QMF Audio Decoding Time Alignment for Waveform and Metadata
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Solution Overview
Problem
Existing audio encoding and decoding systems face challenges in providing low delay and efficient splicing of encoded bitstreams for real-time applications like live broadcasting, while maintaining latency and computational efficiency.
Innovation Solution
An audio decoder and encoder system that time-aligns waveform and metadata within access units using delay units to ensure precise alignment, allowing for splicing without re-sampling and maintaining high audio quality and low overall delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If waveform data and metadata are processed through different processing paths with different delays, then processing can be optimized for each path, but time misalignment occurs between waveform subband signals and decoded metadata
Solution Approach 1:
A delay unit is introduced as an intermediary component in the waveform processing path to compensate for the delay difference between waveform data and metadata processing paths. The delay unit delays the waveform subband signals by a predetermined number of time slots so that they arrive at the metadata application unit simultaneously with the decoded metadata, enabling both paths to operate independently for optimization while maintaining precise time alignment through the mediating delay component
2Manufacturing precision
If delay units are added to time-align waveform and metadata, then alignment precision is improved, but device complexity increases
Solution Approach 1:
Rather than adding complex synchronization mechanisms throughout the entire system, the delay unit is strategically placed at a specific location in the waveform processing path where it can locally compensate for the delay difference. This localized approach achieves precise time alignment without requiring system-wide complexity increases, as the delay unit operates independently at the point where alignment is needed
3Manufacturing precision
If waveform data is delayed to match metadata timing, then time alignment is achieved, but processing delay increases
Solution Approach 1:
The delay unit is configured to delay waveform subband signals by a predetermined number of time slots that corresponds to the delay difference between processing paths. This preliminary delay is calculated and applied in advance, allowing the waveform data to be synchronized with metadata without requiring additional delay compensation later in the processing chain, thereby minimizing the overall processing delay while achieving precise alignment
Data Source
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AI summary
The present document relates to time-alignment of encoded data of an audio encoder with associated metadata, such as spectral band replication (SBR) metadata. An audio decoder (100, 300) configured to determine a reconstructed frame of an audio signal (237) from an access unit (110) of a received data stream is described. The access unit (110) comprises waveform data (111) and metadata (112), wherein the waveform data (111) and the metadata (112) are associated with the same reconstructed frame of the audio signal (127). The audio decoder (100, 300) comprises a waveform processing path (101, 102, 103, 104, 105) configured to generate a plurality of waveform subband signals (123) from the waveform data (111), and a metadata processing path (108, 109) configured to generate decoded metadata (128) from the metadata (111).