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vmaf-tune Phase E — Bitrate Ladder

vmaf-tune ladder builds a per-title ABR ladder from sampled (resolution, target-VMAF) cells. It scores the sampled points, constructs the Pareto frontier, picks a bounded number of rungs, and emits an HLS, DASH, or JSON manifest.

The implementation lives in tools/vmaf-tune/src/vmaftune/ladder.py and the CLI entry point is wired in tools/vmaf-tune/src/vmaftune/cli.py.

Quick Start

vmaf-tune ladder \
    --src ref.yuv \
    --encoder libx264 \
    --resolutions 1920x1080,1280x720,854x480 \
    --target-vmafs 95,92,88 \
    --quality-tiers 5 \
    --format hls \
    --output master.m3u8

Pipeline

  1. build_ladder() samples every (resolution, target_vmaf) pair.
  2. The default sampler runs the canonical 5-point CRF sweep and picks the row closest to the target.
  3. convex_hull() removes dominated bitrate/quality points.
  4. select_knees() chooses the requested number of rungs along the hull.
  5. emit_manifest() writes HLS, DASH, or JSON.

Programmatic callers can pass sampler= to build_ladder() for a custom grid, a precomputed corpus, or a true bisect-backed sampler.

CLI Flags

Flag Default Notes
--src PATH — Source clip.
--encoder NAME libx264 Any registered codec adapter.
--resolutions LIST — Comma-separated WxH list.
--target-vmafs LIST — Comma-separated VMAF targets.
--quality-tiers N 5 Number of final rungs.
--format hls hls, dash, or json.
--spacing log_bitrate Knee spacing strategy: log_bitrate or uniform.
--with-uncertainty off Apply conformal-interval rung pruning/insertion when interval data is present.
--output PATH stdout Manifest destination.

See Also