refactor(video-pipeline): 将 CapCut 组装脚本拆分为模块化架构
将 monolith 的 capcut_assemble.js 重构为核心编排器，提取基础设施层（capcut-api）、时间线算法（capcut-timeline）和轨道操作（capcut-tracks）为独立模块。此拆分使 Agent 未来对字幕风格、Ken Burns、转场、特效等调整只需关注 capcut-tracks.js，无需理解全流程编排逻辑。
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229
.claude/skills/video-from-script/scripts/lib/capcut-timeline.js
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229
.claude/skills/video-from-script/scripts/lib/capcut-timeline.js
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/**
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* 时间线构建 + 视频调整策略
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*
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* 核心算法模块。纯函数 + ffmpeg，自包含可测试。
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*
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* 规则:
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* 图片模式: TTS 音频时长 = 画面时长，无音频 = 跳过
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* 视频模式: TTS 为主轴，视频通过策略适配
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* 视频比音频长 → 加速(≤2x) / 裁剪(>2x)
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* 视频比音频短 → 放缓(≥0.5x) / 画面停顿(<0.5x)
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* 所有策略失败 → 兜底截断
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*/
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const fs = require('fs')
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const path = require('path')
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const { execFile } = require('child_process')
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const { US } = require('./capcut-api')
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// ============================================================================
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// 时间线构建
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// ============================================================================
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function buildTimeline(items) {
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let offset = 0
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return items.map(item => {
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let audioDur
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if (item.segments && item.segments.length > 0) {
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audioDur = item.segments.reduce((sum, s) => sum + (s.duration || 0), 0) * US
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} else {
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audioDur = (item.audioDuration != null) ? item.audioDuration * US : 0
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}
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const videoDur = (item.videoDuration != null) ? item.videoDuration * US : 0
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const hasVideo = !!(item.video || item.videoUrl || item.url)
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// 无 TTS 音频
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if (audioDur <= 0) {
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if (hasVideo && videoDur > 0) {
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const entry = { start: offset, end: offset + videoDur, duration: videoDur, speed: 1, strategy: 'none' }
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offset += videoDur
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return entry
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}
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const entry = { start: offset, end: offset, duration: 0, speed: 1, strategy: 'none', skip: true }
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return entry
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}
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const dur = audioDur
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if (!hasVideo || videoDur <= 0) {
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const entry = { start: offset, end: offset + dur, duration: dur, speed: 1, strategy: 'none' }
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offset += dur
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return entry
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}
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// 视频模式：策略选择
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const ratio = videoDur / audioDur
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if (ratio > 1.1) {
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if (ratio <= 2) {
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const entry = { start: offset, end: offset + dur, duration: dur, speed: ratio, strategy: 'speed_up' }
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offset += dur
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return entry
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} else {
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const entry = { start: offset, end: offset + dur, duration: dur, speed: 1, strategy: 'trim' }
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offset += dur
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return entry
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}
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} else if (ratio < 0.9) {
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if (ratio >= 0.5) {
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const entry = { start: offset, end: offset + dur, duration: dur, speed: ratio, strategy: 'slow_down' }
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offset += dur
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return entry
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} else {
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const entry = {
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start: offset, end: offset + dur, duration: dur, speed: 1,
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strategy: 'freeze', freezeExtra: dur - videoDur,
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}
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offset += dur
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return entry
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}
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} else {
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const entry = { start: offset, end: offset + dur, duration: dur, speed: 1, strategy: 'none' }
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offset += dur
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return entry
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}
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})
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}
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// ============================================================================
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// 视频调整（ffmpeg 策略）
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// ============================================================================
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/**
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* ffmpeg 视频调整：根据策略适配音频时长
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*
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* 策略（按 ratio = videoDur / audioDur 选择）:
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* speed_up (ratio > 1.1, ≤2x) → setpts 压缩时间（加速）
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* trim (ratio > 2x) → 截断到目标时长
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* slow_down (ratio < 0.9, ≥0.5x) → setpts 拉长时间（慢放）
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* freeze (ratio < 0.5x) → 视频原速 + 最后一帧冻结补时长
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* none (0.9~1.1) → 无需调整
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*
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* 所有策略失败后兜底：截断到目标时长
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*/
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async function adjustVideoSpeed(videoPath, targetDurationSec, strategy = 'none', speed = 1, freezeExtraUs = 0) {
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if (!fs.existsSync(videoPath)) return videoPath
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if (strategy === 'none') return videoPath
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function fallbackTrim(cb) {
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execFile('ffmpeg', [
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'-y', '-i', videoPath,
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'-t', String(targetDurationSec),
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'-c', 'copy',
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videoPath.replace(/(\.\w+)$/, '_adj$1')
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], { timeout: 30000 }, (err) => {
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if (err) { cb(videoPath); return }
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cb(videoPath.replace(/(\.\w+)$/, '_adj$1'))
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})
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}
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return new Promise((resolve) => {
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execFile('ffprobe', [
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'-v', 'quiet', '-show_entries', 'format=duration',
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'-of', 'csv=p=0', videoPath
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], (err, stdout) => {
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if (err) { fallbackTrim(resolve); return }
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const videoDur = parseFloat(stdout.trim())
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if (!videoDur || videoDur <= 0) { fallbackTrim(resolve); return }
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const outPath = videoPath.replace(/(\.\w+)$/, '_adj$1')
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if (strategy === 'trim') {
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execFile('ffmpeg', [
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'-y', '-i', videoPath,
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'-t', String(targetDurationSec),
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'-c', 'copy',
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outPath
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], { timeout: 30000 }, (err) => {
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if (err) { console.log(` 截断失败: ${err.message}`); resolve(videoPath); return }
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console.log(` 截断: ${videoDur.toFixed(1)}s → ${targetDurationSec.toFixed(1)}s`)
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resolve(outPath)
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})
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} else if (strategy === 'speed_up') {
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const speedVal = speed.toFixed(3)
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execFile('ffmpeg', [
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'-y', '-i', videoPath,
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'-filter_complex', `setpts=PTS/${speedVal}`,
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'-an',
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outPath
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], { timeout: 30000 }, (err) => {
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if (err) {
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console.log(` 加速失败，兜底截断: ${err.message}`)
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fallbackTrim(resolve)
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return
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}
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console.log(` 加速: ${videoDur.toFixed(1)}s → ${targetDurationSec.toFixed(1)}s (${speedVal}x)`)
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resolve(outPath)
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})
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} else if (strategy === 'slow_down') {
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const factor = (1 / speed).toFixed(3)
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execFile('ffmpeg', [
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'-y', '-i', videoPath,
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'-filter_complex', `setpts=PTS*${factor}`,
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'-an',
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outPath
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], { timeout: 30000 }, (err) => {
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if (err) {
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console.log(` 放缓失败，兜底截断: ${err.message}`)
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fallbackTrim(resolve)
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return
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}
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console.log(` 放缓: ${videoDur.toFixed(1)}s → ${targetDurationSec.toFixed(1)}s (${speed.toFixed(2)}x speed)`)
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resolve(outPath)
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})
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} else if (strategy === 'freeze') {
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const freezeSec = freezeExtraUs / US
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execFile('ffmpeg', [
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'-y', '-i', videoPath,
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'-filter_complex', `tpad=stop=-1:stop_duration=${freezeSec.toFixed(3)}`,
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'-an',
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outPath
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], { timeout: 30000 }, (err) => {
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if (err) {
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console.log(` tpad freeze 失败，尝试 concat 方案: ${err.message}`)
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const lastFrame = videoPath.replace(/(\.\w+)$/, '_lastframe.png')
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const frozenVideo = videoPath.replace(/(\.\w+)$/, '_frozen.mp4')
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execFile('ffmpeg', [
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'-y', '-sseof', '-0.1', '-i', videoPath,
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'-frames:v', '1', lastFrame
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], { timeout: 10000 }, (err2) => {
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if (err2) { console.log(` concat 方案也失败，兜底截断`); fallbackTrim(resolve); return }
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execFile('ffmpeg', [
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'-y', '-loop', '1', '-i', lastFrame,
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'-t', String(freezeSec.toFixed(3)),
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'-pix_fmt', 'yuv420p',
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'-vf', 'scale=trunc(iw/2)*2:trunc(ih/2)*2',
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frozenVideo
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], { timeout: 15000 }, (err3) => {
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if (err3) {
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try { fs.unlinkSync(lastFrame) } catch (_) {}
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console.log(` 冻结帧视频生成失败，兜底截断`)
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fallbackTrim(resolve)
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return
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}
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const concatList = path.join(path.dirname(videoPath), '_freeze_concat.txt')
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fs.writeFileSync(concatList, `file '${videoPath}'\nfile '${frozenVideo}'\n`)
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execFile('ffmpeg', [
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'-y', '-f', 'concat', '-safe', '0', '-i', concatList,
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'-c', 'copy', outPath
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], { timeout: 30000 }, (err4) => {
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try { fs.unlinkSync(lastFrame); fs.unlinkSync(frozenVideo); fs.unlinkSync(concatList) } catch (_) {}
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if (err4) { console.log(` 拼接失败，兜底截断`); fallbackTrim(resolve); return }
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console.log(` 画面停顿: ${videoDur.toFixed(1)}s + 冻结 ${freezeSec.toFixed(1)}s = ${targetDurationSec.toFixed(1)}s`)
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resolve(outPath)
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})
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})
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})
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return
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}
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console.log(` 画面停顿: ${videoDur.toFixed(1)}s + 冻结 ${freezeSec.toFixed(1)}s = ${targetDurationSec.toFixed(1)}s`)
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resolve(outPath)
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})
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} else {
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resolve(videoPath)
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}
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})
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})
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}
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module.exports = { buildTimeline, adjustVideoSpeed }
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