Parametric Audio Decoding With Reversible DRC for Bitrate Switching
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Solution Overview
Problem
Existing adaptive distribution formats for audiovisual media struggle with maintaining backward compatibility and often result in dynamic range inconsistencies during bitrate switching, especially in legacy equipment.
Innovation Solution
A method and system that encode and decode audiovisual signals using pre-processing and post-processing dynamic range control (DRC) parameters, allowing for seamless bitrate transitions by canceling or adjusting dynamic range limitations, ensuring consistent dialogue levels across different equipment types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If adaptive bitrate coding is used to improve bandwidth efficiency, then bandwidth efficiency is improved, but dynamic range inconsistencies occur during bitrate switching
Solution Approach 1:
The encoder pre-calculates and embeds DRC parameters in the bitstream before decoding occurs. These parameters indicate the dynamic range adjustment needed when switching between bitrate modes, allowing the decoder to proactively adjust rather than reactively correct dynamic range inconsistencies
Solution Approach 2:
The system uses embedded DRC parameters as feedback information that guides the decoder's dynamic range adjustment process. The parameters provide continuous guidance throughout playback, enabling real-time correction of dynamic range issues during bitrate transitions
2Adaptability or versatility
If legacy decoder compatibility is maintained, then backward compatibility is improved, but dynamic range control capability is reduced
Solution Approach 1:
DRC parameters serve as an intermediary information layer that bridges legacy and modern decoders. Legacy decoders ignore these parameters and function as before, while modern decoders utilize them to achieve enhanced dynamic range control, allowing both to coexist without conflict
Solution Approach 2:
The bitstream format is designed to be universal, carrying DRC parameters that can be utilized by advanced decoders while remaining transparent to legacy decoders. This multi-functionality allows the same encoded content to serve both old and new playback equipment effectively
3Ease of operation
If simple DRC implementation is used to improve ease of operation, then ease of operation is improved, but dynamic range control precision is reduced
Solution Approach 1:
Instead of implementing complex algorithms, the system changes the approach by embedding pre-calculated DRC parameters directly in the bitstream. This transforms a potentially complex runtime calculation problem into a simple parameter application problem, maintaining ease of operation while achieving precise dynamic range control through the embedded guidance information
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.