Compressed Audio Cross-Fading via Single Decode
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Solution Overview
Problem
Existing digital media delivery systems struggle to implement efficient cross-fading and other effects between compressed audio streams on downstream devices, particularly due to limitations in simultaneous decoding and processing capabilities of consumer devices.
Innovation Solution
The system enables efficient cross-fading of compressed domain information streams by creating composite compressed packets from time-aligned packets of different streams, allowing for single decode operation and supporting various compression formats like AAC, Enhanced AAC Plus, and MP3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cross-fading is performed in real-time on consumer devices, then user experience is improved, but device complexity and processing requirements increase beyond current consumer device capabilities
Solution Approach 1:
The system performs preliminary actions by pre-processing and preparing media elements for cross-fading before delivery to the consumer device. The server prepares synchronized media streams with embedded timing information, so that the consumer device only needs to perform simple switching and fading operations rather than complex real-time decoding and synchronization.
Solution Approach 2:
The patent introduces an intermediary system (server-side processing) that handles the complex decoding and synchronization tasks. The server acts as a mediator between the media source and the consumer device, preparing the media streams in advance so that the consumer device can perform simple cross-fading operations without requiring advanced processing capabilities.
2Reliability
If dual decoding is implemented for cross-fading, then cross-fade quality is improved, but battery life is significantly reduced
Solution Approach 1:
The patent extracts the complex dual decoding operation from the consumer device and relocates it to the server-side processing system. The consumer device receives pre-decoded or pre-processed media streams that require minimal local processing, thereby eliminating the need for energy-intensive dual decoding on battery-powered devices while maintaining cross-fade quality.
3Measurement precision
If precise synchronization of multiple decoders is achieved, then cross-fading accuracy is improved, but device complexity and processing overhead increase
Solution Approach 1:
The system implements self-service synchronization by embedding timing and synchronization metadata directly into the media streams during server-side processing. The consumer device automatically synchronizes the media streams using the embedded timing information without requiring complex synchronization mechanisms or multiple coordinated decoders.
Data Source
AI summary
Systems and methods are presented for efficient cross-fading of compressed domain information streams on a user/client device. Exemplary systems may provide cross-fade between AAC/Enhanced AAC Plus information streams, between MP3 information streams, or between information streams of unmatched formats. These systems are distinguished in that cross-fade is directly applied to compressed bitstreams so a single decode operation is performed on the resulting bitstream. Thus, a set of frames from each input stream associated with the time interval in which a cross fade is decoded, and combined and recoded with a cross fade or other effect now in the compressed bitstream. Once sent through the client device's decoder, the user hears the transitional effect. The only input data that is decoded and processed is that associated with the portion of each stream used the crossfade, blend or other interstitial, and thus the vast majority of input streams are left compressed.