Audio Codec Transient Coding to Reduce Pre-Echo Artifacts

The audio signal is divided into multiple blocks for MDCT processing, and the patent identifies specific blocks containing transient signals. By segmenting the processing approach - using different block sizes (short blocks for transients, long blocks for steady-state signals) and different coding modes (transform coding vs. adaptive differential pulse code modulation), the patent prevents error spreading across entire long blocks, thereby reducing pre-echo artifacts while maintaining compression efficiency.

The patent dynamically adjusts the coding approach based on signal characteristics. It detects transient signals and adapts the block size and coding mode accordingly - using short blocks and adaptive differential pulse code modulation for transient regions, and long blocks with transform coding for steady-state regions. This dynamic adaptation allows the system to maintain high compression efficiency while minimizing pre-echo artifacts in transient regions.

The patent applies different quantization strategies to different signal regions. In transient regions identified by signal detection, it uses adaptive differential pulse code modulation with higher precision to minimize quantization errors that would cause pre-echo. In steady-state regions, it can use more aggressive quantization for better compression. This localized quality adjustment allows bit rate reduction overall while protecting transient regions from excessive quantization artifacts.

The patent performs preliminary detection of transient signals before applying quantization and coding. By identifying transient regions in advance, it can prepare appropriate coding parameters (shorter blocks, different quantization schemes) to prevent pre-echo artifacts before they occur, rather than attempting to correct them after quantization has been applied uniformly.

The patent implements dynamic block size selection based on signal analysis. It detects transient signals and automatically switches between short and long block sizes, as well as between different coding modes (transform coding and adaptive differential pulse code modulation). This dynamic approach effectively controls pre-echo in transient signals while the automation keeps processing complexity manageable.

The system performs self-adaptation by automatically detecting signal characteristics and selecting appropriate coding parameters without external intervention. The transient detection and block size selection are automated processes that make the system self-adjusting, reducing the need for complex manual configuration while achieving effective pre-echo control.

The patent implements dynamic adaptation to network conditions by adjusting audio coding parameters based on available bandwidth and quality requirements. It can switch between different coding modes and bit rates to adapt to varying network conditions in distributed IP-based systems, making the system versatile for different network environments while maintaining reasonable implementation complexity through automated control.

The patent creates a multi-functional coding system that can operate in multiple modes (transform coding, adaptive differential pulse code modulation, different block sizes) to serve various network conditions and quality requirements. This universal approach allows a single system to adapt to both traditional broadcast and distributed IP-based networks, enhancing versatility without requiring entirely separate systems.