Parametric Audio DRC Reversal for Consistent 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 coding format that includes pre-processing and post-processing dynamic range control (DRC) parameters to ensure consistent dialogue levels, allowing for seamless bitrate transitions by canceling or adjusting dynamic range limitations in both encoding and decoding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If adaptive bitrate coding is implemented to improve bandwidth efficiency, then network resource utilization is improved, but dynamic range inconsistencies occur during bitrate switching
Solution Approach 1:
The encoder pre-calculates and embeds DRC parameters in the bitstream that represent the dynamic range characteristics of the encoded audio signal. These parameters are prepared in advance so that the decoder can immediately apply the correct dynamic range adjustment when switching between bitrate modes, preventing dynamic range inconsistencies without requiring real-time analysis
Solution Approach 2:
DRC parameters serve as an intermediary between the encoded audio signal and the playback equipment. These parameters mediate the dynamic range characteristics, allowing the decoder to adjust the output dynamic range based on the encoded signal's properties and the playback equipment's capabilities, ensuring consistency across different bitrate modes
2Ease of operation
If legacy decoder compatibility is maintained to ensure backward compatibility, then ease of operation is improved, but dynamic range control precision deteriorates
Solution Approach 1:
The DRC parameter structure is designed to be universal, working with both legacy decoders that ignore the parameters and modern decoders that utilize them. The same bitstream format and parameter structure serve dual purposes: maintaining compatibility with old equipment while enabling precise dynamic range control on new equipment through the embedded DRC parameters
3Ease of manufacture
If simple DRC implementation is used to reduce device complexity, then ease of manufacture is improved, but dynamic range adaptability deteriorates
Solution Approach 1:
The system achieves enhanced dynamic range adaptability by changing and transmitting multiple DRC parameters (including compression ratio, knee level, and output level parameters) in the bitstream. These parameter changes allow the decoder to adapt its dynamic range processing to match both the encoded signal characteristics and the playback equipment capabilities, going beyond simple gain adjustment
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.