FlashbackTurbo

A Fabric addon for Flashback that drastically speeds up video export.

What it does

FlashbackTurbo replaces Flashback's PNG-sequence encoder with a parallel pipeline (N-1 threads), configurable zlib compression level, and color-type-2 output when transparency is off. Adds FFmpeg threading tunes per encoder and removes the silent 4K resolution cap.

Performance

Measured on a real 1.21.11 replay, 10-second slice at 1920x1080 (603 frames):

Speedup: 10.95x

Gains vary by CPU core count and disk speed:

• 16-core + NVMe: ~12-15x
• 4-core + SSD: ~4-6x
• Older 2-core + HDD: ~2-3x

Quality

Zero visual loss. PNG output uses zlib level 1 (vs Mojang's hardcoded level 6) - pixel-decoded output is strictly identical, only the compressed file size differs slightly.

Hooks

• H2 parallel PNG writer (N-1 threads)
• H3 configurable zlib level (default L1)
• H4 removed silent 4K downscale cap
• H6 FFmpeg threading tunes per encoder
• H7 color type 2 (RGB) when transparency off

All hooks are toggleable via config/flashbackturbo.json.

Requirements

• Minecraft 1.21.9 / 1.21.10 / 1.21.11
• Fabric Loader >= 0.19.2
• Flashback >= 0.39.5
• Fabric API
• Java 21

Sibling project

From the same author: MultiView for multi-POV Flashback replays.