ViPER4Android

Material Design 3 UI for ViPER4Android FX. Full feature set of the ViPER4Android DSP engine with a modern interface.

Features

Audio Effects

• Output Volume / Channel Pan / Limiter
• Playback Gain Control (AGC)
• LUFS Targeting
• Multiband Compressor (5-band)

• FET Compressor

• ViPER Bass (Natural / Pure Bass+ / Subwoofer)

• ViPER Bass Mono (original v0.5.0 algorithm)
• Psychoacoustic Bass Enhancement
• ViPER Clarity (Natural / OZone+ / XHiFi)
• Tube Simulator

• AnalogX

• ViPER-DDC (Digital Device Correction)

• Spectrum Extension (VSE)
• IIR Equalizer (10 / 15 / 25 / 31 bands)

• Dynamic EQ (up to 10 bands, per-band threshold/attack/release)

• Convolver (IRS impulse response loading)

• Field Surround (Colorful Music)
• Differential Surround
• Stereo Imager (3-band width control)
• Headphone Surround+ (VHE)
• Reverberation

• Dynamic System (headphone virtualization)

• Auditory System Protection (Cure crossfeed)

• Speaker Optimization (speaker-only)

App Features

• Material Design 3 with dynamic theming
• AIDL and legacy (non-AIDL) HAL support
• Per-device profile management and auto switching
• Preset import / export
• Global mode and per-app mode
• In-app log viewer (tap Driver Version 7 times in Settings)
• Audio effects documentation (long press each effect)
• In-app update checker (press app version in Settings)

Installation

1. Download the latest APK from the Releases
2. Install the APK
3. Flash the Magisk module from ViPERFX_RE (or the AIDL variant)
4. Reboot
5. Open the app and tune the settings.
6. Enjoy

Q&A

• What is Global Mode?

  Creates a single AudioEffect on session ID 0 (the global mix). The Android audio framework routes all audio through session 0, so one effect instance processes everything. This is the simplest and most compatible mode.

• What is Per-App Mode?

  Creates a separate AudioEffect for each audio player's session ID. The DSP processes each app's audio independently. Requires either root or installation as a privileged system app (see below).

• Why does Per-App Mode require root (or a system-app install)?

  On modern Android (API 34+ / Android 14+), the framework no longer broadcasts OPEN_AUDIO_EFFECT_CONTROL_SESSION, and AudioManager.getActivePlaybackConfigurations() returns anonymized session IDs (sessionId:0, u/pid:-1/-1) to ordinary apps. The app uses AudioPlaybackCallback to detect playback state changes, then needs a privileged path to recover the real session ID. Two paths are supported:

  • Root (default): the real session ID is read via su -c "dumpsys audio".
  • Privileged system app (no root): if the app is installed under /system/priv-app and granted the MODIFY_AUDIO_ROUTING permission, the framework returns the real (non-anonymized) sessionId/clientUid directly from getActivePlaybackConfigurations(), so no root and no dumpsys shell-out is needed. The app auto-detects this at runtime (the permission grant is the trigger) and prefers it over the root path.

• How do I install as a privileged system app (per-app mode without root)?

  Place the APK in /system/priv-app/ViPER4Android/ and add a privileged-permission allowlist so the OS grants MODIFY_AUDIO_ROUTING:

  xml <!-- /system/etc/permissions/privapp-permissions-viper4android.xml --> <?xml version="1.0" encoding="utf-8"?> <permissions> <privapp-permissions package="com.llsl.viper4android"> <permission name="android.permission.MODIFY_AUDIO_ROUTING"/> </privapp-permissions> </permissions>

  This is done for you when the app ships inside a ROM or a Magisk module that mounts it systemlessly. Without the allowlist entry the permission is silently denied (with ro.control_privapp_permissions=enforce, the default), and the app falls back to the root path. No platform signature is required, priv-app placement satisfies the privileged half of the signature|privileged protection level.

  Note that you may need allow the following SElinux rules for the app (as system app) to work:

  sh allow priv_app servicemanager service_manager list allow priv_app viper_control_service service_manager find allow priv_app default_android_service service_manager find allow priv_app hal_audio_default binder { call transfer }

• What is Per-Device Profile?

  Each audio device (e.g., "Galaxy Buds Pro", "Airpods", "Speaker") keeps its own saved effect settings, loaded automatically on connect and saved when the app goes to the background. See Per-Device Profiles for details.

• What is AIDL Mode? > Android 14+ introduced a new Audio HAL interface based on AIDL (Android Interface Definition Language), > replacing the legacy HIDL interface. The App automatically check which HAL your device using.

Presets

Presets are stored in the v2 grouped-JSON format (schemaVersion: 2.1):

v2.1 stores the raw semantic values that send to the DSP

{
  "schemaVersion": 2.1,
  "name": "My Preset",
  "equalizer": { "enable": true, "bandCount": 10, "bands": [3.0, 2.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 2.0, 3.0], "presetId": null },
  "dynamicEq": { "enable": false, "bandCount": 4, "freqs": [...], "gains": [...] },
  "ddc": { "enable": false, "device": "" }
}

Migrating v1 / legacy presets to v2 and v2.1

v2 is not compatible with the old flat v1 JSON or the legacy ViPER4Android XML presets. Two migration paths are available:

1. In-app export (recommended). In the last v1 app release (1.5.5), use Export preset as v2 to produce a .v2.json file, then import it in v2.

2. Command-line tool. For v1 JSON or legacy XML presets, use tools/convert_preset.py (Python 3.11+):

   ```bash

   v1 flat JSON -> v2.1

   python3 tools/convert_preset.py preset.json --to 2.1 -o preset.v2.json

   legacy ViPER4Android XML -> v2.1

   python3 tools/convert_preset.py preset.xml --to 2.1 -o preset.v2.json

   v2 -> v2.1

   python3 tools/convert_preset.py preset.v2.json -o preset.v2_1.json ```

The input format (v1 JSON vs. XML) and, for v1 JSON, the headphone/speaker namespace are auto-detected. Missing fields are filled with the app defaults. Import the resulting .v2.1.json in the app.

[!NOTE] v2 no longer stores separate headphone and speaker copies inside a preset. A preset now holds a single unified effect state and is applied to a device through the per-device profile system.

Per-Device Profiles

Each audio output device keeps its own full effect profile. When you switch outputs, the app automatically loads the incoming device's profile, so your speaker, wired earphones, and each pair of Bluetooth buds all remember their own tuning.

How a device is identified

The active output is detected from the Android audio routing API, and each device gets a stable deviceId:

• Speaker → speaker
• Wired headphone / headset → wired_headphone
• Bluetooth (A2DP / BLE / hearing aid) → the device's MAC address (falls back to bt_<id> if unavailable)
• USB DAC / headset → the USB device address (falls back to usb_<id>)

Because Bluetooth and USB devices are keyed by their hardware address, two different pairs of buds are stored separately, and reconnecting the same device restores exactly its profile. The display name comes from the device's reported product name (e.g. "Galaxy Buds Pro"), with a type-based fallback ("Bluetooth A2DP", "USB Audio", ...).

When profiles are saved and loaded

• On output switch: the app detects the new active device, loads its profile.
• On app background (home button, app switch / ON_STOP) and on shutdown: the current settings are saved to the active device's profile.
• First time a device is seen: a profile is created automatically from the current settings.

Managing profiles

Open the Devices dialog to manage saved profiles. There you can save the current settings to a device, load a device's profile into the current settings, rename a device, or delete a profile. Deleting a profile removes its saved settings, the device gets a fresh profile the next time it connects.

Root Access

This app may require root access for:

• Per-App Mode: Retrieving real audio session IDs via dumpsys (not needed when installed as a privileged system app, see Per-App Mode in the Q&A)
• Debug log viewer: Reading logcat for driver diagnostics

Please make sure the source of any modified APK is trustworthy to avoid any security risks.

Contributing

Contributions are welcome. Open an issue or submit a pull request.

Localization

To help with translations, follow the template guide.

• RU: @maurerdv
• ZH-CN: @Arissekai