AC4 Xiaomi TVs: Why dialogues have gotten worse and how to fix it

If you recently upgraded your Xiaomi TV or connected it to a new signal source (such as a console or media player), you may have encountered a strange problem: the dialogue in movies and TV shows is barely audible, but the sound effects and music are loud as before. AC4 (Dolby AC-4), This is a technology that is increasingly used in today's streaming and broadcasting services, and in this article, we'll look at what this technology is, why it spoils the sound on Xiaomi TVs, and how to bring back clear dialogue without buying additional hardware.

The problem isn't your hearing or your speakers malfunctioning. AC4 — It's a new generation audio compression format optimized for multi-channel audio with minimal quality loss. TV 4S/5/5X/Q1/Q2 And others don't always decode this codec correctly, especially in terms of dialog processing (central channel), and as a result, the voice of the actors sinks in the overall sound stream, and bass and high frequencies dominate. Fortunately, the problem can be solved at the level of settings, and we'll show you how to do that.

Before we get into the instructions, let's be clear: this is a software problem, not a physical limitation of the speakers. If your TV makes wheezing, crackling, or no sound at all, that's a separate topic that requires a diagnosis of iron. AC4 and the associated nuances of sound.

What is it? AC4 Why is it ruining the dialogue on Xiaomi? TV

Dolby codec AC4 (plainly AC4) It was introduced in 2017 as the successor to the popular Dolby Digital Plus (E-AC3). Its key features:

• 🔹 More efficient compression: allows multichannel audio (up to 7.1.4) to be transmitted with less bitrate, which is critical for streaming services.
• 🔹 Dynamic bitrate distribution: Codec automatically “reassigns” resources between channels depending on the scene (for example, enhances dialogue in quiet moments).
• 🔹 Support for object-oriented sound: unlike traditional channels (left, right, center), AC4 It can work with individual sound objects that move through space.
• 🔹 Backward compatibility: Theoretically, AC4 Decoded on devices that support Dolby Digital Plus, but this doesn’t always work in practice.

So why are the conversations getting quieter? It's all about how Xiaomi TVs handle the central channel (where voices are usually placed). AC4 It uses Dialogue Enhancement technology, which should enhance speech, but many Xiaomi firmware (especially Android-based ones) TV 9/10) They ignore these tags or they're not properly processed:

• 🔊 The voice of the actors sounds muffled, as if from under a blanket.
• 🎵 Music and sound effects remain loud, creating an imbalance.
• 🔄 When switching between sources (e.g. Netflix to YouTube), the volume level jumps.

Besides, AC4 It is often used in conjunction with Dolby Atmos, making it even more difficult for built-in TV decoders. Xiaomi models in the budget and mid-range segment (e.g. Mi). TV A2 "43" or "Redmi Smart" TV X) are not physically able to process the sound, so they simply “reset” some of the data, including amplifying the dialogs.

What are Xiaomi models? TV subject to AC4

The problem is AC4 It's not universal, it depends on the firmware version, the hardware platform, and even the region where the TV is sold. Below is a table of models that users often complain about quiet dialogue:

Note that even within the same model, behaviors can be different. TV 4S 55" on firmware MIUI TV 3.0.25 can reproduce correctly AC4, on MIUI TV 2.1.18 – No. This is because Xiaomi periodically updates audio drivers, but does not always announce changes.

How to check if your TV supports AC4?

1. Open any movie on Netflix or Disney+ Dolby-atmos-labeled.
2. Press the Info (or Display) button on the remote to call the audio information panel.
3. If the "Audio" line is Dolby AC4 or DD+ with AC4, Your TV recognizes it (but not the fact that it reproduces it correctly).

💡

If your Xiaomi TV is released before 2020, it probably won’t support it. AC4 In this case, the sound will be converted to Dolby Digital (AC3), which may lead to artifacts.

Ways to improve dialogues when playing AC4

If your Xiaomi TV is “swallowing” dialogue in movies with the AC4, Try the following methods (from the simplest to the most complex) Start with the software settings, 70 percent of the time it's enough.

1. Enable Clear Voice mode

Many Xiaomi models have a built-in dialog amplification mode that works independently of the codec.

1. Go to Settings → Sound → Sound modes.
2. Select User or Speech (if any).
3. Activate Clear Voice or Enhance Dialogue.
4. Adjust the volume slider of the dialogues (if available) to +3…+6 dB.

If there is no such item, try an alternative path:

• 🔧 On some firmware, the option is hidden in Settings → Special facilities → Audio.
• 🔧 On PatchWall models, look for Dialogue Enhancement in the audio menu.

2.Tune the equalizer manually

If the automatic mode doesn’t help, try raising the average frequencies (where the speech is) manually:

1. Open the settings → Sound → Equator.
2. Select a user profile.
3. Lift sliders in the range of 500 Hz – 2 kHz on +3…+5 dB.
4. Reduce low frequencies (60-150 Hz) by −2 dB to reduce bass "muffling" of voice.

Example of setting up an equalizer for dialogues:

60 Hz: -2 dB




150 Hz: 0 dB




500 Hz: +4 dB




1 kHz: +5 dB




2 kHz: +3 dB




5 kHz: 0 dB




10 kHz: -1 dB

3. disable Dolby processing (if it interferes)

Paradoxically, sometimes Dolby Audio makes the sound worse instead of making it better.

1. Go to Settings → Sound → Additional settings.
2. Turn off the Dolby Audio, Dolby Volume or Auto Volume options.
3. Restart the TV (Settings → Device → Reboot).

Make sure that the problem is only with AC4 (Check out other content)

Update the TV to the latest version

Disable external sound devices (soundbar, headphones)

Reset the sound settings to factory (in the menu "Sound")

-->

4. Update the TV firmware

Xiaomi periodically releases patches for audio drivers, fixing problems with the device AC4. To renew:

1. Go to Settings → About TV → System Update.
2. Click Check for updates.
3. If a new version is available, install it (the TV will restart automatically).

Important: After updating to MIUI TV 3.0.30+ problem AC4 It should disappear on models from 2022 to 2023. Older TVs (2019 to 2020) may require manual firmware through the USB.

5. Use an external decoder (if nothing helps)

If the software methods have not yielded results, there are two options:

• 🔌 Connect AV-receiver or soundbar with support AC4 (for example, Yamaha RX-V4A Or Sonos Beam).
• 🖥️ Use external media player (for example, NVIDIA Shield or Apple TV 4K), which will decode the sound itself.

The connection is carried out through HDMI ARC/eARC Or optical output, in which case the TV will act as a screen only, and the sound processing will be done by an external device.

💡

Before buying an external decoder, make sure it supports AC4 — Not all soundbars and receivers can do this, even if the box says "Dolby Atmos».

Why is the problem with AC4 It is not decided at the level of Xiaomi.

Many users are wondering why Xiaomi is not fixing the problem with the new system. AC4 once and for all:

• 💰 Savings on Licenses: Full Support AC4 Requires Dolby royalties, which increases the cost of TVs. Xiaomi prefers to introduce support gradually, starting with flagship models.
• 🔄 Fragmentation of firmware: Xiaomi TVs are sold in different regions with different versions MIUI TV. A fix for one model can break the sound on another.
• 📉 Development priorities: The company focuses on improving the image (e.g. Dolby Vision), and sound is often left in the background.
• 🛠️ Hardware Restrictions: Older chipsets (e.g. Amlogic) T962) physically incapable of decoding AC4 lossless.

Xiaomi does not always specify in the specifications, whether the model supports the model AC4. For example, in the description of Mi TV Q1 75" may be written "Dolby Audio", but it is not specified which codecs are meant.

According to the report, most of the complaints AC4 It comes from TV owners purchased in 2020-2021, in 2023 models (e.g. Xiaomi) TV A Pro) the problem is less common thanks to updated audio chips.

Frequent errors when setting up the sound on Xiaomi TV

Trying to fix the problem with AC4, Users often make mistakes that only make things worse:

• 🔇 Turn off all sound effects: For example, turning off Dolby Audio can help with the sound. AC4, It will also make you feel worse in other formats (for example, DTS).
• 📶 Reset the sound settings to factory: This will return the equalizer to its original state, where the average frequencies (dialogues) are often understated.
• 🔌 Use it. HDMI-Splitters or extension cords: They may distort the signal AC4, especially if they are not supported HDMI 2.1.
• 🔄 Update firmware through third-party sources: Unofficial firmware may contain errors in audio drivers, which will lead to complete loss of sound.

Also a common mistake is to try to solve an application-level problem (like Netflix settings).

• 🎬 Netflix, Disney+ and other services cannot be disabled AC4 For your device, the sound format is determined by the server.
• 🔊 The volume settings inside the app (like Netflix’s “Dialogue Level”) work only for mobile, not Android. TV.

💡

If the sound has become worse after the changes, return the sound settings to the original state: go to Settings → Sound. → Resetting the sound settings.

Alternative solutions: audio conversion and external devices

If none of the proposed methods worked, consider the following options:

1. Conversion AC4 into AC3 fly-by

Some media players (such as Kodi or VLC) They can transcode sound in real time:

1. Install Kodi from Google Play on your TV.
2. Go to Settings. → Player. → Audio.
3. Enable the option to Enable audio transcoding.
4. In the Audio Codec field, select AC3.

The disadvantage of the method: possible sound delays (up to 0.5-1 seconds) and loss of quality.

2.Use of TV-support-box AC4

If the TV can't decode, you can have it done with an external device.

• 📦 NVIDIA Shield TV Pro - supports AC4 Dolby Atmos has its own audio processor.
• 🍎 Apple TV 4K — handle AC4, It requires a subscription to the Apple ecosystem.
• 🤖 Xiaomi Mi Box S is a budget option, but AC4 Supports only in beta firmware.

The connection is carried out through HDMI (port HDMI IN After you've connected:

1. In the settings of the TV, select the external sound source: Settings → Sound. → Audio output → HDMI ARC.
2. In the settings of the consoles, activate Passthrough for AC4.

Optical output + external DAC

If your TV is equipped with optical output (S/PDIF), You can connect an external DAC (for example, Topping). D10s fiiO D3) This method is suitable for audiophiles, but requires additional costs (from the beginning of the process). 3 000 ruble).

The advantage of optical output is that it transmits a “pure” digital signal without distortions that can occur during transmission. HDMI.

💡

Before buying an external device, check if it supports AC4 — budgetary TV-The boxes and soundbars only work with Dolby Digital (AC3) and DTS.

FAQ: Frequent questions about AC4 Xiaomi TV