Complete Communications Engineering

VOCAL offers the GSM Full Rate (FR) codec as a real-time implementation that can be configured to support multichannel applications. GSM FR software is available for licensing as a standalone algorithm, as a library, and with a VoIP stack . Contact us to discuss your GSM FR vocoder application requirements.

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The GSM FR speech compression source code is optimized to run on DSPs and conventional processors from TI, ADI, ARM, AMD, Intel and other leading vendors. Custom designs are also available for our clients.


GSM FR defines a reference configuration for the speech transmission chain of the digital cellular telecommunications system. The speech encoder takes its input as a 13 bit uniform PCM signal either from the audio part of the mobile station or on the network side, from the PSTN via an 8 bit/A-law to 13 bit uniform PCM conversion. The encoded speech at the output of the speech encoder is delivered to a channel encoder unit which is specified in GSM 05.03. In the receive direction, the inverse operations take place.

GSM FR describes the detailed mapping between input blocks of 160 speech samples in 13 bit uniform PCM form to encoded blocks of 260 bits and from encoded blocks of 260 bits to output blocks of 160 reconstructed speech samples. The sampling rate is 8,000 sample/s leading to an average bit rate for the encoded bit stream of 13 kbit/s. The coding scheme is the so-called Regular Pulse Excitation – Long Term prediction – Linear Predictive Coder, hereinafter referred to as RPE-LTP.

GSM FR also specifies the conversion between A-law PCM and 13 bit uniform PCM. Performance requirements for the audio input and output parts are included only to the extent that they affect the transcoder performance. It also describes the codec down to the bit level, thus enabling the verification of compliance to the recommendation to a high degree of confidence by use of a set of digital test sequences.



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VOCAL’s optimized vocoder software is available for the following platforms. Please contact us for specific vocoder supported platforms and performance information.

ProcessorsOperating Systems
  • Texas Instruments – C6xx (TMS320C62x, TMS320C64x, TMS320C645x, TMS320C66x, TMS320C67x), DaVinci, OMAP, C5xx (TMS320C54x, TMS320C55x)
  • Analog Devices – Blackfin, ADSP-21xx, TigerSHARC, SHARC
  • PowerPC, PowerQUICC
  • MIPS – MIPS32, MIPS64, MIPS4Kc
  • ARM – ARM7, ARM9, ARM9E, ARM10E, ARM11, StrongARM, ARMCortex-A8/A9/A15/A3x/A5x/A7x, Cortex-M3/M4/M7/M33
  • Intel / AMD – x86, x64 (both 32 and 64 bit modes)
  • Linux, uClinux, BSD, Unix
  • Microsoft Windows ACM / RTC / CE / Mobile
  • Apple iOS / iPhone / iPad & MacOS
  • Google Android
  • Green Hills Integrity
  • Micrium μCOS
  • Symbian
  • Wind River VxWorks
  • eCOS / eCOSPro