diff --git a/Cargo.toml b/Cargo.toml
index f78bc3c..0cd39d8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,11 +5,12 @@ members = [
     "poc001",
     "poc002",
     "poc003",
+    "poc004",
 ]
 resolver = "3"
 
 [workspace.package]
-version = "0.3.0"
+version = "0.4.0"
 edition = "2024"
 license = "MIT"
 repository = "https://git.sasedev.com/Sasedev/poc-qt"
diff --git a/poc002/build.rs b/poc002/build.rs
index bad4202..c745197 100644
--- a/poc002/build.rs
+++ b/poc002/build.rs
@@ -269,7 +269,6 @@ fn main() {
     println!("cargo:rerun-if-changed=build.rs");
     println!("cargo:rerun-if-changed=build_config.default.json");
     println!("cargo:rerun-if-changed=build_config.schema.json");
-    println!("cargo:rerun-if-changed=src/bridge.rs");
     println!("cargo:rerun-if-changed=qml/main.qml");
 
     let config_path = PathBuf::from("build_config.json");
diff --git a/poc003/build.rs b/poc003/build.rs
index 88a7df6..8e2001c 100644
--- a/poc003/build.rs
+++ b/poc003/build.rs
@@ -269,7 +269,6 @@ fn main() {
     println!("cargo:rerun-if-changed=build.rs");
     println!("cargo:rerun-if-changed=build_config.default.json");
     println!("cargo:rerun-if-changed=build_config.schema.json");
-    println!("cargo:rerun-if-changed=src/bridge.rs");
     println!("cargo:rerun-if-changed=qml/main.qml");
 
     let config_path = PathBuf::from("build_config.json");
diff --git a/poc004/Cargo.toml b/poc004/Cargo.toml
new file mode 100644
index 0000000..c17670d
--- /dev/null
+++ b/poc004/Cargo.toml
@@ -0,0 +1,20 @@
+# file: poc-qt/poc004/Cargo.toml
+
+[package]
+name = "poc-qt004"
+version = "0.4.0"
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+
+[build-dependencies]
+cxx-qt-build = { workspace = true, features = ["link_qt_object_files"] }
+jsonschema = { workspace = true, features = [] }
+serde = { workspace = true, features = ["derive"] }
+serde_json = { workspace = true, features = [] }
+
+[dependencies]
+cxx = { workspace = true, features = [] }
+cxx-qt = { workspace = true, features = [] }
+cxx-qt-lib = { workspace = true, features = ["full", "link_qt_object_files"] }
+
diff --git a/poc004/build.rs b/poc004/build.rs
new file mode 100644
index 0000000..faab617
--- /dev/null
+++ b/poc004/build.rs
@@ -0,0 +1,296 @@
+// file: poc-qt/poc004/build.rs
+
+use std::collections::BTreeMap;
+use std::fs;
+use std::path::{Path, PathBuf};
+
+use cxx_qt_build::{CxxQtBuilder, QmlModule};
+use serde::Deserialize;
+use serde_json::Value;
+
+const DEFAULT_CONFIG_STR: &str = include_str!("build_config.default.json");
+const CONFIG_SCHEMA_STR: &str = include_str!("../build_config.schema.json");
+
+#[derive(Debug, Deserialize)]
+struct BuildConfig {
+    active_profile: String,
+    profiles: BTreeMap<String, BuildProfile>,
+}
+
+#[derive(Debug, Deserialize)]
+struct BuildProfile {
+    qt: QtConfig,
+    link: LinkConfig,
+}
+
+#[derive(Debug, Deserialize)]
+struct QtConfig {
+    qmake: String,
+    lib_dir: String,
+    qml_dir: String,
+    plugins_dir: String,
+    version_major: u8,
+}
+
+#[derive(Debug, Deserialize)]
+struct LinkConfig {
+    rpaths: Vec<String>,
+}
+
+fn ensure_user_config_exists(config_path: &Path) {
+    if config_path.exists() {
+        return;
+    }
+
+    match fs::write(config_path, DEFAULT_CONFIG_STR) {
+        Ok(()) => {
+            println!(
+                "cargo:warning=build_config.json was missing and has been created from build_config.default.json"
+            );
+        }
+        Err(err) => {
+            panic!(
+                "failed to create {} from embedded defaults: {}",
+                config_path.display(),
+                err
+            );
+        }
+    }
+}
+
+fn validate_embedded_schema() {
+    let schema_json = parse_json_str(CONFIG_SCHEMA_STR, "embedded build_config.schema.json");
+
+    match jsonschema::meta::validate(&schema_json) {
+        Ok(()) => {}
+        Err(err) => {
+            panic!("embedded build_config.schema.json is not a valid JSON Schema: {err}");
+        }
+    }
+}
+
+fn validate_default_config() {
+    validate_config_str_against_schema(DEFAULT_CONFIG_STR, "embedded build_config.default.json");
+}
+
+fn validate_user_config(config_path: &Path) {
+    let raw = match fs::read_to_string(config_path) {
+        Ok(v) => v,
+        Err(err) => {
+            panic!("failed to read {}: {}", config_path.display(), err);
+        }
+    };
+
+    validate_config_str_against_schema(&raw, &format!("{}", config_path.display()));
+}
+
+fn validate_config_str_against_schema(config_raw: &str, config_name: &str) {
+    let schema_json = parse_json_str(CONFIG_SCHEMA_STR, "embedded build_config.schema.json");
+    let config_json = parse_json_str(config_raw, config_name);
+
+    let validator = match jsonschema::validator_for(&schema_json) {
+        Ok(v) => v,
+        Err(err) => {
+            panic!(
+                "failed to build JSON Schema validator for {}: {}",
+                config_name, err
+            );
+        }
+    };
+
+    if validator.is_valid(&config_json) {
+        return;
+    }
+
+    let mut errors = Vec::new();
+    for err in validator.iter_errors(&config_json) {
+        errors.push(format!(
+            "- {} at instance path {}",
+            err,
+            err.instance_path()
+        ));
+    }
+
+    let joined = errors.join("\n");
+    panic!("{} failed schema validation:\n{}", config_name, joined);
+}
+
+fn load_build_config(config_path: &Path) -> BuildConfig {
+    let raw = match fs::read_to_string(config_path) {
+        Ok(v) => v,
+        Err(err) => {
+            panic!("failed to read {}: {}", config_path.display(), err);
+        }
+    };
+
+    match serde_json::from_str::<BuildConfig>(&raw) {
+        Ok(v) => v,
+        Err(err) => {
+            panic!(
+                "failed to deserialize {} into BuildConfig: {}",
+                config_path.display(),
+                err
+            );
+        }
+    }
+}
+
+fn resolve_profile_name(build_config: &BuildConfig) -> String {
+    let env_profile = std::env::var("BUILD_CONFIG_PROFILE");
+    match env_profile {
+        Ok(v) => {
+            if v.trim().is_empty() {
+                build_config.active_profile.clone()
+            } else {
+                v
+            }
+        }
+        Err(_) => build_config.active_profile.clone(),
+    }
+}
+
+fn resolve_profile<'a>(build_config: &'a BuildConfig, profile_name: &str) -> &'a BuildProfile {
+    match build_config.profiles.get(profile_name) {
+        Some(v) => v,
+        None => {
+            let mut available = Vec::new();
+            for key in build_config.profiles.keys() {
+                available.push(key.clone());
+            }
+            panic!(
+                "active profile '{}' not found in build_config.json. available profiles: {}",
+                profile_name,
+                available.join(", ")
+            );
+        }
+    }
+}
+
+fn validate_profile_paths(profile: &BuildProfile, profile_name: &str) {
+    ensure_existing_file(&profile.qt.qmake, profile_name, "qt.qmake");
+    ensure_existing_dir(&profile.qt.lib_dir, profile_name, "qt.lib_dir");
+    ensure_existing_dir(&profile.qt.qml_dir, profile_name, "qt.qml_dir");
+    ensure_existing_dir(&profile.qt.plugins_dir, profile_name, "qt.plugins_dir");
+
+    let mut index = 0usize;
+    while index < profile.link.rpaths.len() {
+        ensure_existing_dir(
+            &profile.link.rpaths[index],
+            profile_name,
+            &format!("link.rpaths[{index}]"),
+        );
+        index += 1;
+    }
+}
+
+fn ensure_existing_file(path_str: &str, profile_name: &str, field_name: &str) {
+    let path = Path::new(path_str);
+    if !path.exists() {
+        panic!(
+            "profile '{}' has invalid {}: path does not exist: {}",
+            profile_name,
+            field_name,
+            path.display()
+        );
+    }
+    if !path.is_file() {
+        panic!(
+            "profile '{}' has invalid {}: path is not a file: {}",
+            profile_name,
+            field_name,
+            path.display()
+        );
+    }
+}
+
+fn ensure_existing_dir(path_str: &str, profile_name: &str, field_name: &str) {
+    let path = Path::new(path_str);
+    if !path.exists() {
+        panic!(
+            "profile '{}' has invalid {}: path does not exist: {}",
+            profile_name,
+            field_name,
+            path.display()
+        );
+    }
+    if !path.is_dir() {
+        panic!(
+            "profile '{}' has invalid {}: path is not a directory: {}",
+            profile_name,
+            field_name,
+            path.display()
+        );
+    }
+}
+
+fn apply_build_environment(profile: &BuildProfile) {
+    unsafe {
+        std::env::set_var("QMAKE", &profile.qt.qmake);
+        std::env::set_var("QT_VERSION_MAJOR", profile.qt.version_major.to_string());
+    }
+
+    println!("cargo:rerun-if-env-changed=BUILD_CONFIG_PROFILE");
+    println!("cargo:rerun-if-env-changed=QMAKE");
+    println!("cargo:rerun-if-env-changed=QT_VERSION_MAJOR");
+}
+
+fn apply_linker_settings(profile: &BuildProfile) {
+    let mut index = 0usize;
+    while index < profile.link.rpaths.len() {
+        println!(
+            "cargo:rustc-link-arg=-Wl,-rpath,{}",
+            profile.link.rpaths[index]
+        );
+        index += 1;
+    }
+}
+
+fn emit_runtime_hints(profile: &BuildProfile, profile_name: &str) {
+    println!(
+        "cargo:warning=using build profile '{}' with qmake '{}'",
+        profile_name, profile.qt.qmake
+    );
+    println!(
+        "cargo:warning=qt lib_dir='{}', qml_dir='{}', plugins_dir='{}'",
+        profile.qt.lib_dir, profile.qt.qml_dir, profile.qt.plugins_dir
+    );
+}
+
+fn parse_json_str(raw: &str, label: &str) -> Value {
+    match serde_json::from_str::<Value>(raw) {
+        Ok(v) => v,
+        Err(err) => {
+            panic!("failed to parse {} as JSON: {}", label, err);
+        }
+    }
+}
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-changed=build_config.default.json");
+    println!("cargo:rerun-if-changed=build_config.schema.json");
+    println!("cargo:rerun-if-changed=qml/main.qml");
+
+    let config_path = PathBuf::from("build_config.json");
+
+    ensure_user_config_exists(&config_path);
+    validate_embedded_schema();
+    validate_default_config();
+    validate_user_config(&config_path);
+
+    let build_config = load_build_config(&config_path);
+    let profile_name = resolve_profile_name(&build_config);
+    let profile = resolve_profile(&build_config, &profile_name);
+
+    validate_profile_paths(profile, &profile_name);
+    apply_build_environment(profile);
+    apply_linker_settings(profile);
+
+    CxxQtBuilder::new_qml_module(QmlModule::new("com.sasedev.cam02").qml_files(["qml/main.qml"]))
+        .qt_module("Qml")
+        .qt_module("Network")
+        .qt_module("Multimedia")
+        .build();
+
+    emit_runtime_hints(profile, &profile_name);
+}
diff --git a/poc004/build_config.default.json b/poc004/build_config.default.json
new file mode 100644
index 0000000..6a31de4
--- /dev/null
+++ b/poc004/build_config.default.json
@@ -0,0 +1,33 @@
+{
+    "active_profile": "sinus",
+    "profiles": {
+        "sinus": {
+            "qt": {
+                "qmake": "/home/sinus/DEV/Qt/6.11.0/gcc_64/bin/qmake",
+                "lib_dir": "/home/sinus/DEV/Qt/6.11.0/gcc_64/lib",
+                "qml_dir": "/home/sinus/DEV/Qt/6.11.0/gcc_64/qml",
+                "plugins_dir": "/home/sinus/DEV/Qt/6.11.0/gcc_64/plugins",
+                "version_major": 6
+            },
+            "link": {
+                "rpaths": [
+                    "/home/sinus/DEV/Qt/6.11.0/gcc_64/lib"
+                ]
+            }
+        },
+        "system": {
+            "qt": {
+                "qmake": "/usr/bin/qmake6",
+                "lib_dir": "/usr/lib/x86_64-linux-gnu",
+                "qml_dir": "/usr/lib/x86_64-linux-gnu/qt6/qml",
+                "plugins_dir": "/usr/lib/x86_64-linux-gnu/qt6/plugins",
+                "version_major": 6
+            },
+            "link": {
+                "rpaths": [
+                    "/usr/lib/x86_64-linux-gnu"
+                ]
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/poc004/qml/main.qml b/poc004/qml/main.qml
new file mode 100644
index 0000000..2081223
--- /dev/null
+++ b/poc004/qml/main.qml
@@ -0,0 +1,188 @@
+// file: poc-qt/poc004/qml/main.qml
+
+import QtQuick
+import QtQuick.Controls
+import QtQuick.Layouts
+import QtMultimedia
+
+ApplicationWindow {
+    visible: true
+    width: 1100
+    height: 760
+    title: "POC004 - Webcam + Micro + Capture + Record"
+
+    MediaDevices {
+        id: mediaDevices
+    }
+
+    Camera {
+        id: camera
+        cameraDevice: mediaDevices.defaultVideoInput
+    }
+
+    AudioInput {
+        id: microphone
+    }
+
+    ImageCapture {
+        id: imageCapture
+        onImageSaved: function(requestId, filePath) {
+            statusLabel.text = "Image saved: " + filePath
+        }
+        onErrorOccurred: function(requestId, error, errorString) {
+            statusLabel.text = "Image error: " + errorString
+        }
+    }
+
+    MediaRecorder {
+        id: recorder
+        quality: MediaRecorder.VeryHighQuality
+        onRecorderStateChanged: {
+            if (recorder.recorderState === MediaRecorder.RecordingState) {
+                statusLabel.text = "Recording video..."
+            } else if (recorder.recorderState === MediaRecorder.StoppedState) {
+                statusLabel.text = "Recorder stopped"
+            }
+        }
+        onErrorOccurred: function(error, errorString) {
+            statusLabel.text = "Recorder error: " + errorString
+        }
+    }
+
+    CaptureSession {
+        id: captureSession
+        camera: camera
+        audioInput: microphone
+        imageCapture: imageCapture
+        recorder: recorder
+        videoOutput: videoOutput
+    }
+
+    ColumnLayout {
+        anchors.fill: parent
+        anchors.margins: 12
+        spacing: 10
+
+        Rectangle {
+            Layout.fillWidth: true
+            Layout.fillHeight: true
+            color: "black"
+            border.width: 1
+            border.color: "#555"
+
+            VideoOutput {
+                id: videoOutput
+                anchors.fill: parent
+                fillMode: VideoOutput.PreserveAspectFit
+            }
+        }
+
+        RowLayout {
+            Layout.fillWidth: true
+            spacing: 8
+
+            Button {
+                text: camera.active ? "Stop camera" : "Start camera"
+                onClicked: {
+                    camera.active = !camera.active
+                    if (camera.active) {
+                        statusLabel.text = "Camera started"
+                    } else {
+                        statusLabel.text = "Camera stopped"
+                    }
+                }
+            }
+
+            Button {
+                text: "Take snapshot"
+                onClicked: {
+                    imageCapture.captureToFile("/home/sinus/Projects/poc-qt/target/captures_imgs/image_" + Date.now() + ".jpg")
+                }
+            }
+
+            Button {
+                text: recorder.recorderState === MediaRecorder.RecordingState ? "Stop recording" : "Start recording"
+                onClicked: {
+                    if (recorder.recorderState === MediaRecorder.RecordingState) {
+                        recorder.stop()
+                    } else {
+                        recorder.outputLocation = "file:///home/sinus/Projects/poc-qt/target/captures_vids/video_" + Date.now() + ".mp4"
+                        recorder.record()
+                    }
+                }
+            }
+
+            Button {
+                text: "Restart camera"
+                onClicked: {
+                    camera.stop()
+                    camera.start()
+                }
+            }
+        }
+
+        RowLayout {
+            Layout.fillWidth: true
+            spacing: 8
+
+            Label {
+                text: mediaDevices.videoInputs.length > 0
+                    ? ("Camera: " + camera.cameraDevice.description)
+                    : "No camera detected"
+                Layout.fillWidth: true
+                wrapMode: Text.WrapAnywhere
+            }
+
+            Label {
+                text: "Mic active"
+            }
+        }
+
+        Label {
+            id: statusLabel
+            Layout.fillWidth: true
+            text: "Ready"
+            wrapMode: Text.WrapAnywhere
+        }
+
+        ListView {
+            Layout.fillWidth: true
+            Layout.preferredHeight: 120
+            clip: true
+            model: mediaDevices.videoInputs
+
+            delegate: Rectangle {
+                width: ListView.view.width
+                height: 32
+                color: camera.cameraDevice.id === modelData.id ? "#334" : "transparent"
+
+                Text {
+                    anchors.verticalCenter: parent.verticalCenter
+                    anchors.left: parent.left
+                    anchors.leftMargin: 8
+                    text: modelData.description
+                    color: "white"
+                }
+
+                MouseArea {
+                    anchors.fill: parent
+                    onClicked: {
+                        camera.stop()
+                        camera.cameraDevice = modelData
+                        camera.start()
+                        statusLabel.text = "Switched camera to: " + modelData.description
+                    }
+                }
+            }
+        }
+    }
+
+    Component.onCompleted: {
+        if (mediaDevices.videoInputs.length > 0) {
+            camera.start()
+            statusLabel.text = "Camera started"
+        } else {
+            statusLabel.text = "No camera detected"
+        }
+    }
+}
diff --git a/poc004/src/main.rs b/poc004/src/main.rs
new file mode 100644
index 0000000..28790d1
--- /dev/null
+++ b/poc004/src/main.rs
@@ -0,0 +1,54 @@
+// file: poc-qt/poc004/src/main.rs
+
+use cxx_qt_lib::{QGuiApplication, QQmlApplicationEngine, QString, QUrl};
+use std::env;
+use std::path::PathBuf;
+
+fn main() {
+    let mut app = QGuiApplication::new();
+    let mut engine = QQmlApplicationEngine::new();
+
+    let current_dir = match env::current_dir() {
+        Ok(v) => v,
+        Err(err) => {
+            eprintln!("failed to get current_dir: {err}");
+            return;
+        }
+    };
+
+    let main_qml_path: PathBuf = current_dir.join("qml/main.qml");
+    let main_qml_path = match main_qml_path.canonicalize() {
+        Ok(v) => v,
+        Err(err) => {
+            eprintln!(
+                "failed to resolve qml/main.qml from {}: {err}",
+                main_qml_path.display()
+            );
+            return;
+        }
+    };
+
+    let main_qml_str = match main_qml_path.to_str() {
+        Some(v) => v.to_string(),
+        None => {
+            eprintln!("qml path is not valid UTF-8: {}", main_qml_path.display());
+            return;
+        }
+    };
+
+    println!("loading qml from: {}", main_qml_str);
+
+    if let Some(engine_ref) = engine.as_mut() {
+        let qml_url = QUrl::from_local_file(&QString::from(main_qml_str));
+        engine_ref.load(&qml_url);
+    } else {
+        eprintln!("failed to create QQmlApplicationEngine");
+        return;
+    }
+
+    if let Some(app_ref) = app.as_mut() {
+        app_ref.exec();
+    } else {
+        eprintln!("failed to create QGuiApplication");
+    }
+}