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The pinnacle of narrowband audio: Why does G.711 provide high-quality voice?
Since 1972, G.711 encoding has become the standard in the field of voice communications. As a narrow-band audio codec, G.711 provides high-quality speech at a bit rate of 64 kbit/s, making it widely used in global communication networks. G.711 is designed to handle speech frequencies from 300 to 3400 Hz and samples at a frequency of 8000 times per second. All this not only gives G.711 excellent performance in voice calls, but is also the cornerstone of many network protocols.
G.711 uses two different logarithmic compression algorithms: μ-law (mainly used in North America and Japan), and A-law (used in most countries outside North America).
The use of these two algorithms gives G.711 flexibility and acceptable voice quality in different markets. μ-law generally provides better resolution in the high signal range, while A-law provides more quantization levels in the low signal range.
Standard specifications and characteristics of G.711
As one of the ITU-T standards, G.711 is not only used to transmit voice, but also supports fax communications and other applications. Its design fully considers the delay and reliability in the network environment, making it adaptable to many instant messaging needs. The main features of G.711 are as follows:
- Sampling frequency: 8 kHz
- Bit rate: 64 kbit/s
- Typical algorithm delay: 0.125 ms
In addition, G.711 also contains appendices that define how to hide audio loss (PLC) transmitted over packetized networks, and how to use voice activity detection (VAD) and comfort noise generation (CNG) to reduce silence Bandwidth usage during the period.
In PSQM testing under ideal conditions, both G.711 μ-law and G.711 A-law had an average opinion score of 4.45.
This result shows the consistent performance of G.711 in different markets and application environments, attracting countless enterprises to choose it as a voice communication solution.
Two main encoding algorithms of G.711
G.711 has two main logarithmic encoding algorithms - μ-law and A-law. Although both algorithms are logarithmic, they are fundamentally different from each other. A-law is designed to be simpler for computer processing, while μ-law will provide higher resolution to high-frequency audio.
In G.711, μ-law is generally encoded as a 14-bit signature linear audio sample, which is converted into an 8-bit value. These encoded samples will be inverted during transmission to increase the 0/1 transition and facilitate clock recovery.
These careful design choices ensure that G.711 can handle both voice clarity and network adaptability.
Extended version covering G.711
With the advancement of technology, G.711 is constantly being expanded to meet higher sound quality requirements. For example, G.711.0 is a technology that uses lossless data compression to reduce bandwidth usage by up to 50%. G.711.1 is a higher-fidelity extension with multi-layer enhancements that can provide 16-bit audio encoding and even "ultra-wideband" up to 16 kHz.
These extensions allow G.711 to maintain its core advantages while providing a variety of sound quality options to meet different application needs.
This series of improvements demonstrates why G.711 has continued to lead the field of audio coding since 1972, and its stable performance and low latency characteristics are even more indispensable.
The future of G.711
With the growing demand for high-quality audio and low-latency communications, will future network technology continue to revolve around G.711, allowing this ancient standard to shine in the new technological environment?
