video-v1/vav2/docs/working/Phase1_Implementation_Summary.md

Phase 1 Implementation Summary - Playback Timing Fix

Date: 2025-10-07 Status: ✅ Implemented, Ready for Testing

Changes Made

1. PlaybackController.h

Added:

• Forward declaration: class FrameProcessor;
• Public method: void SetFrameProcessor(FrameProcessor* processor)
• Public method: bool IsFrameProcessing() const
• Private member: FrameProcessor* m_frameProcessor = nullptr

Lines changed: +5 lines

2. PlaybackController.cpp

Added:

• Include: #include "FrameProcessor.h"
• Implementation of IsFrameProcessing() method
• Frame completion wait logic in TimingThreadLoop()

Modified:

void PlaybackController::TimingThreadLoop()
{
    // ... existing code ...

    while (!m_shouldStopTiming && m_isPlaying) {
        auto frameStart = std::chrono::high_resolution_clock::now();

        // Signal frame processing
        if (m_frameReadyCallback) {
            m_frameReadyCallback();
        }

        // ✅ NEW: Wait for frame processing completion (max 100ms timeout)
        int waitCount = 0;
        while (IsFrameProcessing() && waitCount < 100) {
            std::this_thread::sleep_for(std::chrono::milliseconds(1));
            waitCount++;
        }

        if (waitCount >= 100) {
            LOGF_WARNING("[PlaybackController] Frame processing timeout after 100ms");
        }

        // Update frame counter
        m_currentFrame++;
        m_currentTime = m_currentFrame / m_frameRate;

        // Sleep until next frame
        std::this_thread::sleep_until(nextFrame);
    }
}

bool PlaybackController::IsFrameProcessing() const
{
    return m_frameProcessor && m_frameProcessor->IsProcessing();
}

Lines changed: +20 lines

3. VideoPlayerControl2.xaml.cpp

Modified:

void VideoPlayerControl2::LoadVideo(...)
{
    // ... existing code ...

    if (success) {
        // ✅ NEW: Link FrameProcessor to PlaybackController
        if (m_frameProcessor) {
            m_playbackController->SetFrameProcessor(m_frameProcessor.get());
            m_frameProcessor->PrepareVideoTexture(videoWidth, videoHeight);
        }

        // ... rest of code ...
    }
}

Lines changed: +1 line

---

Total Changes

• Files modified: 3
• Lines added: ~26 lines
• Complexity: Very Low
• Risk: Minimal

---

How It Works

Before Fix (Broken)

Timeline:
0ms     : Timing thread signals "process frame N"
0ms     : FrameProcessor starts decode
10-15ms : CUDA decode completes
20-25ms : UI render completes
33.33ms : Timing thread signals "process frame N+1" (DOESN'T WAIT!)
         → If frame N not done, m_frameProcessing check FAILS
         → Frame N+1 DROPPED
         → Result: Jerky playback

After Fix (Working)

Timeline:
0ms     : Timing thread signals "process frame N"
0ms     : FrameProcessor starts decode (m_frameProcessing = true)
10-15ms : CUDA decode completes
20-25ms : UI render completes
25ms    : FrameProcessor done (m_frameProcessing = false)
25ms    : Timing thread detects completion via IsFrameProcessing()
25ms    : Timing thread advances frame counter
33.33ms : Sleep completes, signal "process frame N+1"
         → NO FRAME DROPS
         → Result: Smooth playback

---

Build Status

✅ Build successful

• VavCore-debug.dll: Built
• Vav2Player.exe: Built
• No errors, no warnings (related to changes)

---

Testing Instructions

1. Launch Application

cd "D:/Project/video-av1/vav2/platforms/windows/applications/vav2player/Vav2Player/x64/Debug/Vav2Player"
./Vav2Player.exe

2. Load Test Video

• Use file picker to load: D:/Project/video-av1/sample/simple_test.webm
• Or any 30fps AV1/VP9 video

3. Observe Playback

Expected Results:

• ✅ Smooth playback (no jerking)
• ✅ Consistent 30fps
• ✅ Zero frame drops

Check Logs:

[PlaybackController] Frame processing timeout after 100ms  ← Should NOT appear
[FrameProcessor] Frame dropped (#X)                         ← Should be 0

4. Long Duration Test

• Play for 5 minutes
• Monitor for any jerking
• Check frame drop counter: should remain 0

---

Success Criteria

Primary

• Video plays smoothly (no "통통 튐")
• No frame drops during 5-minute playback
• User confirms smooth visual playback

Secondary

• Logs show no timeout warnings
• Frame intervals consistent at 33.33ms
• CPU usage same as before

---

If Problems Occur

Rollback Procedure

1. Revert PlaybackController.h:

   • Remove forward declaration
   • Remove SetFrameProcessor and IsFrameProcessing methods
   • Remove m_frameProcessor member

2. Revert PlaybackController.cpp:

   • Remove FrameProcessor.h include
   • Restore original TimingThreadLoop
   • Remove IsFrameProcessing implementation

3. Revert VideoPlayerControl2.xaml.cpp:

   • Remove SetFrameProcessor call

Time: < 5 minutes

Alternative: Git Revert

git diff HEAD  # Review changes
git checkout -- <file>  # Revert specific file

---

Next Steps (Phase 2)

If Phase 1 successful:

• Proceed with Fence removal (optional cleanup)
• See: Playback_Timing_Fix_Design.md Phase 2

If Phase 1 issues:

• Debug specific problem
• Check FrameProcessor::IsProcessing() behavior
• Verify m_frameProcessing atomic flag operations

---

Technical Notes

Thread Safety

• IsFrameProcessing() reads atomic bool m_frameProcessing ✅ Thread-safe
• SetFrameProcessor() called during initialization only ✅ No race condition
• Non-owning pointer (FrameProcessor lifetime > PlaybackController) ✅ Safe

Performance Impact

• Wait loop: 1ms sleep per iteration
• Typical wait: 20-25ms (20-25 iterations)
• CPU overhead: Negligible (< 1%)

Timeout Behavior

• Max wait: 100ms (100 iterations)
• If timeout occurs: Warning logged, playback continues
• Prevents infinite loop if frame processor hangs

---

Logs to Monitor

Good Playback

[PlaybackController] Timing thread started
[FrameProcessor] ProcessFrame START (decoded: 0, dropped: 0)
[FrameProcessor] Decode SUCCESS - frame decoded
[FrameProcessor] Render succeeded
[FrameProcessor] CLEARING m_frameProcessing flag
[PlaybackController] [No timeout warnings]

Bad Playback (Should NOT see)

[PlaybackController] Frame processing timeout after 100ms
[FrameProcessor] Frame dropped (#1) - previous frame still processing

---

Contact

Implementation: Claude Code Review: User Date: 2025-10-07