MDCT Audio Mixing Across Different Sample Rates Without Added Latency
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Solution Overview
Problem
Existing wireless communication systems face challenges in seamlessly mixing audio streams with different sample rates without introducing additional latency or reducing audio quality, particularly when switching between high-quality and low-latency audio streams.
Innovation Solution
Implementing modified discrete cosine transform (MDCT) for mixing audio streams in the frequency domain, allowing direct mixing of streams with different sample rates without converting them to a common rate, and using pre-emphasis filtering and dynamic adjustment of MDCT audio bandwidth to match link performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sample rate conversion is performed to mix audio streams with different sample rates, then mixing compatibility is improved, but additional latency is introduced
Solution Approach 1:
The patent extracts the sample rate conversion operation from the audio mixing process. Instead of converting all streams to a common sample rate before mixing, the system processes each stream at its native sample rate through separate MDCT filters, eliminating the need for traditional sample rate conversion while maintaining mixing compatibility across different sample rates.
Solution Approach 2:
The patent introduces MDCT frequency domain representation as an intermediary. Audio streams with different sample rates are independently transformed into the MDCT domain, where they can be mixed without requiring sample rate conversion. This intermediary transformation enables direct mixing while preserving the original sample rates, thus avoiding the latency associated with traditional conversion methods.
2Ease of manufacture
If audio streams are mixed in the time domain using traditional methods, then processing simplicity is maintained, but audio quality degrades due to sample rate conversion artifacts
Solution Approach 1:
The patent replaces the traditional time-domain mixing mechanism with a frequency-domain MDCT-based mechanism. Instead of converting sample rates and mixing in the time domain, the system transforms audio streams into the MDCT frequency domain, applies independent filtering to each stream, and mixes them in the frequency domain. This substitution eliminates conversion artifacts while maintaining processing efficiency through vectorized operations.
3Ease of manufacture
If fixed MDCT audio bandwidth is used, then implementation simplicity is improved, but adaptability to different link performances deteriorates
Solution Approach 1:
The patent implements dynamic MDCT audio bandwidth adjustment that adapts to different link performances. The system can modify the audio bandwidth parameter based on channel conditions, allowing high-bandwidth links to transmit high-quality audio while automatically reducing bandwidth for constrained links. This dynamic adjustment maintains implementation simplicity through parameter configuration while achieving adaptability to varying link capabilities.
Data Source
AI summary
This disclosure provides methods, components, devices and systems for multi-rate audio mixing. Some aspects more specifically relate to mixing audio streams with different sample rates. In some examples, an audio source device may convert audio streams with different sample rates to the frequency domain using a modified discrete cosine transform (MDCT), and the audio source device may mix the audio streams with different sample rates in the frequency domain. The audio source device may apply a pre-emphasis filter after mixing the audio streams in the frequency domain. An audio stream with a higher sample rate may be down-sampled by dropping frequency bins after converting the audio stream to the frequency domain. Additionally, or alternatively, an audio stream with a lower sample rate may be up-sampled by padding frequency bins of the frequency domain-converted audio stream.