Audio Encoder Gain Control With Zero-Delay Overload Prevention
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Solution Overview
Problem
Existing gain control techniques in audio encoding cause delays and inaccuracies in error-prone environments, leading to signal distortions and quality loss due to overload conditions.
Innovation Solution
Adaptive gain control methods that determine zero-delay gain parameters using lookahead samples and selective encoding of gain parameters, allowing for smooth transitions and efficient bit allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional gain control techniques are used to determine gain parameters, then gain control can be applied to attenuate signals, but delays are introduced and real-time processing capability is reduced
Solution Approach 1:
The patent uses lookahead samples (future frames) to determine gain parameters for the current frame, allowing the gain control decision to be made in advance without introducing delay. The encoder determines gain parameters using samples from future frames n and n+1 to control the current frame n, effectively performing the gain control action preliminarily without waiting for feedback
Solution Approach 2:
The patent inverts the traditional feedback-based gain control approach by using feedforward control with lookahead samples. Instead of determining gain based on previous frames or feedback from decoded output, the system determines gain parameters by analyzing future frames in advance, reversing the temporal direction of the control signal
2Reliability
If gain control is applied to prevent overload conditions, then encoder overload is avoided, but signal distortions may occur due to delayed or inaccurate gain determination
Solution Approach 1:
By determining gain parameters using lookahead samples before encoding the current frame, the system prevents overload conditions from occurring in the first place. The gain control is applied preliminarily based on predicted signal levels from future frames, eliminating the need for corrective attenuation that would cause distortion
Solution Approach 2:
The patent incorporates feedback mechanisms where the encoder monitors the actual signal levels and adjusts gain parameters accordingly. The system uses feedback from the signal analysis process to refine gain determination, ensuring that overload conditions are prevented while maintaining signal fidelity through continuous adjustment
3Device complexity
If gain parameters from previous frames are used for gain control, then processing is simplified, but error propagation occurs in error-prone environments like cellular transmissions
Solution Approach 1:
The system determines gain parameters preliminarily using lookahead samples from future frames before transmission errors can occur. This feedforward approach eliminates dependence on previous frames that may have been corrupted by transmission errors, making the gain control inherently more error-resilient without significantly increasing processing complexity
Solution Approach 2:
The patent segments the gain control process into independent frame-by-frame determinations based on local signal characteristics in lookahead samples. Each frame's gain parameter is determined independently using only its own and future frame samples, preventing error propagation from previous frames while maintaining processing efficiency
Data Source
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AI summary
A method for performing gain control on audio signals is provided. In some implementations, the method involves determining downmixed signals associated with one or more downmix channels associated with a current frame of an audio signal to be encoded. In some implementations, the method involves determining whether an overload condition exists for an encoder. In some implementation, the method involves determining a gain parameter. In some implementations, the method involves determining at least one gain transition function based on the gain parameter and a gain parameter associated with a preceding frame of the audio signal. In some implementations, the method involves applying the at least one gain transition function to one or more of the downmixed signals. In some implementations, the method involves encoding the downmixed signals in connection with information indicative of gain control applied to the current frame.