VoLTE and EVS HD Codec – New Sound Quality. How to include what we get in practice


Cellular communication originally emerged as a method of voice communication, although today we are increasingly writing messages in instant messengers, dictating notes and relatively rarely making calls. Communication culture and etiquette have changed, although voice calls remain an important part of everyday communication. Before the advent of 3G networks, when making a voice call, the Internet connection was broken, your phone did not receive data in the background, unless you were connected to Wi-Fi. The 3G network settings were often such that the simultaneous operation of the Internet and voice did not work in practice.

For a society that is focused on the constant transfer of data, on simultaneous conversations and viewing the network, instant messengers, this was an unacceptable flaw in technology. Therefore, new opportunities were initially laid in 4G networks, the voice must be digital, transmitted as data, and at the same time the mobile Internet will work, it will not disappear. This approach was beneficial for everyone – operators received efficient use of frequencies, in digital it was possible to transmit more calls to one base station, for subscribers this meant better voice quality, the ability to use advanced codecs, and most importantly, their smartphones were always in touch … In fact, it was possible to do many different things at the same time – talking on the phone, using the speakerphone or headphones, viewing messages in mail or messenger, watching web resources, and much more. The advent of 4G networks has become a watershed moment for voice communications, it has become better and more convenient.

In LTE networks, there is such a service as VoLTE (Voice over LTE), this is just voice transmission over an LTE network. VoLTE support is included in most modern smartphones from both well-known manufacturers and second-tier companies. You can find VoLTE on smartphones from Apple, Samsung, Huawei, Honor, Sony and many others, there are more than a hundred different models. Surprisingly, many people simply do not realize or know that their device supports VoLTE and what benefits they get from using this technology. The key feature is the use of advanced codecs for sound, the interlocutor feels completely different than in the networks of previous generations, it seems that you can reach out and reach the person, touch him.

It’s hard for me to remember when I started using VoLTE on my main number, it seems like it was 2016. But every time, going to another country where the operator did not support this technology, I involuntarily frowned, plunged into the past. This difference was always very noticeable, it was impossible to ignore it. To make this text useful, I will analyze the main points of VoLTE for the subscriber, I will do it using the example of my main number, which works on the MegaFon network.

Most modern smartphones support VoLTE by default, a corresponding icon is shown in the status bar of my Samsung Galaxy S20 Ultra, and there is also a slider in the menu that enables VoLTE.

VoLTE and EVS HD Codec - New Sound Quality. How to include what we get in practice

In older models VoLTE can be found in the network settings, but it is important to note that LTE must be enabled! Oddly enough, this is one of the biggest mistakes that happen to ordinary users, someone “advanced” turns off 4G for them, leaving only 3G for data transmission. This is bad for everyone, as the call quality will be lower. Even if a person does not actively use mobile Internet, it is worth turning on 4G, as this will give an excellent quality of calls – they will be louder, better heard, and you will not have to listen carefully. The absence of extraneous sounds and interference is not only the quality of the microphones in the smartphone, but also the quality of voice transmission on the network. This parameter can be estimated by eye, but why?

To assess the sound of the voice, the Mean Opinion Score (MOS) parameter is used; in Moscow, according to Roskomnadzor in 2019, it was 3.93. This is an average that includes various device models, push-button phones, smartphones, both new and old devices. For example, the MOS value on the MegaFon network for devices with VoLTE and EVS codec support is 4.57. This is noticeably higher than the city average, and this is due to the advanced codec used by the operator.

Before we get to the codec, it’s important to talk about another misconception that exists. Alas, the connection is arranged in such a way that it always adapts to the device with the worst parameters. For example, you call on a push-button phone, where there is no 4G support, and most of the “buttons” are just that. There are no advanced codecs, so the voice quality will be set at the level of this device. When using VoLTE, both smartphones must support this technology, but it must also be enabled on both phones. There is no sense in disconnecting by the user, by default this option is available everywhere, for example, on the same iPhones, nothing needs to be done, the smartphone itself chooses the best sound.

Let’s go back to the EVS (Enhanced Voice Service) codec, it first appeared in Russia in December 2019 on the MegaFon network. Initially, the codec was supported by a number of Sony, Samsung, Huawei and Honor smartphones, since the second half of March, Apple iPhones have been added to them with an iOS update to version 13.4 (support for iPhone 8/8 Plus and newer). It is a new standard and voice quality that is backward compatible with the AMR-WB codec, which is marketed as an HD codec in networks around the world. Let’s take a look at the graph to understand the difference between the codecs.

VoLTE and EVS HD Codec - New Sound Quality. How to include what we get in practice

The first thing worth paying attention to is a different range of transmitted and reproduced frequencies, it is twice as wide – there is an improvement in both low and high frequencies. This allows not only a better voice transmission (AMR-WB does an excellent job with this), but broadcasting from concerts or just listening to music with someone, the transmission quality will be excellent. These words sound great in theory, but how much do they match with practice? My experience with the MegaFon network is that this is indeed the case. The sound vibrates, very lively, several times I specially tried to turn on the music – the feeling that you are near the sound source. If you turn on the speakerphone, then there is no understanding that this is playing, the player is on the phone, or the sound comes from a voice call.

Just like in AMR-WB, there are adaptive technologies, for example, a little noise is mixed during voice transmission. This is necessary because perfect sound quality is not perceived by our ears as correct, we need a little noise to make the sound feel natural. Another feature of the EVS codec is that it adapts to what it “hears”. Every 20 milliseconds, your smartphone analyzes the transmitted signal and changes the quality depending on the conditions, on a noisy street it cuts out extraneous sounds, and in a quiet room where every rustle is important, on the contrary, increases the emphasis on them. This is a smart enough technology that changes the sound depending on dozens of parameters and makes the sound better.

For me, voice calls remain part of the job, and it gets very tiring when the sound in the receiver is not very good, you need to listen carefully. Sometimes I can’t stand it and ask where my interlocutor is – often in response I hear that he is sitting in an office, in a quiet room. But from the sound from the receiver it seems that he is at least outside, where the wind blows into the phone and whistles in my speaker. Some of the problems may be related to hardware, a malfunction of the same microphone (moisture, dust, or simply pierced the microphone, confusing it with the SIM card tray), but often this is also disabled VoLTE on old devices. The situation is gradually improving, but many simply do not know that they can be heard much better and clearer, for many it does not even require changing the smartphone, only turning on the settings if they are disabled for some reason.

For operators, the EVS codec is also good in that it uses half the channel capacity to achieve the same audio quality. And with the same capacity, the quality of speech and sound transmission increases. Look at the two pictures that describe this quality.

VoLTE and EVS HD Codec - New Sound Quality. How to include what we get in practiceVoLTE and EVS HD Codec - New Sound Quality. How to include what we get in practice

The win for EVS is obvious here, it’s just a new generation technology that is already available on the MegaFon network, this operator was the first in Russia to launch this codec. This is important for me, since some of the calls come with the EVS codec, you can feel it during a call. There is no annoying extraneous noise, the audio quality cannot be compared with conventional codecs. On iPhone, there is no display of the codec during a call, while on Samsung it is an HD + icon.

VoLTE and EVS HD Codec - New Sound Quality. How to include what we get in practice

As usual, such a “trifle” as sound quality does not attract the attention of many. My friends who use modern smartphones never paid attention to the possibility of using VoLTE, it seemed to them that this did not affect the quality of speech transmission, that it was about the Internet. This is not true! Therefore, please take a look at whether you have VoLTE enabled or not, and if disabled, then you should enable it, you will make your conversations a little more comfortable. And if your phone works in the MegaFon network, for example, in the capital region, then you have the opportunity to hear how the EVS codec works, I assure you that you will feel this difference instantly, the sound quality is strikingly different. At the same time, the codec is available wherever VoLTE is available on the MegaFon network.

Speech is one of the main functions in a modern smartphone, even if it is not striking. Despite the fact that we write more and more often, we still speak and will speak. Oddly enough, it is VoLTE calls in noisy, difficult conditions that often transmit speech better than just a recorded conversation in a messenger. And this is directly related to the codecs that are used both in hardware and by operators, this is a hardware-software bundle. And I think that we need to use these opportunities, to know about them, they, albeit a little, but improve the quality of our life.


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