Wan Vace Auto Joiner

WAN VACE Auto Joiner v2.0.0 (ComfyUI Custom Nodes)

Seamlessly join multiple video clips in a folder using WAN VACE and ComfyUI Easy-Use For Loop automation — with one-click solution.

This node set ensures:

• VACE runs exactly N-1 times for N input videos
• Seamless transitions with automatic color/brightness correction
• Audio preservation from original clips
• Finalization runs once, after the loop completes

Nodes appear under: WAN VACE / Auto Joiner

---

🆕 What's New in v2.0.0

Seamless Transitions

VACE can introduce brightness/color shifts at transition boundaries. v2.0.0 automatically corrects this with:

• Temporal Color Smoothing — Gaussian + linear interpolation across transition regions
• Per-Channel Correction — Independent R, G, B adjustment for accurate color matching
• Dynamic Calculation — All correction values computed from your actual source frames (no hardcoded values)

Audio Support

• Automatic Audio Transfer — Extracts and concatenates audio from all source clips
• Direct Video Combine Integration — Standard ComfyUI AUDIO output connects directly to VHS Video Combine
• Fail-Safe Handling — Generates silent audio track when source clips have no audio (prevents workflow errors)

---

Key Features

| Feature | Description | |---------|-------------| | ✅ One-click batch joining | Process unlimited video clips automatically | | ✅ Seamless transitions | No visible brightness/color jumps between clips | | ✅ Audio preservation | Original audio transferred to final output | | ✅ Loop barrier system | Prevents early exit & race conditions | | ✅ Clean lifecycle | INIT → PROCESS → FINALIZE | | ✅ Security | Input sanitization prevents path traversal |

---

Requirements

| Requirement | Notes | |-------------|-------| | ComfyUI | Base requirement | | ComfyUI-Easy-Use | Required for For Loop nodes | | WAN VACE workflow | Your existing VACE setup | | ffmpeg | Required for audio features (optional) | | scipy | Recommended for best smoothing (optional, has numpy fallback) |

---

Installation

Option 1 — ComfyUI-Manager (Recommended)

1. Open ComfyUI → Manager
2. Go to Install Custom Nodes
3. Search for Wan Vace Auto Joiner
4. Install and restart ComfyUI

Option 2 — Manual Install

cd ComfyUI/custom_nodes
git clone https://github.com/Rhovanx/wan_vace_auto_joiner.git

Restart ComfyUI.

Optional Dependencies

# For best color smoothing results
pip install scipy

# For audio features (check if already installed)
ffmpeg -version

---

The Three Nodes

| Node | Display Name | Location | Purpose | |------|--------------|----------|---------| | WanVaceAutoJoiner | WAN VACE Auto Joiner | Inside loop | INIT (first iteration) / PROCESS (subsequent) | | WanVaceAutoJoinerSave | WAN VACE Auto Joiner – Save | Inside loop | Saves VACE output, acts as loop barrier | | WanVaceAutoJoinerFinalize | WAN VACE Auto Joiner – Finalize | After loop | Applies smoothing, outputs frames + audio |

---

Finalize Node Options (v2.0.0)

| Option | Default | Description | |--------|---------|-------------| | smooth_transitions | ✅ True | Enable temporal color smoothing | | smooth_window | 12 | Gaussian sigma (1-30, higher = smoother) | | blend_region | 25 | Context frames before/after VACE (10-50) | | transfer_audio | ✅ True | Extract audio from source clips | | cleanup | ❌ False | Delete temp folder after completion |

---

Output Connections

WAN VACE Auto Joiner - Finalize
├── batch_images ────→ Video Combine (images)
├── audio ───────────→ Video Combine (audio)
├── frame_rate ──────→ Video Combine (frame_rate)
├── status ──────────→ (optional debug output)
└── is_complete ─────→ (optional boolean flag)

---

Workflow Setup

1️⃣ Prepare Input Directory

Clips must follow this naming format:

clip_00001.mp4
clip_00002.mp4
clip_00003.mp4
...

The prefix (clip) is configurable in the Auto Joiner node.

2️⃣ Set Loop Count

For N videos, set:

For Loop Start → total = N - 1

| Videos | Loop Total | |--------|------------| | 3 | 2 | | 4 | 3 | | 5 | 4 | | 10 | 9 |

3️⃣ Connect the Nodes

For Loop Start ─────────────► For Loop End (flow)
        │
        ├── value1 ─► Save ─► initial_value1
        │
        └── index ─► Auto Joiner
                           │
                           ▼
                      WAN VACE
                           │
                       VAE Decode
                           │
                           └──► Save

After loop:
For Loop End (value1) ─────► Finalize ─────► Video Combine
                                  │              │
                                  └── audio ─────┘

4️⃣ Run Once

Queue the workflow one time — the loop handles everything automatically.

---

How Transition Smoothing Works

The Problem

VACE processes 33 frames per transition (16 from clip A + 17 from clip B). The diffusion process can shift brightness and color temperature, creating visible "pulses" at transition points.

The Solution

v2.0.0 applies temporal color smoothing:

1. Analyzes brightness and R/G/B values across the transition region
2. Creates smooth target curves using Gaussian smoothing + linear interpolation
3. Calculates per-frame correction factors dynamically from your source material
4. Applies corrections to eliminate visible jumps

Before: Transitions show +3-6 point brightness jumps
After: Transitions show <1 point variation (imperceptible)

---

Audio Handling

| Scenario | Behavior | |----------|----------| | All clips have audio | Audio extracted and concatenated | | Some clips have audio | Available audio extracted | | No clips have audio | Silent track generated | | ffmpeg not installed | Silent track generated | | transfer_audio = False | Silent track generated |

The audio output is always valid — you can permanently connect it to Video Combine without workflow errors.

---

Troubleshooting

Transitions still visible

• Increase smooth_window (try 15-20)
• Increase blend_region (try 30-40)
• Ensure smooth_transitions is enabled

No audio in output

• Check if source clips have audio tracks
• Verify ffmpeg is installed: ffmpeg -version
• Check console for [WAN VACE Auto Joiner] messages

Loop exits early

• Ensure value1 passes through the Save node
• Do not use FLOW_CONTROL for the barrier

Finalize runs too early

• Confirm Finalize is connected after For Loop End
• Do not place Finalize inside the loop

---

FAQ

Why temporal smoothing?
VACE's diffusion process modifies all 33 frames, not just the masked region. This creates color/brightness inconsistencies that are visible to the human eye. Smoothing corrects these artifacts automatically.

Are the correction values hardcoded?
No. All correction factors are calculated dynamically from your actual source frames at runtime. The algorithm adapts to any video content.

Why not FLOW_CONTROL?
FLOW_CONTROL does not block asynchronous WAN VACE execution. The value1 barrier enforces true dependency completion.

Can I disable smoothing?
Yes, set smooth_transitions to False in the Finalize node. You'll get the raw VACE output.

What if scipy isn't installed?
The code falls back to a numpy-based Gaussian filter. Results are similar but scipy is slightly more accurate.

---

Changelog

v2.0.0 (Major Release)

• ✨ NEW: Temporal color smoothing for seamless transitions
• ✨ NEW: Per-channel (R, G, B) correction
• ✨ NEW: Audio transfer from original clips
• ✨ NEW: Standard ComfyUI AUDIO output
• ✨ NEW: Fail-safe silent audio generation
• 🔒 Input sanitization for security
• 📦 Dynamic correction (no hardcoded values)

v1.0.0

• Initial release
• Three-node system (Auto Joiner, Save, Finalize)
• Loop barrier mechanism
• Zero VACE overhead design

---

License

MIT

---

Credits

• WAN VACE — Alibaba's video-to-video consistency model
• ComfyUI-Easy-Use — For Loop implementation
• ComfyUI-VideoHelperSuite — Video Combine node compatibility