Preserve desktop camera cadence under timestamp jitter

tools/chatgui/src/call_video_cadence.h

@@ -0,0 +1,15 @@
+#pragma once
+#include <algorithm>
+#include <cstdint>
+
+// Сетка 30 fps с допуском половины периода: дрожание PTS не превращает 30 fps в 15.
+class CallVideoCadence {
+    int64_t next = -1;
+public:
+    bool accept(int64_t pts) {
+        constexpr int64_t period = 1000000 / 30;
+        if (next >= 0 && pts < next - period / 2) return false;
+        next = next < 0 ? pts + period : std::max(next + period, pts + period / 2);
+        return true;
+    }
+};

tools/chatgui/src/call_video_engine.cpp

@@ -1,6 +1,7 @@
 #include "call_video_engine.h"
 #include "call_video_encoder.h"
 #include "call_video_decoder.h"
+#include "call_video_cadence.h"
 #include "../../../src/call/call_video_port.h"
 #include "../../../src/call/call_audio.h"
 #include "debug_config.h"
@@ -174,7 +175,7 @@ void CallVideoEngine::transmit() {
     int64_t reportAt = nowUs(), encodeMax = 0;
     uint64_t captureBase = 0;
     unsigned encodedCount = 0, keyCount = 0, sendBusy = 0, paced = 0;
-    int64_t pacedPts = -1;
+    CallVideoCadence cadence;
     while (m->running) {
         struct call_video_port_status state{};
         if (call_video_port_status(m->id, &state) < 0) break;
@@ -210,10 +211,6 @@ void CallVideoEngine::transmit() {
         }
         if (format.generation && state.have_peer && !call_video_format_supported(&caps, &state.peer, &format)) appliedRevision = 0;
         if (!enabled || !state.have_peer || pts <= lastPts) { idle(); continue; }
-        if (lastPts >= 0 && pts - lastPts < 33333) {
-            if (pacedPts != pts) { pacedPts = pts; ++paced; }
-            idle(); continue;
-        }
         if (revision != appliedRevision) {
             if (lastKey >= 0 && pts - lastKey < 1000000) { idle(); continue; }
             call_video_format next{format.generation + 1, (uint16_t)width, (uint16_t)height, 30, 0, (uint8_t)codec, 0, 4000000, 0};
@@ -243,6 +240,7 @@ void CallVideoEngine::transmit() {
                 call_video_port_applied(m->id, format.generation, request, 0);
         }
 #ifdef HAVE_STREAM_CAPTURE
+        if (!cadence.accept(pts)) { lastPts = pts; ++paced; idle(); continue; }
         QImage image = raw.toImage();
         if (image.isNull()) { DEBUG_WARN(DEBUG_CATEGORY_CALL, "camera frame conversion failed"); lastPts = pts; continue; }
         LiveEncodedFrame output; CallVideoRateCompletion completion;

tools/chatgui/tests/test_call_video_encoder.cpp

@@ -5,6 +5,7 @@
 #include <clocale>
 #include "../src/call_video_encoder.h"
 #include "../src/call_video_decoder.h"
+#include "../src/call_video_cadence.h"
 #include "../../../src/call/call_video_bitstream.h"
 extern "C" {
 #include "debug_config.h"
@@ -41,6 +42,15 @@ class CallVideoEncoderTest : public QObject {
         return {17, 640, 360, 30, 0, (uint8_t)codec, (uint8_t)(codec == 1 ? 31 : 93), 4000000, (uint8_t)(codec == 1 ? 2 : 1)};
     }
 private slots:
+    void captureCadence() {
+        CallVideoCadence jittered, fast;
+        for (int i = 0; i < 300; i++) QVERIFY(jittered.accept(1000000 + i * 33333 + (i % 2 ? -1500 : 1500)));
+        int accepted = 0;
+        for (int i = 0; i < 600; i++) if (fast.accept(1000000 + i * 1000000LL / 60)) accepted++;
+        QCOMPARE(accepted, 300);
+        QVERIFY(jittered.accept(30000000)); // Долгая пауза не создаёт догоняющий burst.
+        QVERIFY(!jittered.accept(30001000));
+    }
     void initTestCase() {
         debug_config_init(); debug_set_level(DEBUG_LEVEL_WARN); debug_set_category_level(DEBUG_CATEGORY_CALL, DEBUG_LEVEL_DEBUG);
         av_log_set_level(AV_LOG_ERROR);