GSM Enhanced Full Rate (EFR) Codec

GSM Enhanced Full Rate (EFR) codec is available as a real-time implementation that can be configured to support multi-channel applications. GSM EFR software may be licensed standalone , as part of a modular software library suite, as well as with a VoIP stack for different  integration options with developer applications.  Contact us to discuss your voice application requirements.

VOCAL’s GSM EFR speech compression source code is optimized to run on leading DSPs and conventional processors from TI, ADI, AMD, Intel and other vendors. GSM EFR codec is also available as a custom design to meet your specific needs.

GSM EFR

GSM EFR specification describes the detailed mapping between input blocks of 160 speech samples in 13-bit uniform PCM form to encoded blocks of 244 bits and from encoded blocks of 244 bits to output blocks of 160 reconstructed speech samples. The sampling rate is 8,000 sample/s leading to a bit rate for the encoded bit stream of 12,2 kbit/s. The coding scheme is the so-called Algebraic Code Excited Linear Prediction Coder (ACELP).

GSM EFR 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. This part also describes the codec down to the bit level, thus enabling the verification of compliance to the part to a high degree of confidence by use of a set of digital test sequences.

Configurations

• DAA interface using linear codec at 8.0 kHz sample rate
• Direct interface to 8.0 kHz PCM data stream (A-law or μ-law)
• North American/International Telephony (including caller ID) support available
• Simultaneous DTMF detector operation available – (less than 10 talkoff hits on Bellcore test tape set)
• MF tone detectors, general purpose programmable tone detectors/generators available
• Data/Facsimile/Voice Distinction available
• Common compressed speech frame stream interface to support systems with multiple speech coders
• Dynamic speech coders selection if multiple speech codecs available
• Can be integrated with Acoustic Echo Canceller, G.168 Line Echo Canceller and Tone Detection/Regeneration modules
• Can be integrated with VoIP stack