Wideband versus Narrowband VoIP Codecs – What is Right for You?

This article takes you through the decision of choosing wideband over narrowband voice and also choosing the right codec to trade-off the best functionalities in your VoIP system.

When speaking of Voice over IP applications, there is no doubt that wideband voice offers a clear benefit to users. In the case of standard narrowband VoIP calls, the voice signal is typically sampled only at 8000 Hz providing an effective voice pass-band that ranges between 200 and 3300 Hz. On the other hand, go through G.722 codec specifications and other wideband codecs and you will note that it offers as much as twice the sample rate with an effective pass-band of 50 to 7000 Hz.

How Does This Translate Into a Benefit For The End User?

The increase in sample rate typically provides end users with an impressively higher fidelity voice call that sounds almost like you are speaking with someone in the same room and not over a phone or video conferencing system.

Why Don’t All VoIP Devices Switch To Wideband Voice?

While the clarity of voice is significantly higher in case of a wideband codec, there is also the trade-off in the processing horsepower as well as the bandwidth it requires to be taken into account.

Even though there are a host of codecs you will find, the most commonly used one is the G.722, a split-band variant of the ADPCM waveform codec. This codec was standardized by the International Telecommunications Union (ITU) about 27 years ago and do not consume too many CPU cycles for the purpose of voice processing. However, they require relatively more bandwidth for their voice channels.

When speaking specifically of the G.722, you will find that it requires almost the same digital signal processing (DSP) horsepower as the G.726 (narrowband ADPCM). That said, the former requires a data rate of 48 to 64 kbps. This is because it has a larger sample rate of the voice channel. In comparison to this, narrowband codecs such as the G.711 only require about 32 kbps or sometimes even lower than that.

Solving the Bandwidth Problem

In 2002, the ITU introduced the G.722.2 codec that intended to take care of the extra bandwidth its predecessor required. With the help of wideband voice, this codec was able to leverage the Wideband-Adaptive Multi-Rate (WB-AMR) compression codec. This 2002 version of the codec was successful in shrinking the bit rate of the voice channel to a mere 12.65 kbps from the former 48 kbps and also offering enhanced quality. Many IP phone manufacturers looking for a better quality wideband voice that requires a small bandwidth jumped on to the G.722.2 bandwagon.

However, the upgrade comes with a cost since its need for CPU processing horsepower goes up. The 2002 upgrade requires about four to five times more CPU cycles when compared to the older G.722 codec.

After going through the G722 codec specifications, you will be able to make the right trade-off depending on the features you need to incorporate in your VoIP system. Choosing wideband voice over narrowband, in general, is an excellent way to ensure quality.

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If you want to know about G729 codec specification, the author of this article recommends CodecPro.