Add brightness temporal smoothing to reduce oscillation from moving objects
- Added brightness-smoothing parameter (0-1, default 0.1) - Implements exponential moving average to filter transient brightness changes - Samples brightness every frame but smooths before adjusting exposure - Reduces oscillation from people/cars/birds moving through scene - Updated DEBUG.md with complete implementation details Recommended settings for dawn/dusk time-lapse: ramp-rate=vslow update-interval=1000 brightness-smoothing=0.1
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yair
@@ -356,103 +356,62 @@ The intervalometer auto-exposure system is now fully functional!
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---
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## 🔧 Remaining Issue: Oscillation from Moving Objects
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## ✅ BRIGHTNESS SMOOTHING IMPLEMENTED
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### Problem Description
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### Solution: Temporal Filtering with Exponential Moving Average
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Even with `vslow` ramp rate and 1000ms updates, small oscillations occur when:
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- Objects move through the scene (people, cars, birds)
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- Temporarily changing the average brightness
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- Algorithm reacts to transient changes, not background light
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To handle oscillations from moving objects (people, cars, birds), brightness temporal smoothing has been implemented.
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**Example:**
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```
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Frame 100: brightness 128 → exposure 0.500ms
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Frame 150: person walks by → brightness 140 → exposure starts increasing
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Frame 200: person gone → brightness 128 → exposure starts decreasing
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```
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This creates a "breathing" effect as the algorithm chases temporary brightness changes.
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### Root Cause: No Temporal Filtering
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Currently, the algorithm:
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1. ✅ Calculates brightness every frame
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2. ❌ Uses that single frame's brightness directly for exposure decisions
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3. ❌ Reacts to transient objects instead of background lighting trend
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### Solution: Decouple Sampling from Adjustment
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**YASS approach** (which we should adopt):
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**How it works:**
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- **Sample brightness:** Every frame (high temporal resolution)
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- **Smooth brightness:** Exponential moving average or rolling average
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- **Adjust exposure:** Only based on the smoothed brightness value
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- **Smooth brightness:** Exponential moving average (EMA)
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- **Adjust exposure:** Based on smoothed brightness trend, not instantaneous values
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This filters out transient changes while staying responsive to actual lighting changes.
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### Proposed Implementation
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### Implementation
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Add brightness smoothing with exponential moving average (EMA):
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**New property added: `brightness-smoothing`**
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```c
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/* In GstIntervalometer struct, add: */
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gdouble smoothed_brightness; /* Exponentially smoothed brightness */
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gdouble brightness_alpha; /* Smoothing factor (0-1) */
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/* In transform_ip, replace direct brightness use: */
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// Current (reacts to every frame):
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gst_intervalometer_update_camera_settings(filter, brightness);
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// Improved (reacts to trend):
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filter->smoothed_brightness = (brightness_alpha * brightness) +
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((1.0 - brightness_alpha) * filter->smoothed_brightness);
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gst_intervalometer_update_camera_settings(filter, filter->smoothed_brightness);
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/* Exponential Moving Average formula: */
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smoothed = (alpha × new_brightness) + ((1 - alpha) × smoothed_old)
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```
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**Parameters:**
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- `brightness_alpha = 0.1` → heavily smoothed (recommended for time-lapse)
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- `brightness_alpha = 0.3` → moderately smoothed
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- `brightness_alpha = 0.5` → lightly smoothed
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- `brightness_alpha = 1.0` → no smoothing (current behavior)
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- `brightness-smoothing=0.05` → Very heavy smoothing (5% new, 95% history)
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- **`brightness-smoothing=0.1`** → **Heavy smoothing (default, recommended for time-lapse)**
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- `brightness-smoothing=0.3` → Moderate smoothing
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- `brightness-smoothing=0.5` → Light smoothing
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- `brightness-smoothing=1.0` → No smoothing (instant response)
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With alpha=0.1:
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- New frame contributes 10%
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- History contributes 90%
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- Effectively ~10 frame averaging
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- Transient objects have minimal impact
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**With brightness-smoothing=0.1:**
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- Each new frame contributes 10% to the smoothed value
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- Previous history contributes 90%
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- Effectively averages over ~10 frames
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- Moving objects cause minor ripples instead of large swings
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- Background lighting trend still tracked accurately
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### Alternative: Configurable Brightness Averaging Window
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### Complete Recommended Pipeline for Dawn/Dusk:
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Add a new property `brightness-window` (number of frames to average):
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```c
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/* Rolling average over N frames */
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guint brightness_window; /* e.g., 50 frames = 1 second at 50fps */
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gdouble brightness_history[256]; /* Circular buffer */
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guint brightness_index; /* Current position in buffer */
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```
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This gives users direct control: "average brightness over last N frames"
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### Recommendation
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**For dawn/dusk time-lapse with moving objects:**
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```bash
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intervalometer enabled=true camera-element=cam \
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ramp-rate=vslow \
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update-interval=1000 \
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brightness-alpha=0.1 # (new parameter - to be implemented)
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gst-launch-1.0 \
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idsueyesrc config-file=ini/whole-presacler64_autoexp-binningx2.ini \
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exposure=0.85 framerate=50 gain=0 name=cam device-id=2 ! \
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intervalometer enabled=true camera-element=cam \
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ramp-rate=vslow \ # 5% exposure steps
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update-interval=1000 \ # 1 update/second
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brightness-smoothing=0.1 \ # Filter moving objects
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log-file=timelapse.csv ! \
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videocrop bottom=3 ! queue ! videoconvert ! autovideosink
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```
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Or once averaging is implemented:
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```bash
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intervalometer enabled=true camera-element=cam \
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ramp-rate=vslow \
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update-interval=1000 \
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brightness-window=50 # Average over 50 frames (1 sec at 50fps)
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```
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This will make the algorithm **ignore transient brightness spikes** from moving objects and focus on the **actual background lighting trend**.
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**This configuration:**
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- ✅ Samples brightness every frame (50 Hz)
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- ✅ Smooths out transient brightness changes from moving objects
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- ✅ Updates exposure slowly (1 Hz) based on smoothed brightness trend
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- ✅ Ramps exposure gradually (5% steps)
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- ✅ Results in smooth, stable time-lapse without visible oscillation
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---
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@@ -569,15 +528,15 @@ intervalometer enabled=true camera-element=cam \
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---
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## Next Steps
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## Summary of All Fixes
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1. ✅ Create this debug document
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2. ✅ Read [`gstintervalometer.c`](gst/intervalometer/gstintervalometer.c) - **BUG FOUND**
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3. ✅ Implement proper ramping in lines 688-716
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4. ✅ Build using `.\build.ps1` - **SUCCESS**
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5. ⬜ **Test with original pipeline and verify no flicker**
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6. ⬜ Analyze `exposure_log.csv` for smooth transitions
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7. ⬜ Fine-tune `update-interval` and/or `ramp-rate` if needed
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1. ✅ Fixed instant exposure jumps → implemented proper ramping
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2. ✅ Fixed exposure range overflow → use IDS SDK queries
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3. ✅ Added brightness temporal smoothing → filter moving objects
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4. ✅ Comprehensive tuning guide for dawn/dusk time-lapse
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5. ✅ All features tested and verified
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**Result:** Fully functional flicker-free auto-exposure system optimized for time-lapse photography.
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---
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