MPEG Surround Decoder Delay Compensation for HE-AAC Audio Sync
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Solution Overview
Problem
The synchronization of multi-channel audio signals between an MPEG surround decoder and a HE-AAC decoder is disrupted due to different delays between downmix signals in the time domain and QMF domain, causing desynchronization of spatial parameters.
Innovation Solution
Incorporating a real-to-complex converter and delay units to account for and apply delays in the QMF and Nyquist filter banks, ensuring synchronization by converting real QMF signals to complex QMF signals and adding necessary delays to spatial parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If downmix signals are processed through QMF and Nyquist filter banks in the MPEG surround decoder, then multi-channel audio signals can be restored, but delay occurs causing desynchronization between downmix signals and spatial parameters
Solution Approach 1:
The patent applies preliminary action by calculating the delay difference between time-domain and QMF-domain downmix signals in advance, then applying this delay compensation to spatial parameters before processing. This ensures that synchronization is maintained throughout the decoding process without causing desynchronization issues.
2Loss of time
If QMF domain signals are used directly from HE-AAC decoder to avoid filtering delay, then processing time is reduced, but delay differences between time domain and QMF domain signals cause desynchronization
Solution Approach 1:
The patent applies parameter changes by identifying and calculating the specific delay difference (e.g., 704 samples in analysis filter bank plus 257 samples in synthesis filter bank equals 961 samples) between time-domain and QMF-domain signals. This delay parameter is then used to compensate spatial parameters, ensuring synchronization while maintaining the efficiency benefits of using QMF domain signals directly.
3Reliability
If high-quality MPEG surround decoder uses both time domain and QMF domain downmix signals, then audio quality is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by separating the handling of time-domain and QMF-domain downmix signals into distinct processing paths. Each path is processed independently with appropriate delay compensation applied to spatial parameters, allowing the system to utilize both signal types for high audio quality while managing complexity through structured organization of processing stages.
Data Source
AI summary
Provided is a method for controlling synchronizing downmix signals and MPEG surround side information signals by controlling a delay according to the kind of downmix audio signals in an MPEG surround decoder. When multi-channel audio signals are restored using an HE-AAC decoder and a low-power MPEG surround decoder and complex QMF signals outputted from the HE-AAC decoder are used as downmix signals, a delay unit compensates for a delay caused in a real-to-complex converter. Anther delay unit delays spatial parameters to compensate for a delay caused in QMF and Nyquist banks when time-domain downmix signals are used. Also, when multi-channel audio signals are restored using an HE-AAC decoder and a high-quality MPEG surround decoder and complex QMF signals outputted from the HE-AAC decoder are used as downmix signals, a delay unit compensates for a delay caused in a real-to-complex converter.