Microsoft’s Real-time audio (MS-RTA) codec was introduced in 2006. MS-RTA is Microsoft’s proprietary audio codec and is subject to terms and conditions of Microsoft License agreement. It operates on 16-bit speech signals sampled at 8 KHz or 16 KHz and generates a compressed bit-stream having average bit-rates of 8.8 or 18 kbps respectively. It is a sub-band coder and has a look ahead delay of 10ms. The encoder optionally includes forward error correction (FEC) block to embed error recovery data in the bit-stream. The decoder has an optional jitter-control module that provides active management of jitter control and packet loss concealment. It is the default codec for Microsoft’s Unified Communications Platforms, and is designed for real-time, two way VoIP applications.
- Based on Microsoft Standard specification
- Optimized ASM/C implementation
- Re-entrant implementation
- C-callable APIs
- Support for 8.8 kbps and 18 kbps average bit-rates.
- Support for variable and fixed rate decoding.
- Supports integrated Packet Loss Concealment (PLC) algorithm.
- Support for direct-mode and pull-mode operation.
- The implementation supports both Little-Endian and Big-Endian (on ARM and C64x+ platforms)
- Optional support for xDM APIs.
- Tested for bit-exactness with standard as well as a large database of non-standard test vectors
- Module is fully interruptible (Maximum interrupt latency on C64x+ is 6000 cycles).
- Tested for any illegal memory access by the module (C64x+ and ARM)
- Tested for compliance with register preservation requirements
- Tested for Input buffer corruption
- Tested for I/O buffer alignment requirements
- Tested for multi-instance implementation
- Tested for 100% code coverage
- Range validation for all the API parameters
- Tested with scratch contamination at frame boundaries
- Tested for packet loss conditions with 5% loss to 25% loss
- Tested pull-mode decoder by simulating a large set of jitter conditions.
- ARM implementation validated on OMAP3530 (Cortex-A8) and DM6446/DM6467 (ARM926EJ-S) platforms.
- TI C64x+ implementation validated on Spectrum Digital C6455 DSK, DM6446 EVM and OMAP3530 platform.
- TI C55x implementation validated on Spectrum Digital C5510 DSK
ARM9E, ARM11, Cortex-A8, Cortex-A9, TI C55x, and TI C64x+