# 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**:
```cpp
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**:
```cpp
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
```bash
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
```bash
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