Audio Stream Splicing Using Truncation Packets for Fine Timing
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Solution Overview
Problem
Existing audio splicing technologies are limited by the inability to address audio data at a finer granularity than the frame level, particularly in stream formats like MPEG-2 transport streams, and truncation information in codecs like AAC is deeply embedded and not easily modifiable for seamless splicing.
Innovation Solution
The introduction of truncation unit packets in audio data streams to indicate end portions of audio frames for discard during playback, allowing for precise splicing at access unit level without additional bitrate consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If audio data is addressed at frame level granularity (1024, 2048 or 4096 samples), then the audio stream can be processed using standard codecs like AAC or MPEG-H 3D Audio, but the temporal resolution for splicing operations is too coarse to achieve seamless transitions
Solution Approach 1:
The audio frame is segmented into multiple access units, each containing a subset of the frame samples. This segmentation enables splicing operations to occur at the access unit level (finer granularity) rather than requiring frame-level operations, thus improving temporal resolution while maintaining manageable complexity through standardized processing blocks
Solution Approach 2:
Truncation information is inserted into the coded audio data stream in advance, before splicing operations are performed. This preliminary marking of discardable samples allows splicing devices to easily identify and execute truncation at access unit boundaries without complex real-time analysis, reducing splicing operation complexity
2Productivity
If truncation information is deeply embedded in the AAC access unit structure, then the audio encoding can be efficient, but stream splicing devices cannot easily modify the truncation information on the fly
Solution Approach 1:
An intermediary truncation information structure is introduced that serves dual purposes: it is integrated into the AAC access unit for efficient encoding/decoding, while simultaneously providing accessible markers for splicing operations. This intermediary structure acts as a bridge between the encoding efficiency requirements and the splicing modifiability requirements
Solution Approach 2:
The truncation information structure is designed to serve multiple functions simultaneously: it enables efficient audio decoding in standard AAC players while also providing easily modifiable markers for stream splicing devices. This multi-functionality resolves the contradiction by making the same structure serve both encoding efficiency and splicing ease requirements
3Adaptability or versatility
If edit lists are used for discarding audio samples, then truncation can be achieved in MPEG-4 files, but the method is file format specific and cannot work with stream formats like MPEG-2 transport streams
Solution Approach 1:
The truncation information mechanism is designed to be universal across different audio file formats and stream formats. By implementing a format-agnostic approach that works with AAC, MPEG-H 3D Audio, and MPEG-2 transport streams, the solution achieves broad adaptability without requiring format-specific implementations, thereby reducing device complexity through standardization
Data Source
AI summary
Audio splicing is rendered more effective by the use of one or more truncation unit packets inserted into the audio data stream so as to indicate to an audio decoder, for a predetermined access unit, an end portion of an audio frame with which the predetermined access unit is associated, as to be discarded in playout.