G.711 PCM Codec
G.711 PCM is an internet wideband audio codec used in VoIP applications

G 711 Codecs and G 711a codecs

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G.711 Pulse Code Modulation聽(PCM) is a commonly used waveform for speech encoding and is suitable for use as an internet wideband audio codec in VoIP applications.聽Contact us聽to discuss your G.711 vocoder requirements.

VOCAL’s G 711 codec source code is optimized for leading DSPs and RISC/CISC processors from TI, ADI, ARM, Intel and other vendors. Custom designs are available to meet specific voice codec requirements. The G.711 codec may be licensed as a standalone voice compression algorithm, a library, or with a VoIP stack.

G.711 PCM

The G.711 PCM codec algorithm uses a sampling rate of 8,000 samples per second, with a tolerance on that rate of 50 parts per million聽(ppm). Non-uniform quantization with 8 bits is used to represent each sample, resulting in a 64 kbps bit rate.

There are two slightly different聽G.711 PCM聽versions; 渭-law, which is used primarily in North America, and A-law, which聽is used by most other countries in the rest of the world. While 渭-law tends to give more resolution to聽higher range signals, G.711 A-law provides more quantization levels at lower signal levels.

When using G.711 渭-law in networks where suppression of the all 0 character signal is required, the聽character signal corresponding to negative input values between decision value numbers 127 and 128 should be聽00000010 and the value at the decoder output is -7519. The corresponding G.711 decoder output value number is 125.

G.711 Appendix I

ITU G.711 Appendix I outlines a聽Packet Loss Concealment (PLC) algorithm, also known as a frame erasure concealment algorithm. PLC can help hide聽transmission losses in a packetized network, specifically, in an audio system where the input signal is encoded聽and packetized at a transmitter first before being sent over a network where it is received at an end point, decoded and output as audio. Like G.711, many of the standard CELP-based speech coders, such as聽G.723.1, G.728 and G.729, also have PLC algorithms built into their standards.

G.711 Appendix II

ITU G.711 Appendix II defines a standard method to perform Discontinuous Transmission (DTX) in a packet-based multimedia communication聽system. 聽DTX utilizes the聽fact that a significant amount of voice traffic may not contain any speech but only background noise. This聽can be detected using聽Voice Activity Detection聽(VAD)聽and therefore fewer, smaller packets may be transmitted. Since audio is no longer聽transmitted in a continuous stream,聽Comfort Noise Generation聽(CNG) mimics the background silence.



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supported platforms

VOCAL鈥檚 optimized vocoder software is available for the following platforms.聽Please contact us for specific G.711 codec supported platforms.

ProcessorsOperating Systems
路聽聽聽聽聽聽聽 Texas Instruments – C6000 (TMS320C62x, TMS320C64x, TMS320C645x, TMS320C66x, TMS320C67x), DaVinci, OMAP, C5000 (TMS320C55x)

路聽聽聽聽聽聽聽 Analog Devices – Blackfin, TigerSHARC, SHARC

路聽聽聽聽聽聽聽 PowerPC

路聽聽聽聽聽聽聽 MIPS – MIPS32, MIPS64, MIPS4Kc

路聽聽聽聽聽聽聽 ARM 鈥 ARM7, ARM9, ARM9E, ARM10E, ARM11, StrongARM, ARMCortex-A8/A9/A15/A3x/A5x/A7x, Cortex-M3/M4/M7/M33

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

路聽聽聽聽聽聽聽 Google Android

路聽聽聽聽聽聽聽 Apple iOS / iPhone / iPad & MacOS

路聽聽聽聽聽聽聽 Unix,聽聽Linux, 渭Clinux, BSD

路聽聽聽聽聽聽聽 Microsoft Windows ACM / RTC / CE / Mobile

路聽聽聽聽聽聽聽 Symbian

路聽聽聽聽聽聽聽 eCOS / eCOSPro

路聽聽聽聽聽聽聽 Wind River VxWorks

路聽聽聽聽聽聽聽 Green Hills聽Integrity

路聽聽聽聽聽聽聽 VOCAL LANsEND

路聽聽聽聽聽聽聽 Micrium 渭COS