Sound für synchrone Wiedergabe geändert

include/videowidget.h

@@ -11,6 +11,7 @@
 #include <QProcess>
 
 #include "v4l2worker.h"
+#include "audiothread.h"
 
 // A uniform, icon-only push button used for the video toolbar (start/stop,
 // freeze, screenshot, record, fullscreen, audio, ...). All toolbar buttons
@@ -142,14 +143,12 @@ private:
 
     // Audio passthrough: plays the grabber's ALSA capture device (e.g. the
     // "USB Audio" card that accompanies a /dev/videoN HDMI/USB grabber)
-    // straight to the default output, the same way the HDMI viewer does it.
-    // Implemented by shelling out to `ffplay -f alsa -i <device>` with
-    // -nodisp (audio only, no extra window) - same approach as recording,
-    // just piping the other direction (device -> speakers instead of
-    // frames -> file).
+    // straight to the default output. Uses the same native ALSA
+    // capture->playback thread (AudioThread) as the HDMI viewer, with small
+    // buffers so the sound stays in sync with the video preview.
     QComboBox   *m_audioCombo    = nullptr;
     QPushButton *m_audioBtn      = nullptr;
-    QProcess    *m_audioProcess  = nullptr;
+    AudioThread *m_audioThread   = nullptr;
     bool         m_audioActive   = false;
 
     // Fullscreen overlay window (nullptr when not open). Owns itself via