diff --git a/CHANGELOG.md b/CHANGELOG.md
index 580e915d3cdbf56ae3e1051e6386f17e55f93520..280f099aa11e683b963fe4074217f8263a08b583 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Event content types for VOIP.
+
 ### Changed
 
 - `AccessTokenAuthenticationFunction` now allows servers to set `soft_logout`.
diff --git a/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/ClientEvent.kt b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/ClientEvent.kt
index 8ca29a7432ab6103bbce85ecbb56162540151bfa..ad51c5383d4254a789dbb87c1ece89e162f446bb 100644
--- a/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/ClientEvent.kt
+++ b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/ClientEvent.kt
@@ -7,11 +7,16 @@ import net.folivo.trixnity.core.model.RoomId
 import net.folivo.trixnity.core.model.UserId
 
 /**
- * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#types-of-room-events">matrix spec</a>
+ * A client event with a specific type given by the generic parameter C.
+ *
+ * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#events">Matrix events</a>
  */
 sealed interface ClientEvent<C : EventContent> : Event<C> {
     /**
-     * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#room-event-fields">matrix spec</a>
+     * Matrix room event. Either a message event or a state event.
+     *
+     * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#types-of-room-events">Types of matrix room events</a>
+     * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#room-event-format">Matrix room event format</a>
      */
     sealed interface RoomEvent<C : RoomEventContent> : ClientEvent<C> {
         val id: EventId
@@ -20,6 +25,12 @@ sealed interface ClientEvent<C : EventContent> : Event<C> {
         val originTimestamp: Long
         val unsigned: UnsignedRoomEventData?
 
+        /**
+         * Matrix message event
+         *
+         * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#types-of-room-events">Types of matrix room events</a>
+         * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#room-event-format">Matrix room event format</a>
+         */
         @Serializable
         data class MessageEvent<C : MessageEventContent>(
             @SerialName("content") override val content: C,
@@ -31,7 +42,10 @@ sealed interface ClientEvent<C : EventContent> : Event<C> {
         ) : RoomEvent<C>
 
         /**
-         * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#types-of-room-events">matrix spec</a>
+         * Matrix state event
+         *
+         * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#types-of-room-events">Types of matrix room events</a>
+         * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#room-event-format">Matrix room event format</a>
          */
         @Serializable
         data class StateEvent<C : StateEventContent>(
diff --git a/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/EventContent.kt b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/EventContent.kt
index 29d4fb1a47ae823c6d3c5b995d54de04885194bb..69234568bacc22331917fa4d11e79d110001b6ba 100644
--- a/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/EventContent.kt
+++ b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/EventContent.kt
@@ -7,6 +7,11 @@ import net.folivo.trixnity.core.model.events.m.RelatesTo
 
 sealed interface EventContent
 
+/**
+ * Content of a matrix room event
+ *
+ * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#types-of-room-events">Types of matrix room events</a>
+ */
 sealed interface RoomEventContent : EventContent {
     /**
      * @see <a href="https://spec.matrix.org/v1.10/application-service-api/#referencing-messages-from-a-third-party-network">matrix spec</a>
@@ -14,11 +19,17 @@ sealed interface RoomEventContent : EventContent {
     val externalUrl: String?
 }
 
+/**
+ * Content of a matrix message event
+ */
 interface MessageEventContent : RoomEventContent {
     val relatesTo: RelatesTo?
     val mentions: Mentions?
 }
 
+/**
+ * Content of a matrix state event
+ */
 interface StateEventContent : RoomEventContent
 
 interface ToDeviceEventContent : EventContent
diff --git a/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/m/call/CallEventContent.kt b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/m/call/CallEventContent.kt
new file mode 100644
index 0000000000000000000000000000000000000000..67c789cbaec9faac38a72972a9dcf556412187a3
--- /dev/null
+++ b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/m/call/CallEventContent.kt
@@ -0,0 +1,266 @@
+package net.folivo.trixnity.core.model.events.m.call
+
+import kotlinx.serialization.EncodeDefault
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.descriptors.buildClassSerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.json.JsonDecoder
+import kotlinx.serialization.json.jsonPrimitive
+import net.folivo.trixnity.core.model.events.MessageEventContent
+import net.folivo.trixnity.core.model.events.m.Mentions
+import net.folivo.trixnity.core.model.events.m.RelatesTo
+
+/**
+ * Matrix call event content
+ *
+ * @see <a href="https://spec.matrix.org/v1.1/client-server-api/#voice-over-ip">matrix spec</a>
+ */
+sealed interface CallEventContent : MessageEventContent {
+    val callId: String
+    val version: String
+    val partyId: String?
+
+    /**
+     * Matrix call invite content
+     *
+     * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#mcallinvite">matrix spec</a>
+     */
+    @Serializable
+    data class Invite(
+        @Serializable(with = VersionSerializer::class)
+        @SerialName("version") override val version: String,
+        @SerialName("call_id") override val callId: String,
+        @SerialName("party_id") override val partyId: String? = null,
+        @SerialName("invitee") val invitee: String? = null,
+        @SerialName("lifetime") val lifetime: Long,
+        @SerialName("offer") val offer: Offer,
+
+        // Added in v1.10:
+        @SerialName("sdp_stream_metadata") val sdpStreamMetadata: Map<String, StreamMetadata>?,
+    ) : CallEventContent {
+        override val externalUrl: String? = null
+        override val relatesTo: RelatesTo? = null
+        override val mentions: Mentions? = null
+
+        @Serializable
+        enum class OfferType {
+            @SerialName("offer") OFFER,
+        }
+
+        @Serializable
+        data class Offer(
+            @SerialName("sdp") val sdp: String,
+            @SerialName("type") val type: OfferType,
+        )
+    }
+
+    /**
+     * Matrix call candidates content
+     *
+     * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#mcallcandidates">matrix spec</a>
+     */
+    @Serializable
+    data class Candidates(
+        @Serializable(with = VersionSerializer::class)
+        @SerialName("version") override val version: String,
+        @SerialName("call_id") override val callId: String,
+        @SerialName("party_id") override val partyId: String? = null,
+        @SerialName("candidates") val candidates: List<Candidate>,
+    ) : CallEventContent {
+        override val relatesTo: RelatesTo? = null
+        override val mentions: Mentions? = null
+        override val externalUrl: String? = null
+
+        @Serializable
+        data class Candidate(
+            @SerialName("candidate") val candidate: String,
+            @SerialName("sdpMLineIndex") val sdpMLineIndex: Long? = null,
+            @SerialName("sdpMid") val sdpMid: String? = null,
+        )
+    }
+
+    /**
+     * Matrix call answer content
+     *
+     * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#mcallanswer">matrix spec</a>
+     */
+    @Serializable
+    data class Answer(
+        @Serializable(with = VersionSerializer::class)
+        @SerialName("version") override val version: String,
+        @SerialName("call_id") override val callId: String,
+        @SerialName("party_id") override val partyId: String? = null,
+        @SerialName("answer") val answer: Answer,
+
+        // Added in v1.10:
+
+        @SerialName("sdp_stream_metadata") val sdpStreamMetadata: Map<String, StreamMetadata>? = null,
+    ) : CallEventContent {
+        override val relatesTo: RelatesTo? = null
+        override val mentions: Mentions? = null
+        override val externalUrl: String? = null
+
+        @Serializable
+        enum class AnswerType {
+            @SerialName("answer") ANSWER,
+        }
+
+        @Serializable
+        data class Answer(
+            @SerialName("sdp") val sdp: String,
+            @SerialName("type") val type: AnswerType,
+        )
+    }
+
+    /**
+     * Matrix call hangup content
+     *
+     * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#mcallhangup">matrix spec</a>
+     */
+    @Serializable
+    data class Hangup(
+        @Serializable(with = VersionSerializer::class)
+        @SerialName("version") override val version: String,
+        @SerialName("call_id") override val callId: String,
+        @SerialName("party_id") override val partyId: String? = null,
+        @SerialName("reason") val reason: Reason? = null,
+    ) : CallEventContent {
+        override val relatesTo: RelatesTo? = null
+        override val mentions: Mentions? = null
+        override val externalUrl: String? = null
+
+        @Serializable
+        enum class Reason {
+            @SerialName("ice_failed") ICE_FAILED,
+            @SerialName("invite_timeout") INVITE_TIMEOUT,
+            // Added in v1.7:
+            @SerialName("ice_timeout") ICE_TIMEOUT,
+            @SerialName("user_hangup") USER_HANGUP,
+            @SerialName("user_media_failed") USER_MEDIA_FAILED,
+            @SerialName("user_busy") USER_BUSY,
+            @SerialName("unknown_error") UNKNOWN_ERROR,
+        }
+    }
+
+    // Added in v1.7:
+
+    /**
+     * Matrix call negotiate content
+     *
+     * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#mcallnegotiate">matrix spec</a>
+     */
+    @Serializable
+    data class Negotiate(
+        @EncodeDefault
+        @Serializable(with = VersionSerializer::class)
+        @SerialName("version") override val version: String = "1",
+        @SerialName("call_id") override val callId: String,
+        @SerialName("party_id") override val partyId: String,
+        @SerialName("description") val description: Description,
+        @SerialName("lifetime") val lifetime: Long,
+
+        // Added in v1.10:
+
+        @SerialName("sdp_stream_metadata") val sdpStreamMetadata: Map<String, StreamMetadata>? = null
+    ) : CallEventContent {
+        override val relatesTo: RelatesTo? = null
+        override val mentions: Mentions? = null
+        override val externalUrl: String? = null
+
+        @Serializable
+        enum class DescriptionType {
+            @SerialName("offer") OFFER,
+            @SerialName("answer") ANSWER
+        }
+
+        @Serializable
+        data class Description(
+            @SerialName("sdp") val sdp: String,
+            @SerialName("type") val type: DescriptionType,
+        )
+    }
+
+    /**
+     * Matrix call reject content
+     *
+     * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#mcallreject">matrix spec</a>
+     */
+    @Serializable
+    data class Reject(
+        @EncodeDefault
+        @Serializable(with = VersionSerializer::class)
+        @SerialName("version") override val version: String = "1",
+        @SerialName("call_id") override val callId: String,
+        @SerialName("party_id") override val partyId: String,
+    ) : CallEventContent {
+        override val relatesTo: RelatesTo? = null
+        override val mentions: Mentions? = null
+        override val externalUrl: String? = null
+    }
+
+    /**
+     * Matrix call select answer content
+     *
+     * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#mcallselect_answer">matrix spec</a>
+     */
+    @Serializable
+    data class SelectAnswer(
+        @EncodeDefault
+        @Serializable(with = VersionSerializer::class)
+        @SerialName("version") override val version: String = "1",
+        @SerialName("call_id") override val callId: String,
+        @SerialName("party_id") override val partyId: String,
+        @SerialName("selected_party_id") val selectedPartyId: String,
+    ) : CallEventContent {
+        override val relatesTo: RelatesTo? = null
+        override val mentions: Mentions? = null
+        override val externalUrl: String? = null
+    }
+
+    // Added in V1.11:
+
+    /**
+     * Matrix call SDP stream metadata changed event content
+     *
+     * @see <a href="https://spec.matrix.org/v1.11/client-server-api/#mcallsdp_stream_metadata_changed">matrix spec</a>
+     */
+    @Serializable
+    data class SdpStreamMetadataChanged(
+        @EncodeDefault
+        @Serializable(with = VersionSerializer::class)
+        @SerialName("version") override val version: String = "1",
+        @SerialName("call_id") override val callId: String,
+        @SerialName("party_id") override val partyId: String,
+        @SerialName("sdp_stream_metadata") val sdpStreamMetadata: Map<String, StreamMetadata>,
+    ) : CallEventContent {
+        override val relatesTo: RelatesTo? = null
+        override val mentions: Mentions? = null
+        override val externalUrl: String? = null
+    }
+}
+
+internal object VersionSerializer : KSerializer<String> {
+    override val descriptor: SerialDescriptor = buildClassSerialDescriptor("net.folivo.trixnity.core.model.call.Version")
+
+    override fun deserialize(decoder: Decoder): String {
+        val jsonDecoder = decoder as? JsonDecoder ?: throw IllegalStateException("Expected JsonDecoder")
+        val element = jsonDecoder.decodeJsonElement().jsonPrimitive
+
+        // All VoIP events have a version field. This is used to determine whether devices support this new version of
+        // the protocol. For example, clients can use this field to know whether to expect an m.call.select_answer event
+        // from their opponent. If clients see events with version other than 0 or "1" (including, for example, the
+        // numeric value 1), they should treat these the same as if they had version == "1".
+        // @see <a href="https://spec.matrix.org/v1.10/client-server-api/#voice-over-ip">matrix spec</a>
+        return element.content
+    }
+
+    override fun serialize(encoder: kotlinx.serialization.encoding.Encoder, value: String) {
+        when (value) {
+            "0" -> encoder.encodeLong(0)
+            else -> encoder.encodeString(value)
+        }
+    }
+}
diff --git a/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/m/call/StreamMetadata.kt b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/m/call/StreamMetadata.kt
new file mode 100644
index 0000000000000000000000000000000000000000..b40561a16251243edd5ed55d59bc5f1a82ed9863
--- /dev/null
+++ b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/m/call/StreamMetadata.kt
@@ -0,0 +1,21 @@
+package net.folivo.trixnity.core.model.events.m.call
+
+import kotlinx.serialization.EncodeDefault
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+@Serializable
+enum class Purpose {
+    @SerialName("m.usermedia") USERMEDIA,
+    @SerialName("m.screenshare") SCREENSHARE,
+}
+
+@Serializable
+data class StreamMetadata(
+    @SerialName("purpose") val purpose: Purpose,
+
+    // Added in v1.11:
+
+    @SerialName("audio_muted") val audioMuted: Boolean? = false,
+    @SerialName("video_muted") val videoMuted: Boolean? = false,
+)
diff --git a/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/m/room/RoomMessageEventContent.kt b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/m/room/RoomMessageEventContent.kt
index 4a19f600579e10d619ea878ddd5a7d5edbf9ae89..2a81464093d95727887a96aeb248cb4c25dbf87a 100644
--- a/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/m/room/RoomMessageEventContent.kt
+++ b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/model/events/m/room/RoomMessageEventContent.kt
@@ -18,6 +18,9 @@ import net.folivo.trixnity.core.model.events.m.room.RoomMessageEventContent.*
 import net.folivo.trixnity.core.model.events.m.key.verification.VerificationRequest as IVerificationRequest
 
 /**
+ * Matrix room message event content
+ *
+ * Room messages have "type": "m.room.message".
  * @see <a href="https://spec.matrix.org/v1.10/client-server-api/#mroommessage">matrix spec</a>
  */
 @Serializable(with = RoomMessageEventContentSerializer::class)
diff --git a/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/serialization/events/DefaultEventContentSerializerMappings.kt b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/serialization/events/DefaultEventContentSerializerMappings.kt
index 7d5baf81d58f76a12d158c69a202028080b587c4..18e3f6339c27fcb51a6deff02f9662806c584b1e 100644
--- a/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/serialization/events/DefaultEventContentSerializerMappings.kt
+++ b/trixnity-core/src/commonMain/kotlin/net/folivo/trixnity/core/serialization/events/DefaultEventContentSerializerMappings.kt
@@ -1,6 +1,7 @@
 package net.folivo.trixnity.core.serialization.events
 
 import net.folivo.trixnity.core.model.events.m.*
+import net.folivo.trixnity.core.model.events.m.call.CallEventContent
 import net.folivo.trixnity.core.model.events.m.crosssigning.MasterKeyEventContent
 import net.folivo.trixnity.core.model.events.m.crosssigning.SelfSigningKeyEventContent
 import net.folivo.trixnity.core.model.events.m.crosssigning.UserSigningKeyEventContent
@@ -28,6 +29,14 @@ val DefaultEventContentSerializerMappings = createEventContentSerializerMappings
     messageOf<SasAcceptEventContent>("m.key.verification.accept")
     messageOf<SasKeyEventContent>("m.key.verification.key")
     messageOf<SasMacEventContent>("m.key.verification.mac")
+    messageOf<CallEventContent.Invite>("m.call.invite")
+    messageOf<CallEventContent.Candidates>("m.call.candidates")
+    messageOf<CallEventContent.Answer>("m.call.answer")
+    messageOf<CallEventContent.Hangup>("m.call.hangup")
+    messageOf<CallEventContent.Negotiate>("m.call.negotiate")
+    messageOf<CallEventContent.Reject>("m.call.reject")
+    messageOf<CallEventContent.SelectAnswer>("m.call.select_answer")
+    messageOf<CallEventContent.SdpStreamMetadataChanged>("m.call.sdp_stream_metadata_changed")
 
     stateOf<AvatarEventContent>("m.room.avatar")
     stateOf<CanonicalAliasEventContent>("m.room.canonical_alias")
@@ -84,4 +93,4 @@ val DefaultEventContentSerializerMappings = createEventContentSerializerMappings
     roomAccountDataOf<FullyReadEventContent>("m.fully_read")
     roomAccountDataOf<MarkedUnreadEventContent>("m.marked_unread")
     roomAccountDataOf<TagEventContent>("m.tag")
-}
\ No newline at end of file
+}
diff --git a/trixnity-core/src/commonTest/kotlin/net/folivo/trixnity/core/serialization/m/call/CallEventContentSerializerTest.kt b/trixnity-core/src/commonTest/kotlin/net/folivo/trixnity/core/serialization/m/call/CallEventContentSerializerTest.kt
new file mode 100644
index 0000000000000000000000000000000000000000..e4cda559aa8222918dadec7dab71270f457a1086
--- /dev/null
+++ b/trixnity-core/src/commonTest/kotlin/net/folivo/trixnity/core/serialization/m/call/CallEventContentSerializerTest.kt
@@ -0,0 +1,305 @@
+package net.folivo.trixnity.core.serialization.m.call
+
+import kotlinx.serialization.encodeToString
+import net.folivo.trixnity.core.model.events.m.call.CallEventContent
+import net.folivo.trixnity.core.model.events.m.call.CallEventContent.Answer.Answer
+import net.folivo.trixnity.core.model.events.m.call.CallEventContent.Answer.AnswerType
+import net.folivo.trixnity.core.model.events.m.call.CallEventContent.Candidates.Candidate
+import net.folivo.trixnity.core.model.events.m.call.CallEventContent.Invite.Offer
+import net.folivo.trixnity.core.model.events.m.call.CallEventContent.Invite.OfferType
+import net.folivo.trixnity.core.model.events.m.call.CallEventContent.Hangup.Reason
+import net.folivo.trixnity.core.model.events.m.call.CallEventContent.Negotiate.Description
+import net.folivo.trixnity.core.model.events.m.call.CallEventContent.Negotiate.DescriptionType
+import net.folivo.trixnity.core.model.events.m.call.Purpose
+import net.folivo.trixnity.core.model.events.m.call.StreamMetadata
+import net.folivo.trixnity.core.serialization.createMatrixEventJson
+import net.folivo.trixnity.core.serialization.trimToFlatJson
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class CallEventContentSerializerTest {
+
+    private val json = createMatrixEventJson()
+
+    ////////////////// m.call.invite //////////////////
+
+    private val testInvite = CallEventContent.Invite(
+        version = "1",
+        callId = "0123",
+        offer = Offer(sdp = """
+            v=0
+            o=- 6584580628695956864 2 IN IP4 127.0.0.1
+            """.trimIndent(),
+            type = OfferType.OFFER),
+        lifetime = 30000,
+        sdpStreamMetadata = mapOf(
+            "271828182845" to StreamMetadata(Purpose.SCREENSHARE),
+            "314159265358" to StreamMetadata(Purpose.USERMEDIA),
+        )
+    )
+
+    private val serializedInvite = """{
+        "version": "1",
+        "call_id": "0123",
+        "lifetime": 30000,
+        "offer": {
+            "sdp": "v=0\no=- 6584580628695956864 2 IN IP4 127.0.0.1",
+            "type": "offer"
+        },
+        "sdp_stream_metadata": {
+            "271828182845": {
+                "purpose": "m.screenshare",
+                "audio_muted": false,
+                "video_muted": false
+            },
+            "314159265358": {
+                "purpose": "m.usermedia",
+                "audio_muted": false,
+                "video_muted": false
+            }
+        }
+    }""".trimToFlatJson()
+
+    @Test
+    fun shouldSerializeCallInvite() {
+        val result = json.encodeToString(testInvite)
+        assertEquals(serializedInvite, result)
+    }
+
+    @Test
+    fun shouldDeserializeCallInvite() {
+        val result: CallEventContent.Invite = json.decodeFromString(serializedInvite)
+        assertEquals(testInvite, result)
+    }
+
+    ////////////////// m.call.candidates //////////////////
+
+    private val testCandidates = CallEventContent.Candidates(
+        version = "0",
+        callId = "0123",
+        candidates = listOf(
+            Candidate(
+                candidate = "candidate:423458654 1 udp 2130706431 192.168.0.100 51008 typ host generation 0 ufrag 3f8a",
+                sdpMid = "audio",
+                sdpMLineIndex = 0
+            ),
+            Candidate(
+                candidate = "candidate:423458654 2 udp 2130706431 192.168.0.100 51009 typ host generation 0 ufrag 4839",
+                sdpMid = "audio",
+                sdpMLineIndex = 1
+            ),
+        ),
+    )
+
+    private val serializedCandidates = """{
+        "version": 0,
+        "call_id": "0123",
+        "candidates": [
+            {"candidate":"candidate:423458654 1 udp 2130706431 192.168.0.100 51008 typ host generation 0 ufrag 3f8a","sdpMLineIndex":0,"sdpMid":"audio"},
+            {"candidate":"candidate:423458654 2 udp 2130706431 192.168.0.100 51009 typ host generation 0 ufrag 4839","sdpMLineIndex":1,"sdpMid":"audio"}
+        ]
+    }""".trimToFlatJson()
+
+    @Test
+    fun shouldSerializeCallCandidates() {
+        val result = json.encodeToString(testCandidates)
+        assertEquals(serializedCandidates, result)
+    }
+
+    @Test
+    fun shouldDeserializeCallCandidates() {
+        val result: CallEventContent.Candidates = json.decodeFromString(serializedCandidates)
+        assertEquals(testCandidates, result)
+    }
+
+    ////////////////// m.call.answer //////////////////
+
+    private val testAnswer = CallEventContent.Answer(
+        version = "0",
+        callId = "0123",
+        partyId = null,
+        answer = Answer(sdp = "v=0", type = AnswerType.ANSWER),
+        sdpStreamMetadata = null,
+    )
+    private val serializedAnswer = """{
+        "version": 0,
+        "call_id": "0123",
+        "answer": {"sdp":"v=0","type":"answer"}
+    }""".trimToFlatJson()
+
+    @Test
+    fun shouldSerializeCallAnswer() {
+        val result = json.encodeToString(testAnswer)
+        assertEquals(serializedAnswer, result)
+    }
+
+    @Test
+    fun shouldDeserializeCallAnswer() {
+        val result: CallEventContent.Answer = json.decodeFromString(serializedAnswer)
+        assertEquals(testAnswer, result)
+    }
+
+    ////////////////// m.call.hangup //////////////////
+
+    private val testHangup = CallEventContent.Hangup(
+        callId = "0123",
+        version = "0",
+        partyId = null,
+        reason = Reason.INVITE_TIMEOUT
+    )
+
+    private val serializedHangup = """{
+        "version": 0,
+        "call_id": "0123",
+        "reason": "invite_timeout"
+    }""".trimToFlatJson()
+
+    @Test
+    fun shouldSerializeCallHangup() {
+        val result = json.encodeToString(testHangup)
+        assertEquals(serializedHangup, result)
+    }
+
+    @Test
+    fun shouldDeserializeCallHangup() {
+        val result: CallEventContent.Hangup = json.decodeFromString(serializedHangup)
+        assertEquals(testHangup, result)
+    }
+
+    ////////////////// m.call.negotiate //////////////////
+
+    private val testNegotiate = CallEventContent.Negotiate(
+        callId = "0123",
+        partyId = "67890",
+        description = Description("v=0", DescriptionType.OFFER),
+        lifetime = 10000,
+        sdpStreamMetadata = mapOf(
+            "271828182845" to StreamMetadata(Purpose.SCREENSHARE),
+            "314159265358" to StreamMetadata(Purpose.USERMEDIA),
+        ),
+    )
+    private val serializedNegotiate = """{
+        "version": "1",
+        "call_id": "0123",
+        "party_id": "67890",
+        "description": {
+            "sdp": "v=0",
+            "type": "offer"
+        },
+        "lifetime": 10000,
+        "sdp_stream_metadata": {
+            "271828182845": {
+                "purpose": "m.screenshare",
+                "audio_muted": false,
+                "video_muted": false
+            },
+            "314159265358": {
+                "purpose": "m.usermedia",
+                "audio_muted": false,
+                "video_muted": false
+            }
+        }
+    }""".trimToFlatJson()
+
+    @Test
+    fun shouldSerializeCallNegotiate() {
+        val result = json.encodeToString(testNegotiate)
+        assertEquals(serializedNegotiate, result)
+    }
+
+    @Test
+    fun shouldDeserializeCallNegotiate() {
+        val result: CallEventContent.Negotiate = json.decodeFromString(serializedNegotiate)
+        assertEquals(testNegotiate, result)
+    }
+
+    ////////////////// m.call.reject //////////////////
+
+    private val testReject = CallEventContent.Reject(callId = "0123", partyId = "23423")
+
+    private val serializedReject = """{
+        "version": "1",
+        "call_id": "0123",
+        "party_id": "23423"
+    }""".trimToFlatJson()
+
+    @Test
+    fun shouldSerializeCallReject() {
+        val result = json.encodeToString(testReject)
+        assertEquals(serializedReject, result)
+    }
+
+    @Test
+    fun shouldDeserializeCallReject() {
+        val result: CallEventContent.Reject = json.decodeFromString(serializedReject)
+        assertEquals(testReject, result)
+    }
+
+    ////////////////// m.call.select_answer //////////////////
+
+    private val testSelectAnswer = CallEventContent.SelectAnswer(
+        version = "0",
+        callId = "0123",
+        partyId = "23423",
+        selectedPartyId = "67890"
+    )
+
+    private val serializedSelectAnswer = """{
+        "version": 0,
+        "call_id": "0123",
+        "party_id": "23423",
+        "selected_party_id": "67890"
+    }""".trimToFlatJson()
+
+    @Test
+    fun shouldSerializeCallSelectAnswer() {
+        val result = json.encodeToString(testSelectAnswer)
+        assertEquals(serializedSelectAnswer, result)
+    }
+
+    @Test
+    fun shouldDeserializeCallSelectAnswer() {
+        val result: CallEventContent.SelectAnswer = json.decodeFromString(serializedSelectAnswer)
+        assertEquals(testSelectAnswer, result)
+    }
+
+    ////////////////// m.call.sdp_stream_metadata_changed //////////////////
+
+    private val testSdpStreamMetadataChanged = CallEventContent.SdpStreamMetadataChanged(
+        callId = "0123",
+        partyId = "67890",
+        sdpStreamMetadata = mapOf(
+            "271828182845" to StreamMetadata(Purpose.SCREENSHARE, audioMuted = true),
+            "314159265358" to StreamMetadata(Purpose.USERMEDIA, videoMuted = true),
+        ),
+    )
+    private val serializedSdpStreamMetadataChanged = """{
+        "version": "1",
+        "call_id": "0123",
+        "party_id": "67890",
+        "sdp_stream_metadata": {
+            "271828182845": {
+                "purpose": "m.screenshare",
+                "audio_muted": true,
+                "video_muted": false
+            },
+            "314159265358": {
+                "purpose": "m.usermedia",
+                "audio_muted": false,
+                "video_muted": true
+            }
+        }
+    }""".trimToFlatJson()
+
+    @Test
+    fun shouldDeserializeSdpStreamMetadataChanged() {
+        val result: CallEventContent.SdpStreamMetadataChanged = json.decodeFromString(serializedSdpStreamMetadataChanged)
+        assertEquals(testSdpStreamMetadataChanged, result)
+    }
+
+    @Test
+    fun shouldSerializeSdpStreamMetadataChanged() {
+        val result = json.encodeToString(testSdpStreamMetadataChanged)
+        assertEquals(serializedSdpStreamMetadataChanged, result)
+    }
+}