MELPe TSVCIS Vocoder Software

Tactical Secure Voice Cryptographic Interoperability Specification (TSVCIS) introduces the Wideband Waveform, which provides the framework for improved speech intelligibility, security, and robustness of defense radio communications. In the Wideband Waveform of TSVCIS the bit rates of MELPe have been extended to include data rates of 8000, 12000 and 16000 bps. This allows for the radio users to selectively determine the characteristics of the radio communication. If the radio communication is noisy, a lower MELPe rate can be selected and the number of parity bits used for the FEC can be increased. On the other hand, a higher MELPe bit rate can be selected to improve the intelligibility of the speech, if the channel’s error rate is low. TSVCIS was designed to be inter-operable to with SCIP, so the MELPe bit rate extensions were designed to easily switch back to using standard Narrowband MELPe.

TSVCIS Vocoder

VOCAL’s enhanced Mixed-Excitation Linear Predictive (MELPe) vocoder is ideal for a range of low power and low bandwidth applications including PDAs, mobile devices and cell phones, VoIP, secure voice and radio, ground mobile and software defined radios as well as the Joint Tactical Radio System (JTRS), JTRS Handheld, Manpack and Small Form Fit (HMS) and Soldier Radio Waveform (SRW). It is commonly known in the U.S. as MIL-STD-3005 and in NATO as STANAG 4591. 

The use of TSVCIS with RTP and SDP is described in detail in RFC8817 – RTP Payload Format for Tactical Secure Voice Cryptographic Interoperability Specification (TSVCIS) Codec

Our MELPe TSVCIS voice compression algorithm is available either standalone, as an embedded software library, with a VoIP stack or as part of a complete design. MELPe may be licensed for a flat fee. VOCAL does not charge a royalty; nor is there any fee due to Compandent.


  • Based on Naval Research Lab’s (NRL’s) Variable Data Rate (VDR) Speech Codec
  • Wideband Voice 16 without FEC (TSVCIS Appendix E)
  • Wideband Voice 16 with in-band FEC (TSVCIS Appendix F)
  • Wideband Voice 16 Gateway – Narrowband – Wideband Crossbanding (TSVCIS Appendix G)
  • Wideband Voice 12 with in-band FEC (TSVCIS Appendix H)
  • Wideband Voice 8 with in-band FEC (TSVCIS Appendix I)
  • Optional BCH and Hamming libraries
  • Scalable narrowband voice codec augmenting the MELPe encoded parameters
  • Includes MELPe 2400, 1200, and 600 bps rates
  • Uses a variable number of LSF parameters packed into octets (up to tcmax)
  • Gateways/receivers may pass/use fewer LSF octets
  • C Callable Interface
  • RFC8817 RTP Payload format support available


VOCAL’s optimized vocoder software is available for the following platforms. VOCAL has updated its MELPe offering to include TSVCIS MELPe variations.  In addition, VOCAL also offers FEC software to complement our TSVCIS MELPe.  Please contact us for specific TSVCIS codec supported platforms and performance information.


Operating Systems

·        Texas Instruments – C6000 (TMS320C62x, TMS320C64x, TMS320C645x, TMS320C66x, TMS320C67x), DaVinci, OMAP, C5000 (TMS320C55x)

·        Analog Devices – Blackfin, TigerSHARC, SHARC

·        PowerPC

·        MIPS – MIPS32, MIPS64, MIPS4Kc

·        ARM – ARM7, ARM9, ARM9E, ARM10E, ARM11, StrongARM, Cortex-A8/A9, Cortex-A53,Cortex-M3/M4/M7

·        Intel / AMD – x86, x64 (both 32 and 64 bit modes)

·        Google Android

·        Apple iOS / iPhone / iPad & MacOS

·        Unix,  Linux, μClinux, BSD

·        Microsoft Windows ACM / RTC / CE / Mobile

·        Symbian

·        eCOS / eCOSPro

·        Wind River VxWorks

·        Green Hills Integrity

·        VOCAL LANsEND

·        Micrium μCOS