How to turn on the AAC codec on Xiaomi Redmi Note 9 Pro: all ways

If you own Xiaomi Redmi Note 9 Pro and notice that the sound quality when connected to wireless headphones or speakers leaves much to be desired, the problem may lie in the audio codec used. By default, many Xiaomi devices based on MIUI use the SBC codec - the standard, but not the best quality option. While AAC (Advanced Audio Codec) provides cleaner sound, especially at high and medium frequencies.

In this article, we’ll look at all the possible ways to force AAC on your Redmi Note 9 Pro, from hidden MIUI settings to third-party apps and system modifications. It’s important to understand that codec support depends not only on your smartphone, but also on the device you’re plugging in (earphones, speakers). If your headphones don’t support AAC, all manipulations will be useless.

Before you start settings, make sure that:

• 📱 Your Redmi Note 9 Pro is running on the current version. MIUI (preferably MIUI 14+ or hyperos).
• 🎧 Connected audio device supports codec AAC (Check the specifications in the instructions).
• 🔄 You rebooted your smartphone after the latest updates – sometimes it solves codec problems.

Why AAC is Better Than SBC and When It Matters

The AAC (Advanced Audio Codec) codec was developed as a successor to MP3 and is today the standard for audio streaming. Compared to the Subband Codec (SBC), which is used by default on most devices, AAC has several key advantages:

Main advantage AAC This is done when listening to music with a high bitrate (for example, FLAC The difference is particularly noticeable on tracks with a rich sound — orchestral music, jazz or modern compositions with deep bass. SBC and AAC minimal.

There are nuances: some users note that on cheap headphones, AAC can sound worse than SBC due to poor implementation of the codec by the manufacturer, and AAC is more demanding of connection stability - with a weak Bluetooth signal, artifacts are possible.

⚠️ Note: If your headphones support aptX or LDAC, Better to use them – these codecs are superior AAC But for Apple devices (AirPods, Beats) AAC It remains the best choice.

Method 1: Enabling AAC through hidden developer settings

The most reliable way to force AAC on the Redmi Note 9 Pro is to use the Developer Menu, which works on most versions of MIUI, but requires developer mode pre-activation.

Steps to include:

1. Open the Settings. → The phone.
2. Find the MIUI version and tap it 7 times in a row, and the notification will appear "You became a developer."
3. Go back to the main Settings menu and find a new Developer section (usually at the bottom of the list).
4. Scroll down to the Network block and select Bluetooth Codecs.
5. In the list of available codecs, tick AAC. If it is not available, then your version of MIUI does not support forced selection.
6. Reboot your smartphone and reconnect the headphones.

Activate the Developer Mode

Check the MIUI version (not lower than 12.5)

Turn off the headphones before changing the settings

Reboot your phone after the changes-->

If there is no Bluetooth Codec in the developer menu, it means that your firmware does not support manual switching, in which case you should try updating MIUI to the latest version or use alternative methods (described below).

⚠️ Note: Some custom firmware (such as LineageOS or Pixel Experience) may not have a codec menu or may not work properly.

Method 2: Use the Bluetooth Codec Changer app

If standard MIUI settings do not allow you to select AAC, you can use a third-party Bluetooth Codec Changer application (available on Google Play), which allows you to force the priority codec for connected devices.

Instructions for setting:

1. Download and install Bluetooth Codec Changer.
2. Launch the application and grant it ADB rights (instructions for obtaining rights will be displayed in the application).
3. In the list of connected devices, select your headphones.
4. In Preferred Codec, select AAC.
5. Press Apply and reconnect the headphones.

The app also shows the current codec used, bitrate and sampling rate, which is useful for checking whether the AAC has actually been activated. If the codec settings have not changed after applying the codec settings, try:

• 🔄 Reboot your smartphone and headphones.
• 📵 Forget the device in Bluetooth settings and connect it again.
• 🔧 In the developer menu, disable the Bluetooth audio codec A2DP (If there is, then turn it back on.

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If the sound becomes intermittent after changing the codec, try to reduce the bitrate in the application settings to 256 kbit / s – this often solves stability problems.

Method 3: Change configuration files (for advanced ones)

If none of the above methods worked, you can try manually editing the system files that handle audio codecs, which requires root rights and is only suitable for advanced users.

Sequence of action:

1. Install a file manager with root support (such as Root Explorer or FX File Explorer).
2. Cross the path: /system/etc/bluetooth/ and find the file. bt_stack.conf.
3. Open the file in the text editor and find the line: BtA2dpSinkCodecsPriority=SBC, AAC,aptX,aptX-HD,LDAC (the order of codecs may differ).
4. Change priority by putting AAC first: BtA2dpSinkCodecsPriority=AAC,SBC,aptX,aptX-HD,LDAC
5. Save the file, set resolutions 644 (rw-r-----).
6. Reboot your smartphone.

On some firmware MIUI file bt_stack.conf In this case, look for the settings in the file. /vendor/etc/bluetooth/bt_vendor.conf or /system/vendor/etc/bluetooth/audio_conf.xml.

⚠️ Warning: Incorrect editing of system files can cause Bluetooth malfunctions.Before making changes, back up the original file!

Checking the current Bluetooth codec

To make sure that AAC is actually used, there are several methods:

1. Through the developer settings: Go to Settings → Developer → Bluetooth Codecs. Connect your headphones and watch the active codec in real time.
2. With Bluetooth Audio Codec Checker, download the utility from Google Play. Launch it and plug in your headphones, and the app will show you the current codec, bitrate and frequency.

Through the Engineering Menu (for Advanced):

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• Enter the code in the dialer.
• Select Phone Information → Bluetooth.
• Find the Audio Codec line.

If the codec has not changed to AAC after all the manipulations, the problem may be:

• 🎧 Headphone incompatibility (check their specifications).
• 📱 Firmware restrictions (some versions) MIUI Blocking the forced codec change).
• 🔄 Conflict with other audio settings (e.g., Dolby Atmos enabled).

Frequent problems and their solutions

Forced AAC activation doesn't always go smoothly, but here are the most common problems and ways to fix them:

If the AAC has failed after all the attempts, it is worth considering the alternatives:

• 🔊 Use it. LDAC (if the headphones support it – it gives better quality, but consumes more battery.
• 🎵 Switch to a wired connection (via USB-C → 3.5 mm adapter).
• 🔄 Update the headphone firmware (if available).

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On the Redmi Note 9 Pro with MIUI 13+, the AAC codec is often activated automatically when you connect Apple devices (AirPods, Beats).

Alternative ways to improve sound

If you can’t turn on the AAC, but you want to improve the sound quality, use these tips:

• 🎛️ Set up the equalizer: In MIUI There is a built-in equalizer (Settings) → Sound. → Try Bass' preset or jazz for a more saturated sound.
• 🔊 Activate Dolby Atmos: Go to Settings → Sound. → Dolby Atmos and select Music or Movie profile.
• 📱 Use your own codecs with Poweramp or Neutron Music Player AAC software level, even if system Bluetooth does not offer it.
• 🔋 Turn off battery optimization for audio applications: Go to Settings → Annexes → Battery management and add player to exceptions.

Also worth paying attention to is the bitrate of the original audio. If you listen to tracks in MP3 128 kbps, the difference between SBC and AAC will be minimal. For a full comparison, use files with a bitrate of 320 kbps or higher.

FAQ: Answers to Frequent Questions