Decoder Aliasing Cancellation for Lossy Lossless Audio Transitions
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Solution Overview
Problem
Existing systems face challenges in seamlessly switching between lossy and lossless audio streams due to network bandwidth constraints, as they require side information for aliasing cancellation, which is not always available and complicates efficient transitions between encoding modes.
Innovation Solution
A decoder generates an aliasing cancellation component based on previously-decoded frames of the lossless stream, which is added to the lossy time segment and normalized using an encoding window, allowing for seamless playback without requiring additional side information from the encoder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aliasing cancellation components are transmitted as side information from encoder to decoder, then switching between lossy and lossless modes is possible, but network bandwidth is consumed and system complexity increases
Solution Approach 1:
The decoder generates the aliasing cancellation components itself using previously decoded lossless frames and extrapolation, eliminating the need for the encoder to transmit these components as side information. This self-service approach resolves the contradiction by making the decoder independent of additional bandwidth for obtaining cancellation components.
Solution Approach 2:
The patent extracts the aliasing cancellation function from the encoder-side side information transmission and relocates it to the decoder-side generation process. By taking out the transmission requirement and performing the cancellation component generation locally at the decoder, the system maintains switching capability without consuming additional network bandwidth.
2Reliability
If aliasing cancellation components are transmitted as side information, then aliasing cancellation is achieved, but device complexity and processing overhead increase
Solution Approach 1:
The decoder performs self-service by generating aliasing cancellation components from its own previously decoded frames through extrapolation, eliminating the need for complex encoder-decoder coordination and side information processing. This reduces overall system complexity while maintaining aliasing cancellation effectiveness.
3Productivity
If lossy coded time segments are used under bandwidth constraints, then network efficiency is improved, but audio quality deteriorates due to aliasing
Solution Approach 1:
The patent converts the harmful aliasing effect introduced by lossy coding into a beneficial situation by generating cancellation components from the same lossy decoded frames. The extrapolation process uses the aliased signal itself to create the cancellation component, which is then added back to remove the aliasing, thus converting the harm into a benefit while maintaining network efficiency.
Data Source
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.