Align desktop audio startup with the first decoded video frame

tools/chatgui/tests/test_stream_view.cpp

@@ -187,8 +187,7 @@ private slots:
 #endif
         StreamPlayerWindow window(group, inst->node_id, epoch, "Source");
         QSignalSpy shown(&window, &StreamPlayerWindow::framePresented); window.show();
-        QTimer sender;
-        connect(&sender, &QTimer::timeout, this, [this, video, &opus, &sampleFrame] {
+        auto audioPackets = [&opus, &sampleFrame] {
             QList<QByteArray> packets;
             if (opus) for (unsigned frame = 0; frame < 5; frame++) {
                 int16_t pcm[1920]; uint8_t encoded[1275];
@@ -200,7 +199,18 @@ private slots:
                 int length = opus_codec_encode(opus.get(), pcm, 960, encoded, sizeof(encoded)); QVERIFY(length > 0);
                 packets.append(QByteArray(reinterpret_cast<const char*>(encoded), length));
             }
-            publish(video, packets, 3);
+            return packets;
+        };
+#ifdef TEST_NULL_AUDIO
+        QTest::qWait(20);
+        for (unsigned batch = 0; batch < 8; batch++) { publish({}, audioPackets(), 0); uasync_poll(ua, 0); }
+        QTest::qWait(200);
+        QCOMPARE(shown.count(), 0);
+        QCOMPARE(nonzeroSamples.load(), uint64_t(0));
+#endif
+        QTimer sender;
+        connect(&sender, &QTimer::timeout, this, [this, video, &audioPackets] {
+            publish(video, audioPackets(), 3);
         });
         sender.start(100);
         QTRY_VERIFY_WITH_TIMEOUT(shown.count() > 0, 5000);