Parametric Audio DRC Reversal for Seamless Bitrate Switching
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Solution Overview
Problem
Existing adaptive distribution formats for audiovisual media struggle with bandwidth efficiency, computational efficiency, error resilience, algorithmic delay, and noticeable bitrate switching events, while also facing challenges in maintaining backward compatibility with legacy decoders.
Innovation Solution
A coding format that enables adaptive bitrate distribution, allowing seamless transitions between higher-bitrate and lower-bitrate modes during decoding, while ensuring consistent dialogue levels and compatibility with both legacy and modern decoders through dynamic range control (DRC) techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If adaptive bitrate distribution is implemented, then bandwidth efficiency is improved, but computational complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing DRC parameter adjustments that will be needed during bitrate switching. The system prepares compensation values in advance based on the relationship between different bitrates and their corresponding dynamic range characteristics, so that when switching occurs, the pre-computed parameters can be immediately applied without real-time computation, thus reducing computational complexity while maintaining bandwidth efficiency.
Solution Approach 2:
The patent implements dynamics by creating a dynamic DRC parameter adjustment mechanism that adapts to different bitrate conditions. The system dynamically selects and applies appropriate DRC parameters based on the current bitrate mode, allowing the distribution format to flexibly respond to changing network conditions while maintaining consistent dialogue levels. This dynamic adaptation resolves the contradiction by enabling efficient bitrate switching without requiring complex real-time computations.
2Adaptability or versatility
If bitrate switching is implemented, then adaptability is improved, but perceptible artefacts increase
Solution Approach 1:
The patent applies parameter changes by systematically adjusting DRC parameters in response to bitrate changes. When switching between different bitrates, the system modifies the DRC gain parameters to compensate for the dynamic range variations that would otherwise be perceptible. This parameter adjustment ensures that dialogue levels remain consistent across bitrate transitions, eliminating artefacts while preserving bitrate adaptability.
Solution Approach 2:
The patent implements feedback mechanisms by monitoring bitrate switching events and automatically applying compensatory DRC adjustments. The system detects when bitrate changes occur and responds by adjusting the dynamic range parameters to maintain consistent audio output characteristics. This closed-loop feedback approach ensures that artefacts from bitrate switching are minimized while the system retains full adaptability to different network conditions.
3Manufacturing precision
If DRC parameter adjustment is implemented, then dialogue level consistency is improved, but device complexity increases
Solution Approach 1:
The patent reduces decoder complexity through preliminary action by having the encoder pre-calculate and embed DRC adjustment parameters in the bitstream. The decoder simply needs to extract and apply these pre-computed parameters rather than performing complex real-time calculations. This approach maintains precise dialogue level consistency across different bitrate modes while keeping the decoder implementation relatively simple.
Solution Approach 2:
The patent uses an intermediary approach by introducing DRC parameter data structures that act as mediators between the encoder and decoder. These parameter structures serve as a bridge, carrying the necessary adjustment information from the encoder to the decoder in a standardized format. This intermediary mechanism simplifies the decoder's task while ensuring accurate dialogue level consistency, as the decoder only needs to interpret and apply the provided parameters rather than generate them independently.
Data Source
AI summary
On the basis of a bitstream (P), an n-channel audio signal (X) is reconstructed by deriving an m-channel core signal (Y) and multichannel coding parameters (α) from the bitstream, where 1≤m<n. Also derived from the bitstream are pre-processing dynamic range control, DRC, parameters (DRC2) quantifying an encoder-side dynamic range limiting of the core signal. The n-channel audio signal is obtained by parametric synthesis in accordance with the multichannel coding parameters and while cancelling any encoder-side dynamic range limiting based on the pre-processing DRC parameters.In particular embodiments, the reconstruction further includes use of compensated post-processing DRC parameters quantifying a potential decoder-side dynamic range compression. Cancellation of an encoder-side range limitation and range compression are preferably performed by different decoder-side components. Cancellation and compression may be coordinated by a DRC pre-processor.