phhusson/ims — VoLTE for LineageOS on Samsung devices

Note: For production use, prefer the krazey-ims fork. It has a better structure, more fixes, and is hardware-agnostic. This repo is kept primarily as a guide for device tree integration and audio issue debugging on devices with similar Samsung binaries.

Open-source SIP/IMS stack for LineageOS, based on phhusson/ims. Tested on Samsung Galaxy A21s (SM-A217F) running LineageOS 23.2 (Android 16) with O2 Germany.

How it works

The Android telephony framework requires a privileged system app that implements android.telephony.ims.ImsService and is registered as the MmTel provider. This app provides a pure-userspace SIP/IMS stack: it opens the IMS bearer, discovers the P-CSCF, performs SIP AKA registration, and handles voice calls over RTP.

Prerequisites

After cloning (whether via repo sync, git clone, or roomservice), initialize the rnnoise submodule — repo sync does not do this automatically:

cd packages/apps/PhhIms
git submodule update --init app/jni/rnnoise

Building in-tree (LineageOS / AOSP)

Add this repo to your local manifest or lineage.dependencies:

<!-- .repo/local_manifests/roomservice.xml -->
<project path="packages/apps/PhhIms" remote="github" name="amikhasenko/ims" revision="main" />

// lineage.dependencies
{
    "repository": "amikhasenko/ims",
    "target_path": "packages/apps/PhhIms",
    "branch": "main"
}

The Android.bp uses platform_apis: true, which gives access to all internal framework APIs (Rlog, MmTelFeature, ImsConfigImplBase, etc.) without patching android.jar. No Gradle build or SDK modification is needed.

Device tree integration (Samsung Exynos example: A21s)

The following shows the full diff needed in your device tree. Adapt paths and package names for your device.

If you have the same device, apply the patch to device_a21s_common repository.

common.mk (or device.mk)

# IMS over Wi-Fi data service and network qualification service.
# Required by the telephony framework even for VoLTE-only (no VoWiFi):
# without these, DataServiceManager and NetworkRegistrationManager fail
# to bind their WLAN handlers, which can cascade to IMS setup failures.
PRODUCT_PACKAGES += \
    Iwlan \
    QualifiedNetworksService

# Tell the framework VoLTE is available even if the carrier config says otherwise.
# Required because carrier config defaults to volte_available=false for unknown carriers.
PRODUCT_PROPERTY_OVERRIDES += \
    persist.dbg.volte_avail_ovr=1 \
    persist.dbg.wfc_avail_ovr=1 \
    persist.dbg.allow_ims_off=1

PRODUCT_PACKAGES += \
    PhhIms

PRODUCT_COPY_FILES += \
    $(COMMON_PATH)/privapp-permissions-me.phh.ims.xml:$(TARGET_COPY_OUT_SYSTEM)/etc/permissions/privapp-permissions-me.phh.ims.xml

overlay/frameworks/base/core/res/res/values/config.xml

<!-- Tell the platform VoLTE and VT are available on this device -->
<bool name="config_carrier_volte_available">true</bool>
<bool name="config_device_volte_available">true</bool>
<bool name="config_device_vt_available">true</bool>

<!-- IMS bearer management services -->
<string name="config_wlan_data_service_package">com.google.android.iwlan</string>
<string name="config_wlan_network_service_package">com.google.android.iwlan</string>
<string name="config_qualified_networks_service_package">com.android.telephony.qns</string>

overlay/packages/services/Telephony/res/values/config.xml

<!-- Register me.phh.ims as the IMS MmTel provider -->
<string name="config_ims_mmtel_package" translatable="false">me.phh.ims</string>

privapp-permissions-me.phh.ims.xml

<?xml version="1.0" encoding="utf-8"?>
<permissions>
    <privapp-permissions package="me.phh.ims">
        <permission name="android.permission.READ_PRIVILEGED_PHONE_STATE"/>
        <permission name="android.permission.MODIFY_PHONE_STATE"/>
    </privapp-permissions>
</permissions>

sepolicy/vendor/property.te

vendor_internal_prop(vendor_ims_prop)

sepolicy/vendor/property_contexts

# IMS
vendor.ril.ims.                u:object_r:vendor_ims_prop:s0

sepolicy/vendor/sehradiomanager.te

allow sehradiomanager vendor_ims_prop:property_service set;

configs/mixer/mixer_paths.xml — the audio fix

During a SIP/VoLTE call the Samsung audio HAL applies the communication-handset-mic path, which contains route-apcall-mic. This path tells the ABox DSP to route mic audio to the modem/VSS path. During a software IMS call there is no modem audio on this path, so the captured audio is silent.

The fix is to replace route-apcall-mic with route-ap-record (the normal capture path) in all communication-*-mic paths. This tells the DSP to keep routing mic audio to calliope_10 (pcm110c), which is where the HAL opens the capture stream.

--- a/configs/mixer/mixer_paths.xml
+++ b/configs/mixer/mixer_paths.xml
@@ -1407,15 +1407,13 @@
 
 	<path name="communication-handset-mic">
 		<path name="dev-dual-mic" />
-		<path name="set-call-wdma4-16bit-config" />
-		<path name="route-apcall-mic" />
+		<path name="route-ap-record" />
 		<ctl name="ABOX Sound Type" value="VOICE" />
 	</path>
 
 	<path name="communication-speaker-mic">
 		<path name="dev-dual-invert-mic" />
-		<path name="set-call-wdma4-16bit-config" />
-		<path name="route-apcall-mic" />
+		<path name="route-ap-record" />
 		<ctl name="ABOX Sound Type" value="SPEAKER" />
 	</path>
 
@@ -1429,8 +1427,7 @@
 
 	<path name="communication-headset-mic">
 		<path name="dev-headset-mic" />
-		<path name="set-call-wdma4-16bit-config" />
-		<path name="route-apcall-mic" />
+		<path name="route-ap-record" />
 		<ctl name="ABOX Sound Type" value="HEADSET" />
 	</path>

Cellular calls use separate incall-* paths and are unaffected.

No binary patching or framework patches are needed.

Required binary patches

None. Earlier versions required patching libaudioproxy.so to change the ALSA device selection, but the real fix is in the mixer path configuration above.

Reverse-engineering notes for the Samsung audio HAL are kept in RE/README.md for reference.

Required framework patches

None. Earlier versions required a patch in packages/services/Telecomm to use MODE_IN_COMMUNICATION instead of MODE_IN_CALL. With the current fork the framework correctly receives the IMS call state and sets the mode appropriately. The mixer path fix alone is sufficient.

Current status

Feature	Status
Registration	Works (initial and periodic re-REGISTER both succeed)
Incoming SMS	Works
Outgoing SMS	Not tested
Incoming Calls	Fix for "dropped after accept" committed; needs device verification
Outgoing Calls	Works with mixer_paths.xml fix
Mic audio during call	Works with mixer_paths.xml fix
Video recording	Works (stock path, unaffected)
Voice Recorder	Works (stock path, unaffected)

Building with Gradle

The public android.jar (API 33) stubs do not expose the internal IMS APIs. To build with Gradle you need a full android.jar built from AOSP sources in app/libs/android.jar, and the SDK jar must have MmTelFeature removed to avoid duplicate class conflicts:

zip -d ./platforms/android-33/android.jar \
    android/telephony/ims/feature/MmTelFeature.class \
    'android/telephony/ims/feature/MmTelFeature$MmTelCapabilities.class'

For production builds use the in-tree Soong build instead.

Notes

• The app has no launcher icon and does not appear in the app drawer.
• On carriers where the RIL does not report P-CSCF addresses via LinkProperties, DNS discovery is attempted using the standard 3GPP domain (TS 23.003 §13.2): ims.mnc<MNC>.mcc<MCC>.3gppnetwork.org. A last-resort override is available via adb shell setprop persist.ims.pcscf_fallback <ip>.
• VoLTE must be enabled via ADB once after installing:

  adb shell settings put global enhanced_4g_mode_enabled 1
  

  On a fresh install this defaults to on.