Function assess_alignment_quality

ffsubsync/ffsubsync.py:145–174

Return reasons an alignment looks too low-quality to trust (empty = trust it). Used by --skip-sync-on-low-quality to decide whether to leave the subtitles unmodified rather than apply a probably-wrong shift. A negative score means the best alignment is anti-correlated; an implausibly la

(
    best_score: float,
    offset_seconds: float,
    scale_factor: float,
    *,
    min_score: float,
    max_offset_seconds: float,
    max_framerate_deviation: float,
)

def assess_alignment_quality(
    best_score: float,
    offset_seconds: float,
    scale_factor: float,
    *,
    min_score: float,
    max_offset_seconds: float,
    max_framerate_deviation: float,
) -> List[str]:
    """Return reasons an alignment looks too low-quality to trust (empty = trust it).

    Used by --skip-sync-on-low-quality to decide whether to leave the subtitles
    unmodified rather than apply a probably-wrong shift. A negative score means the
    best alignment is anti-correlated; an implausibly large offset or framerate
    scale suggests a spurious match.
    """
    reasons: List[str] = []
    if best_score < min_score:
        reasons.append("score %.1f < %.1f" % (best_score, min_score))
    if abs(offset_seconds) > max_offset_seconds:
        reasons.append(
            "|offset| %.1fs > %.1fs" % (abs(offset_seconds), max_offset_seconds)
        )
    framerate_deviation = abs(scale_factor - 1.0)
    if framerate_deviation > max_framerate_deviation:
        reasons.append(
            "framerate deviation %.3f > %.3f"
            % (framerate_deviation, max_framerate_deviation)
        )
    return reasons


def try_sync(