diff --git a/tools/chatgui/src/call_video_engine.cpp b/tools/chatgui/src/call_video_engine.cpp
index f69675e9..469d379e 100644
--- a/tools/chatgui/src/call_video_engine.cpp
+++ b/tools/chatgui/src/call_video_engine.cpp
@@ -35,7 +35,8 @@ struct CallVideoEngine::Impl {
     uint64_t captured = 0;
     QImage shown;
     uint64_t shownSerial = 0, deliveredSerial = 0;
-    int64_t previewPts = -1, previewAt = 0;
+    int64_t previewPts = -1, previewReportAt = 0, previewMaxUs = 0;
+    unsigned previewFrames = 0;
     bool previewVisible = false;
     QString status;
     bool statusDirty = false;
@@ -52,6 +53,7 @@ struct CallVideoEngine::Impl {
 };
 CallVideoEngine::CallVideoEngine(QObject* parent) : QObject(parent), m(std::make_unique<Impl>()) {
     m_timer.setInterval(20);
+    m_timer.setTimerType(Qt::PreciseTimer);
     connect(&m_timer, &QTimer::timeout, this, [this] {
         QImage image; QString status; bool changed = false, report = false;
         { std::lock_guard<std::mutex> guard(m->lock);
@@ -64,8 +66,8 @@ CallVideoEngine::CallVideoEngine(QObject* parent) : QObject(parent), m(std::make
         int64_t now = nowUs();
         { std::lock_guard<std::mutex> guard(m->lock);
           if (!m->enabled && m->previewVisible) { m->previewVisible = false; clear = true; }
-          if (m->enabled && m->raw.isValid() && m->pts != m->previewPts && now - m->previewAt >= 100000) {
-              preview = m->raw; m->previewPts = m->pts; m->previewAt = now;
+          if (m->enabled && m->raw.isValid() && m->pts != m->previewPts) {
+              preview = m->raw; m->previewPts = m->pts;
           } }
         if (clear) emit localImageChanged({});
         if (preview.isValid()) {
@@ -73,8 +75,15 @@ CallVideoEngine::CallVideoEngine(QObject* parent) : QObject(parent), m(std::make
             if (!local.isNull()) {
                 m->previewVisible = true;
                 emit localImageChanged(local.scaled(320, 240, Qt::KeepAspectRatio, Qt::SmoothTransformation));
+                ++m->previewFrames;
+                m->previewMaxUs = std::max(m->previewMaxUs, nowUs() - now);
             } else DEBUG_WARN(DEBUG_CATEGORY_CALL, "call camera preview conversion failed");
         }
+        if (m->previewVisible && now - m->previewReportAt >= 1000000) {
+            DEBUG_DEBUG(DEBUG_CATEGORY_CALL, "video local preview call=%llu interval_us=%lld frames=%u update_max_us=%lld",
+                (unsigned long long)m->id, (long long)(now - m->previewReportAt), m->previewFrames, (long long)m->previewMaxUs);
+            m->previewReportAt = now; m->previewFrames = 0; m->previewMaxUs = 0;
+        }
 #endif
     });
 }
@@ -99,7 +108,8 @@ void CallVideoEngine::closeCamera() {
     m->capture.reset(); m->camera.reset(); m->sink.reset();
     { std::lock_guard<std::mutex> guard(m->lock); m->raw = {}; m->pts = m->backend = m->anchor = -1; }
 #endif
-    m->previewPts = -1; m->previewVisible = false; emit localImageChanged({});
+    m->previewPts = -1; m->previewVisible = false; m->previewReportAt = nowUs(); m->previewFrames = 0; m->previewMaxUs = 0;
+    emit localImageChanged({});
 }
 void CallVideoEngine::stop() {
     m->running = false; m_timer.stop(); closeCamera();
@@ -127,6 +137,10 @@ void CallVideoEngine::setVideo(bool enabled, const QByteArray& cameraId, int wid
         if (score < distance) { best = f; distance = score; }
     }
     if (!best.isNull()) m->camera->setCameraFormat(best);
+    const auto selectedFormat = m->camera->cameraFormat();
+    DEBUG_INFO(DEBUG_CATEGORY_CALL, "call camera selected device=%s size=%dx%d pixel=%d fps=%.3f..%.3f",
+        selected.id().constData(), selectedFormat.resolution().width(), selectedFormat.resolution().height(),
+        selectedFormat.pixelFormat(), selectedFormat.minFrameRate(), selectedFormat.maxFrameRate());
     connect(m->sink.get(), &QVideoSink::videoFrameChanged, this, [this, revision](const QVideoFrame& frame) {
         if (!frame.isValid() || !m->running) return;
         std::lock_guard<std::mutex> guard(m->lock);