Decoder Aliasing Cancellation for Lossy-Lossless Audio Transitions
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Solution Overview
Problem
Conventional methods for switching between lossy and lossless audio streams face challenges in handling network bandwidth constraints and seamless transitions, particularly due to the lack of available side information for aliasing cancellation components, which affects audio playback quality.
Innovation Solution
A decoder generates aliasing cancellation components based on previously-decoded frames of the lossless stream, adding them to lossy time segments and normalizing the sum using an encoding window, allowing for seamless switching between lossy and lossless audio streams without requiring additional side information from the encoder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If aliasing cancellation components are not transmitted over the network, then network bandwidth is conserved and bit rate is reduced, but audio playback quality deteriorates due to aliasing artifacts during lossy/lossless transitions
Solution Approach 1:
The decoder generates the aliasing cancellation components itself using previously decoded lossless frames as a reference signal, rather than receiving them from the encoder. This self-service approach eliminates the need to transmit additional side information, conserving network bandwidth while maintaining audio quality through locally synthesized cancellation terms.
Solution Approach 2:
The decoder prepares aliasing cancellation components in advance by using previously decoded lossless frames before the actual lossy/lossless transition occurs. This preliminary generation of cancellation terms ensures that when the transition happens, the necessary components are already available, preventing aliasing artifacts without requiring real-time transmission of additional data.
2Manufacturing precision
If aliasing cancellation components are generated and added at the transition frame, then audio playback quality is maintained during switching, but decoder complexity increases
Solution Approach 1:
The decoder performs self-service by generating aliasing cancellation components from its own previously decoded lossless frames, eliminating the need for complex encoder-decoder coordination and side information transmission. This approach maintains audio quality while keeping the system relatively simple by utilizing resources already available at the decoder.
Solution Approach 2:
Previously decoded lossless frames serve as an intermediary reference signal that enables the generation of aliasing cancellation components. This intermediary approach allows the decoder to create the necessary cancellation terms without direct communication with the encoder, simplifying the overall system architecture while maintaining audio quality during transitions.
3Productivity
If lossy coded time segments are used under network bandwidth constraints, then network efficiency is improved, but audio quality deteriorates due to lossy compression artifacts
Solution Approach 1:
The patent converts the harmful aliasing artifacts that normally occur during lossy/lossless transitions into a beneficial effect by generating cancellation components that actively remove these artifacts. The lossy compression, which would normally degrade quality, is compensated for by adding the synthesized aliasing cancellation terms, thereby converting the harmful quantization effects into an opportunity for quality preservation.
Solution Approach 2:
Aliasing cancellation components act as an intermediary element that bridges the quality gap between lossy and lossless audio segments. By introducing these cancellation terms generated from previously decoded lossless frames, the system mediates the transition between compression modes while maintaining audio quality, allowing network efficiency to improve without sacrificing playback quality.
Data Source
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AI summary
Systems and methods are described for switching between lossy coded time segments and a lossless stream of the same source audio. A decoder may receive lossy coded time segments that include audio encoded using frequency-domain lossy coding. The decoder may also receive a lossless stream, which the decoder plays back, that includes audio from the same source encoded using lossless coding. In response to receiving a determination that network bandwidth is constrained, the decoder may generate an aliasing cancellation component based on a previously-decoded frame of the lossless stream, which may be added to a lossy time segment at a transition frame. The sum of the aliasing cancellation component and the lossy time segment may be normalized using a weight caused by an encoding window. Audio playback of the lossy coded time segments may then be provided, beginning with the aliasing-canceled transition frame.