MCSTF optimization

[GUNASRIJ11]

Summary

Adds multi-threaded execution and AVX2 SIMD kernels to Motion-Compensated Spatio-Temporal Filtering (MCSTF), decouples it from the badapt (B-adaptive) flow so it can run independently, and adds a noise-based selective mode plus test bench coverage.

Key changes

Multi-threading

• Implemented multithreaded motion estimation for MCSTF to process ME rows in parallel.
• Implemented a multi-threaded workflow for bilateralFilter
• Added CLI --mcstf-ref-range to control param->mcstfFrameRange

AVX2 SIMD kernels

• motionErrorLumaFrac (2.81x) , applyMotion (4.44x) , computeBlockStats (4.19x) and bilateralFilter (1.38x)

Algorithm/pipeline changes

• Generate lowres planes using HM-equivalent averaging
• Pruned unused computations in the MCSTF path
• Decoupled MCSTF's HME (hierarchical motion estimation) from the b-adapt flow so MCSTF no longer depends on B-adaptive lookahead state

Selective MCSTF (noise-based)

• Added --selective-mcstf CLI option to enable noise-based MCSTF filtering — skips filtering on frames whose estimated noise is low, saving cycles.

Testing

• Added test bench support for MCSTF
• Enabled profiling stats for MCSTF