Audio Transcoder Filter Bank Merging AAC AC-3
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Solution Overview
Problem
Existing audio transcoding methods are inefficient as they do not effectively exploit the information available from the decoder to simplify the encoder, leading to increased complexity and resource requirements in transcoding between different audio standards like AAC and AC-3.
Innovation Solution
The method involves determining if AAC joint stereo exists and using this information to optimize rematrixing and bit allocation processes, reducing the complexity of the AC-3 encoder by leveraging similarities in subband coding schemes and filter banks between AAC and AC-3 standards, thereby simplifying the transcoding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a tandem realization of independent audio decoder and encoder is used, then audio transcoding between different standards is achieved, but the complexity of the audio encoder increases and resource requirements increase
Solution Approach 1:
The patent merges the decoder and encoder into a unified transcoder architecture where the AC-3 encoder shares the analysis filter bank with the AAC decoder. This combining of components allows the system to achieve audio transcoding between AAC and AC-3 standards while reducing overall complexity by eliminating redundant filter bank implementations and enabling shared memory structures.
Solution Approach 2:
The analysis filter bank is designed to serve multiple functions: it operates as part of the AAC decoder during decoding operations and as part of the AC-3 encoder during transcoding operations. This multi-functional design reduces device complexity by eliminating the need for separate filter bank implementations for each audio standard.
2Adaptability or versatility
If a tandem realization of independent audio decoder and encoder is used, then audio transcoding between different standards is achieved, but RAM and ROM requirements increase
Solution Approach 1:
The patent merges the decoder and encoder into a unified transcoder architecture where the AC-3 encoder shares the analysis filter bank with the AAC decoder. This combining of components allows the system to achieve audio transcoding between AAC and AC-3 standards while reducing overall complexity by eliminating redundant filter bank implementations and enabling shared memory structures.
Solution Approach 2:
The analysis filter bank is designed to serve multiple functions: it operates as part of the AAC decoder during decoding operations and as part of the AC-3 encoder during transcoding operations. This multi-functional design reduces device complexity by eliminating the need for separate filter bank implementations for each audio standard.
3Reliability
If reference AC-3 rematrixing is always run, then audio quality is maintained, but reordering complexity increases
Solution Approach 1:
The patent implements dynamic rematrixing selection where the system determines whether AAC joint stereo exists and selectively applies rematrixing based on this condition. When AAC joint stereo is detected, the system enables rematrixing to maintain audio quality; when it is not detected, the system skips rematrixing to reduce complexity. This dynamic approach adapts the processing level to the actual audio content requirements.
Solution Approach 2:
The system changes the rematrixing parameter based on the detection of AAC joint stereo characteristics. By monitoring the presence of joint stereo encoding in the AAC data, the system adjusts whether to apply AC-3 rematrixing, thereby optimizing the balance between audio quality preservation and processing complexity reduction.
Data Source
AI summary
A method and apparatus for transcoding audio data. The method includes determining if AAC joint stereo exists, running a reference AC-3 rematrixing when the AAC joint stereo does not exist, when AAC joint stereo does exist, enabling rematrixing when the number of corresponding AAC bands is greater than half the size of the band, otherwise, running reference AC-3 rematrixing.