Incorporating VideoCacheThread into openshot-example executable, to experiment with caching during export. It works great!

examples/Example.cpp

@@ -1,12 +1,12 @@
 /**
  * @file
- * @brief Source file for Example Executable (example app for libopenshot)
+ * @brief Example application showing how to attach VideoCacheThread to an FFmpegReader
  * @author Jonathan Thomas <jonathan@openshot.org>
  *
  * @ref License
  */
 
-// Copyright (c) 2008-2019 OpenShot Studios, LLC
+// Copyright (c) 2008-2025 OpenShot Studios, LLC
 //
 // SPDX-License-Identifier: LGPL-3.0-or-later
 
@@ -16,62 +16,80 @@
 #include "Frame.h"
 #include "FFmpegReader.h"
 #include "FFmpegWriter.h"
+#include "Timeline.h"
+#include "Qt/VideoCacheThread.h"    // <— your new header
 
 using namespace openshot;
 
 int main(int argc, char* argv[]) {
-    // Path to your video
-    const char* path = "/home/jonathan/Downloads/openshot-testing/sintel_trailer-720p.mp4";
-
-    FFmpegReader r(path);
-    r.Open();
-
-    const long int total_frames = r.info.video_length;
 
 
-    // Reader
-    std::stringstream writer_path;
-    writer_path << TEST_MEDIA_PATH << "sintel_trailer-720p.mp4";
+    // 1) Open the FFmpegReader as usual
+    const char* input_path = "/home/jonathan/Downloads/openshot-testing/sintel_trailer-720p.mp4";
+    FFmpegReader reader(input_path);
+    reader.Open();
 
-    /* WRITER ---------------- */
-    FFmpegWriter w("/home/jonathan/Downloads/performance-test.mp4");
-
-    // Set options
-    w.SetAudioOptions("aac", 48000, 192000);
-    w.SetVideoOptions("libx264", 1280, 720, Fraction(30,1), 5000000);
-
-    // Open writer
-    w.Open();
+    const int64_t total_frames = reader.info.video_length;
+    std::cout << "Total frames: " << total_frames << "\n";
 
 
-    // --- Measure forward pass ---
+
+    Timeline timeline(reader.info.width, reader.info.height, reader.info.fps, reader.info.sample_rate, reader.info.channels, reader.info.channel_layout);
+    Clip c1(&reader);
+    timeline.AddClip(&c1);
+    timeline.Open();
+    timeline.DisplayInfo();
+
+
+    // 2) Construct a VideoCacheThread around 'reader' and start its background loop
+    //    (VideoCacheThread inherits juce::Thread)
+    std::shared_ptr<VideoCacheThread> cache = std::make_shared<VideoCacheThread>();
+    cache->Reader(&timeline);    // attaches the FFmpegReader and internally calls Play()
+    cache->StartThread();      // juce::Thread method, begins run()
+
+    // 3) Set up the writer exactly as before
+    FFmpegWriter writer("/home/jonathan/Downloads/performance‐cachetest.mp4");
+    writer.SetAudioOptions("aac", 48000, 192000);
+    writer.SetVideoOptions("libx264", 1280, 720, Fraction(30, 1), 5000000);
+    writer.Open();
+
+    // 4) Forward pass: for each frame 1…N, tell the cache thread to seek to that frame,
+    //    then immediately call cache->GetFrame(frame), which will block only if that frame
+    //    hasn’t been decoded into the cache yet.
     auto t0 = std::chrono::high_resolution_clock::now();
-    for (long int frame = 1; frame <= total_frames; frame++) {
-        float percent = (float(frame) / total_frames) * 100.0f;
-        std::cout << "Forward: Requesting Frame #: " << frame
-                  << " (" << percent << "%)\n";
-        std::shared_ptr<Frame> f = r.GetFrame(frame);
-        w.WriteFrame(f);
+    cache->setSpeed(1);
+    for (int64_t f = 1; f <= total_frames; ++f) {
+        float pct = (float(f) / total_frames) * 100.0f;
+        std::cout << "Forward: requesting frame " << f << " (" << pct << "%)\n";
+
+        cache->Seek(f);                   // signal “I need frame f now (and please prefetch f+1, f+2, …)”
+        std::shared_ptr<Frame> framePtr = timeline.GetFrame(f);
+        writer.WriteFrame(framePtr);
     }
     auto t1 = std::chrono::high_resolution_clock::now();
     auto forward_ms = std::chrono::duration_cast<std::chrono::milliseconds>(t1 - t0).count();
 
-    // --- Measure backward pass ---
+    // 5) Backward pass: same idea in reverse
     auto t2 = std::chrono::high_resolution_clock::now();
-    for (long int frame = total_frames; frame >= 1; frame--) {
-        float percent = (float(total_frames - frame + 1) / total_frames) * 100.0f;
-        std::cout << "Backward: Requesting Frame #: " << frame
-                  << " (" << percent << "%)\n";
-        std::shared_ptr<Frame> f = r.GetFrame(frame);
-        w.WriteFrame(f);
+    cache->setSpeed(-1);
+    for (int64_t f = total_frames; f >= 1; --f) {
+        float pct = (float(total_frames - f + 1) / total_frames) * 100.0f;
+        std::cout << "Backward: requesting frame " << f << " (" << pct << "%)\n";
+
+        cache->Seek(f);
+        std::shared_ptr<Frame> framePtr = timeline.GetFrame(f);
+        writer.WriteFrame(framePtr);
     }
     auto t3 = std::chrono::high_resolution_clock::now();
     auto backward_ms = std::chrono::duration_cast<std::chrono::milliseconds>(t3 - t2).count();
 
-    std::cout << "\nForward pass elapsed: " << forward_ms << " ms\n";
+    std::cout << "\nForward pass elapsed:  "  << forward_ms  << " ms\n";
     std::cout << "Backward pass elapsed: " << backward_ms << " ms\n";
 
-    r.Close();
-    w.Close();
+    // 6) Shut down the cache thread, close everything
+    cache->StopThread(10000);  // politely tells run() to exit, waits up to 10s
+    reader.Close();
+    writer.Close();
+    timeline.Close();
     return 0;
 }