Prepare and cache desktop video codecs once at application startup

tools/chatgui/src/call_video_engine.cpp

@@ -9,6 +9,7 @@
 #include "../../../src/call/call_audio.h"
 #include "debug_config.h"
 #include "mem.h"
+#include <QThread>
 #include <thread>
 #include <mutex>
 #include <condition_variable>
@@ -252,10 +253,26 @@ void CallVideoEngine::setVideo(bool enabled, const QByteArray& cameraId, int wid
 #endif
 }
 
-void CallVideoEngine::transmit() {
-    call_video_caps caps = CallVideoDecoder::capabilities(&m->running);
+call_video_caps CallVideoEngine::capabilities(const std::atomic<bool>* running) {
+    static std::mutex lock;
+    static call_video_caps verified{};
+    static bool initialized = false;
+    const int64_t started = nowUs();
+    auto cancelled = [running] {
+        if (!running || running->load()) return false;
+        DEBUG_INFO(DEBUG_CATEGORY_CALL, "video codec preparation cancelled; completed cache retained"); return true;
+    };
+    std::unique_lock<std::mutex> guard(lock, std::defer_lock);
+    while (!guard.try_lock()) { if (cancelled()) return {}; QThread::usleep(1000); }
+    if (cancelled()) return {};
+    if (initialized) {
+        DEBUG_INFO(DEBUG_CATEGORY_CALL, "video codec capabilities cache hit wait_us=%lld", (long long)(nowUs() - started));
+        return verified;
+    }
+    DEBUG_INFO(DEBUG_CATEGORY_CALL, "video codec preparation begin; camera and network unused");
+    call_video_caps caps = CallVideoDecoder::capabilities(running);
     // Не связываем приём с наличием собственного encoder.
-    for (unsigned codec = 1; codec <= 2 && m->running; ++codec) {
+    for (unsigned codec = 1; codec <= 2; ++codec) {
         for (const QSize size : {QSize(1920, 1080), QSize(1280, 720)}) {
           for (unsigned fps : {30u, 50u, 60u}) {
             const bool fullhd = size.width() == 1920;
@@ -264,14 +281,15 @@ void CallVideoEngine::transmit() {
                     : (fullhd ? (fps > 30 ? 123 : 120) : (fps > 30 ? 120 : 93))), 4000000,
                 (uint8_t)(codec == 1 ? CALL_VIDEO_CONSTRAINED_BASELINE : CALL_VIDEO_MAIN)};
             bool bothOrientations = true;
-            for (int portrait = 0; portrait <= 1 && bothOrientations && m->running; ++portrait) {
+            for (int portrait = 0; portrait <= 1 && bothOrientations; ++portrait) {
+                if (cancelled()) return {};
                 probe.width = portrait ? size.height() : size.width(); probe.height = portrait ? size.width() : size.height();
                 CallVideoEncoder encoder;
                 bothOrientations = encoder.open(probe, 1000000);
                 if (!bothOrientations) DEBUG_WARN(DEBUG_CATEGORY_CALL, "call codec probe unavailable codec=%u size=%ux%u: %s",
                     codec, probe.width, probe.height, qPrintable(encoder.error()));
             }
-            if (bothOrientations && m->running) {
+            if (bothOrientations) {
                 auto& limit = caps.encode[codec - 1];
                 limit.width = std::max<int>(limit.width, size.width()); limit.height = std::max<int>(limit.height, size.height());
                 limit.fps = std::max<unsigned>(limit.fps, fps);
@@ -284,6 +302,16 @@ void CallVideoEngine::transmit() {
         }
         if (caps.encode[codec - 1].profiles && call_video_limit_orientations(&caps.encode[codec - 1], codec)) caps.encode[codec - 1] = {};
     }
+    if (cancelled()) return {};
+    verified = caps; initialized = true;
+    DEBUG_INFO(DEBUG_CATEGORY_CALL, "video codec preparation complete elapsed_us=%lld encode=%u/%u decode=%u/%u",
+        (long long)(nowUs() - started), caps.encode[0].profiles, caps.encode[1].profiles,
+        caps.decode[0].profiles, caps.decode[1].profiles);
+    return verified;
+}
+
+void CallVideoEngine::transmit() {
+    const call_video_caps caps = capabilities(&m->running);
     if (!m->running) return;
     if (call_video_port_open(m->id, &caps) < 0) { m->report(tr("Video transport is unavailable")); return; }
     CallVideoEncoder encoder;