Modern Xiaomi and Redmi smartphones offer many hidden features that often go unnoticed by users, although they significantly affect the comfort of communication. One of these features is HD Voice technology, which is displayed in the status bar of the device in the form of a small but important HD icon. Many gadget owners see this icon, but do not fully understand its practical benefits and technical background of work.
In the basic sense, standard voice calls use a narrowband audio codec that limits the frequency range of the audio transmitted, which leads to the voice of the interlocutor sounds deaf, with characteristic metallic hues and distortions, especially in poor reception conditions. HD Call technology, based on the VoLTE standard (Voice over LTE), radically changes the approach to voice transmission using broadband sound.
The result of this technology is crystal clear sound, which allows you to distinguish not only words, but also intonations, as well as background noise, making the conversation as close as possible to real communication in the same room. For owners of Xiaomi this is especially important, since the interface MIUI and HyperOS provide flexible settings for managing communication quality, allowing the user to independently control the parameters of the connection.
Technology Basics of HD Voice and VoLTE
The fundamental difference between HD calls and traditional telephony is the shift from circuit switching to packet data. Whereas voice was previously transmitted over a dedicated bandwidth-limited line, it is now encoded into digital packets and transmitted over a fourth-generation LTE network. This allows for more advanced codecs such as AMR-WB (Adaptive Multi-Rate Wideband), which support the frequency range from 50 Hz to 7000 Hz.
To implement this feature on Xiaomi smartphones, not only does it require support from the carrier, but also the appropriate modem setting in the device itself. The audio encoding process takes place in real time, which requires stable connection and minimal delays, which is why the quality of HD calls depends on the coverage of the 4G network in your region.
⚠️ Attention: Use HD Voice may slightly increase battery consumption in areas of uncertain network reception 4G, The modem is in constant data transmission mode even during voice conversation.
It’s important to understand that VoLTE technology allows voice and data to be transmitted simultaneously, which means that when you’re talking in high quality, your Internet doesn’t switch to a slow 2G or 3G standard, but continues to run at high speed LTE. For gaming or navigation, this is a critical aspect that is often overlooked when discussing communication quality.
Technical details of codecs
Key Benefits of Using HD Calls
The switch to HD Call on Xiaomi devices offers a number of tangible benefits that are noticeable after the first minutes of communication, primarily in terms of speech intelligibility. In noisy places, such as a high-traffic street or shopping center, broadband audio helps to better filter the useful signal from background noise.
In addition, the technology allows you to reduce the time of connection. Post dialing beep is heard almost instantly after pressing the call button, which saves user time, and it is worth noting the possibility of conducting high-resolution video calls directly through a standard "bell ringer", if the operator and the interlocutor support ViLTE (Video over LTE).
- 🎙️ High definition: The voice sounds natural, without the characteristic "telephone" effect, which reduces fatigue during long conversations.
- 📶 Simultaneous operation of voice and the Internet: the ability to use the navigator or messengers during a conversation without falling speed to the Internet EDGE.
- 🔋 Efficient use of resources: Modern modems Xiaomi optimized for networking LTE, It is often more energy efficient than switching between 3G and 4G.
The focus is on how HD Voice affects the coverage inside buildings. LTE signals often penetrate walls better than old standards, allowing you to stay connected in basements or deep offices where normal calls can break, making the technology indispensable for business people, who are often in business centers with complex architectures.
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The main advantage of HD calls is not just "best sound", but the ability to fully use the mobile Internet in parallel with voice communication without losing the quality of the connection.
How to enable HD call to Xiaomi and Redmi
Activation of the function HD Call on Xiaomi smartphones usually happens automatically when installed SIM-However, depending on the firmware version (Global, China, Russia) and regional settings, the activation menu may be located in different places. 4G (LTE).
The standard activation path is as follows: open Settings, go to the section SIM-Select the SIM card you want if there are two and find the switch Use VoLTE or Calls via LTE. In some shells MIUI This item can be hidden in the menu Additional settings inside the SIM card section.
☑️ Verification of activation HD Voice
If you don't find the VoLTE switch in the standard menu, it may be hidden by the engineering menu or requires activation through hidden settings. On some global versions of firmware for Russian operators, the function is turned on by default and does not have a manual switch - the HD indicator will appear itself when you register with the network. For forced activation, you can use the code # # #86583#, which includes a hidden VoLTE Carrier switch in the engineering menu.
Once you enter the code, you should see the message "VoLTE Carrier check was disabled" (which means you turn on the check and therefore activate the function). After that, restart the device. If the HD indicator does not appear, try entering the code ##4636##, select Phone Information and find the VoLTE Provisioned switch there, turning it into an active state.
⚠️ Note: Entering commands in the engineering mode can cause the radio module to work unstable if you change unfamiliar parameters.
Why HD Call is not working: the main reasons
Even with a supported Xiaomi smartphone and feature enabled, the HD icon may not appear.The most common reason is the lack of VoLTE support from your mobile operator in a particular region. Not all base stations are equipped with the necessary hardware to transmit voice over LTE, especially in remote areas.
The second important factor is type SIM-Older SIM cards issued years ago may not have a profile to work on networks 4G In this case, you need to contact the salon for a free replacement. SIM-new card with support USIM VoLTE.
- 🚫 No subscription: For some operators, VoLTE is a paid option or requires an additional tariff package.
- 📱 Two-Sim mode: On some models Redmi and Poco with active mode of two SIM cards HD It can only work on one of them or shut down completely when you call the other.
- 🌍 Regional restrictions: Global firmware versions may not have local carrier certifications, leaving the feature hidden.
It is also important to note that during roaming the function HD Call almost never works, as it requires an agreement between operators of different countries on the routing of voice traffic through the Internet. IP-In such cases, the phone will automatically switch to standard protocols. 2G or 3G linkage.
Comparison of quality of communication: HD vs. Normal call
To make an objective assessment of the differences between technologies, consider key parameters that affect user experience: Regular call (GSM/3G) uses narrowband sound, which limits the transmission of high and low frequencies, which makes speech less natural and makes it difficult to recognize similar sounding consonants.
The table below provides a detailed comparison of the characteristics of the two types of connection, which will help to understand the technical difference:
| Parameter | Regular call (2G/3G) | HD Call (VoLTE) |
|---|---|---|
| Frequency range | 300 Hz - 3400 Hz | 50 Hz - 7,000 Hz |
| Connection time | 7-10 seconds. | 1-2 seconds |
| The Internet | Reduced to 2G/3G | Stays on 4G/LTE |
| Codec | NB-AMR | WB-AMR (HD Voice) |
As you can see from the data, the frequency difference is more than twofold, allowing you to transmit sounds like "s", "s", "f" much more clearly, which is especially important for people with hearing impairments or when speaking in foreign languages. In addition, the speed of establishing connections in LTE networks is much faster, which eliminates long horns before starting a conversation.
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To check the sound quality, ask the interlocutor to pronounce words with hissing sounds ("brush", "life") - in HD mode they will be heard clearly, without the characteristic hissing and distortion.
Customization of sound parameters and troubleshooting
If HD calls work but you don't like the sound quality, you should check the additional settings of the smartphone. In the section Sound and vibration on Xiaomi devices, there are often noise reduction settings. Sometimes aggressive noise cancellation can "cut" frequencies, making the voice unnatural even in HD mode.
In some cases, resetting the network to factory settings helps. → The phone. → All specs → Status SIM-maps (the path may vary depending on the version) MIUI) And find the reset option. An easier way is to turn on the flight mode. 10-15 seconds, and then turn it off, which will force the phone to re-register in the network and choose the optimal communication protocol.
If the problem is a modem software failure, updating the firmware to the latest available version can help. Xiaomi engineers regularly release patches that improve compatibility with local carrier networks, and it is worth checking for updates to the Google Play Services component, which can affect the operation of network services.
⚠️ Note: When resetting network settings, stored Wi-Fi passwords and associated Bluetooth devices will be deleted, so write down the necessary data in advance.