Module multipass_quality 

Multipass encoding quality comparison.

This module provides tools to verify that multipass encoding (two-pass, lookahead-based) produces measurably better quality than single-pass encoding at the same average bitrate. The comparison uses:

• Per-frame quality scores (QP-derived or PSNR-measured)
• Bitrate distribution analysis (variance, min/max ratio)
• Quality consistency metrics (standard deviation of per-frame quality)

Verification Strategy

For a fair comparison between single-pass and multipass:

1. Encode the same source with both methods at the same target bitrate
2. Record per-frame (size, QP) tuples
3. Compare:
   • Average quality should be equal or better for multipass
   • Quality variance should be lower for multipass
   • Bitrate distribution should be smoother for multipass

Usage

use oximedia_codec::multipass_quality::{
    PassRecorder, MultipassComparison, FrameMetric,
};

let mut single = PassRecorder::new("single-pass");
let mut multi  = PassRecorder::new("two-pass");

// Record frames from each encoding session
single.record(FrameMetric { size_bytes: 5000, qp: 28, is_keyframe: false });
multi.record(FrameMetric { size_bytes: 4800, qp: 27, is_keyframe: false });
// ... more frames ...

let cmp = MultipassComparison::compare(&single, &multi);
// multipass should have equal or better average QP

Structs

FrameMetric

Per-frame metric recorded during encoding.

MultipassComparison

Result of comparing two encoding passes.

PassRecorder

Records per-frame metrics for one encoding pass.