nizika_broadcast/video.py

from typing import Any

DEFAULT_W, DEFAULT_H = 1280, 720
FONT_NAME = 'Noto Sans CJK JP'
BASE_FONT = 42
SCROLL_DURATION = 4.
STATIC_DURATION = 3.
MARGIN_X = 20
LANE_PADDING = 6


def ass_time (
        t:  float,
) -> str:
    if t < 0:
        t = 0
    cs = int (round (t * 100))
    s, cs = divmod (cs, 100)
    m, s = divmod (s, 60)
    h, m = divmod (m, 60)
    return f"{h}:{m:02d}:{s:02d}.{cs:02d}"

def escape_ass (
        text:   str,
) -> str:
    text = text.replace ('\n', ' ').replace ('\r', ' ')
    text = text.replace ('{', r'\{').replace ('}', r'\}')
    text = text.replace ('\\', r'\\')
    return text.strip ()

def approx_text_width_px (
        text:       str,
        font_size:  float,
) -> float:
    return max (40., .62 * font_size * len (text))


def build_ass (
        comments:   list[dict[str, Any]],
        w:          int,
        h:          int,
) -> str:
    header = f"""[Script Info]
ScriptType: v4.00+
PlayResX: {w}
PlayResY: {h}
ScaledBorderAndShadow: yes

[V4+ Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
Style: Danmaku,{FONT_NAME},{BASE_FONT},&H00FFFFFF,&H00000000,&H00000000,&H64000000,0,0,0,0,100,100,0,0,1,2,1,7,{MARGIN_X},{MARGIN_X},10,1

[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
"""
    events: list[str] = []

    lane_h = int (BASE_FONT + LANE_PADDING)
    lane_count = max (6, (h - 80) // lane_h)
    lane_next_free = [0.] * lane_count

    top_rows = max (1, (h // 5) // lane_h)
    bottom_rows = top_rows
    top_next_free = [0.] * top_rows
    bottom_next_free = [0.] * bottom_rows

    def pick_lane (
            next_free:  list[float],
            start:      float,
    ) -> int:
        for i, nf in enumerate (next_free):
            if nf <= start:
                return i
        return min (range (len (next_free)), key = lambda i: next_free[i])

    for c in comments:
        text = escape_ass (c['content'])
        if not text:
            continue

        start = c['vpos_ms']
        end = c['vpos_ms'] + SCROLL_DURATION
        lane = pick_lane (lane_next_free, start)
        y = 40 + lane * lane_h

        tw = approx_text_width_px (text, 1.)
        x1 = w + MARGIN_X
        x2 = -tw - MARGIN_X

        lane_next_free[lane] = start + (SCROLL_DURATION * .65)

        override = rf"{{\fs1\c&H00FFFFFF\move({int(x1)},{int(y)},{int(x2)},{int(y)})}}"
        events.append (
                f"Dialogue: 0,{ass_time(start)},{ass_time(end)},Danmaku,,0,0,0,,{override}{text}")

    return header + '\n'.join (events) + '\n'