then selecting the appropriate one based on psychoacoustic analysis and other criteria, the system optimizes the bit rate parameter dynamically rather than using a static value.
2Quantity of substance
If multiple encoders at different bit rates are used, then bit rate can be optimized, but device complexity increases
Solution Approach 1:
The patent segments the encoding task by dividing it into multiple parallel encoders, each handling a specific bit rate. This segmentation allows independent optimization of each encoder and enables selective combination of their outputs based on current requirements, managing complexity through functional decomposition.
Solution Approach 2:
The system achieves multi-functionality by having multiple encoders that can all process the same input audio signal but produce outputs suitable for different bit rate requirements. The selection mechanism provides universal access to the most appropriate encoding output based on current audio characteristics and transmission constraints.
3Manufacturing precision
If variable bit rate encoding is implemented, then audio quality is maintained at lower bit rates, but processing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-encoding the audio signal at multiple bit rates before transmission or storage. This advance preparation allows the system to have multiple quality levels ready for selection, avoiding the need for complex real-time encoding decisions during playback or transmission.
Solution Approach 2:
The system uses feedback mechanisms by analyzing audio characteristics (such as psychoacoustic models, signal statistics, or quality metrics) and using this information to select the most appropriate encoder output. This closed-loop approach ensures quality is maintained by adapting the bit rate selection based on actual audio content requirements.
Data Source
AI summary
A method and apparatus for producing a variable bit rate audio signal is disclosed. An audio signal is encoded into a plurality of encoded audio signals at different bit rates. A variable bit rate audio signal is produced by selecting between the plurality of encoded audio frames of different bit rates in accordance with a selection criterion.