fix(engine): add anti-banding x264/x265 params for dark gradients#222
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jrusso1020 merged 1 commit intomainfrom Apr 7, 2026
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fix(engine): add anti-banding x264/x265 params for dark gradients#222jrusso1020 merged 1 commit intomainfrom
jrusso1020 merged 1 commit intomainfrom
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Add aq-mode=3 (auto-variance adaptive quantization) to CPU H.264/H.265 encoding. This redistributes bits from bright/textured areas to dark flat areas where color banding is most visible in 8-bit yuv420p output. - standard/high presets: aq-mode=3 + aq-strength=0.8 + deblock=1,1 - draft (ultrafast): aq-mode=3 only (deblock too slow for ultrafast) - GPU and VP9 encoders unaffected (have their own AQ implementations) Adds 6 regression tests verifying the params are emitted correctly. Fixes color banding on dark gradients (eval issue #3, prompts 3,5,10,14). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
miguel-heygen
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## Description Adds proper BT.709 color space metadata and full→limited range conversion to H.264/H.265 encoding. Chrome captures frames in full-range sRGB (BT.709 primaries), but without explicit color tagging, players guess the wrong color space and range — causing color shifts across iOS/Android/desktop and crushed dark values that compound the gradient banding issue fixed in #222. **What changed:** | Setting | Before | After | |---------|--------|-------| | `color_space` | `bt470bg` (guessed) | `bt709` (explicit) | | `color_primaries` | `unknown` | `bt709` | | `color_transfer` | `unknown` | `bt709` | | `color_range` | `pc` (full, wrong for H.264) | `tv` (limited, correct) | | `time_base` | `1/15360` (varies by platform) | `1/90000` (fixed) | **Approach:** - BT.709 VUI params embedded via x264-params/x265-params (`colorprim=bt709:transfer=bt709:colormatrix=bt709`) — ensures the bitstream itself carries color info - FFmpeg-level metadata flags (`-colorspace:v bt709`, etc.) — belt-and-suspenders - `scale=in_range=pc:out_range=tv` filter converts Chrome's full-range output to TV/limited range - VAAPI path chains the range filter with existing `format=nv12,hwupload` - `-video_track_timescale 90000` for consistent cross-platform A/V timing (same as Remotion) - VP9 and ProRes encoding unaffected ## Testing - Verified via ffprobe: all 5 color metadata fields now correct - Directly tested FFmpeg args produce expected output - 40 engine tests pass (8 new: color metadata h264/h265, range filter CPU, VAAPI filter chain, GPU skip, VP9 skip, timescale) - Builds cleanly, lint + format pass
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Description
Fixes color banding on dark gradients — eval issue #3, affecting prompts 3, 5, 10, 14.
Root cause: libx264's default
aq-mode=1doesn't allocate enough bits to dark flat gradient areas. With 8-bityuv420p, subtle gradient steps get quantized to the same value, producing visible horizontal bands.Fix: Add
aq-mode=3(auto-variance adaptive quantization) via-x264-params/-x265-paramsto both chunk and streaming encoders. This redistributes bits from bright/textured areas to dark flat areas where banding is most visible.aq-mode=3onlyaq-mode=3:aq-strength=0.8:deblock=1,1aq-mode=3:aq-strength=0.8:deblock=1,1aq-mode=3— auto-variance AQ, designed for flat dark areasaq-strength=0.8— slightly below default to avoid over-softening texturesdeblock=1,1— stronger deblocking smooths quantization band boundariesTesting
#1a1a2e → #0a0a0a) — smooth gradients, no visible bandingNote: pre-commit typecheck failure is pre-existing on main (
linkedomtypes missing incorepackage).