Digital Radio Audio Blending With Loudness Gain Alignment
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Solution Overview
Problem
In digital radio broadcasting, especially in IBOC systems, the transition between analog and digital audio signals during blending can result in abrupt changes in loudness due to misalignment of audio levels and processing differences, affecting the listening experience.
Innovation Solution
A method involving the separation of analog and digital audio signals, calculation of short and long-term average gains, and adjustment of digital gain parameters to align the loudness levels, ensuring a smooth transition by using a short time interval for initial alignment and a longer interval for long-term matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If analog and digital audio signals are blended during transition, then continuity of audio program is preserved, but abrupt changes in loudness occur due to level misalignment
Solution Approach 1:
The patent applies preliminary action by calculating and storing the loudness difference between analog and digital signals before the blend transition occurs. The processor determines the loudness of both signals, calculates their difference, and stores this value for use during the actual blend, ensuring that the loudness alignment is prepared in advance to prevent abrupt changes.
Solution Approach 2:
The patent implements feedback by using the calculated loudness difference to adjust the digital signal level during blending. The system continuously monitors the loudness characteristics and uses the stored loudness difference value to compensate for level mismatches, creating a closed-loop control that maintains consistent perceived loudness throughout the transition.
2Adaptability or versatility
If digital signal processing is performed separately from analog processing, then processing flexibility is improved, but time alignment between signals becomes difficult
Solution Approach 1:
The patent replaces mechanical time alignment methods with digital signal processing techniques. The processor calculates the loudness of both analog and digital signals and uses this information to determine the appropriate alignment, substituting physical timing adjustments with computational analysis and correction.
Solution Approach 2:
The patent applies parameter changes by using loudness measurements as a basis for time alignment adjustments. Instead of relying on fixed timing parameters, the system dynamically determines alignment based on the loudness characteristics of the signals, allowing flexible adjustment of timing parameters to achieve optimal synchronization.
3Speed
If blend transition time is kept short, then response speed is improved, but loudness misalignment becomes more noticeable
Solution Approach 1:
The patent prepares the loudness difference value in advance before the blend transition begins. By calculating and storing this parameter beforehand, the system can execute a rapid blend transition without sacrificing loudness matching accuracy, as the correction factor is already determined and ready for immediate application.
Solution Approach 2:
The patent implements dynamic adjustment of digital signal levels based on the calculated loudness difference. During the blend transition, the system dynamically modifies the digital signal amplitude using the pre-calculated loudness compensation factor, allowing the transition to be both fast and precise in maintaining loudness consistency.
Data Source
AI summary
A method for processing a digital audio broadcast signal includes: separating an analog audio portion and a digital audio portion of the digital audio broadcast signal; determining the loudness of the analog audio portion and the digital audio portion over a first short time interval; using the loudness of the analog and digital audio portions to calculate a short term average gain; determining a long term average gain; converting one of the long term average gain or the short term average gain to dB; if an output has been blended to digital, adjusting a digital gain parameter by a preselected increment to produce a digital gain parameter; if an output has not been blended to digital, setting the digital gain parameter to the short term average gain; providing the digital gain parameter to an audio processor; and repeating the above steps using a second short time interval.