apps/web/src/pages/ai-avatar/components/ModalBRollEditor.tsx

@@ -65,10 +65,10 @@ const ModalBRollEditor: React.FC<ModalBRollEditorProps> = ({
   const [pipPosition, setPipPosition] = useState<PipPosition>("top-right")
   const [pipScale, setPipScale] = useState(0.3)
 
-  /** 文案分句（使用后端精确时间戳） */
+  /** 文案分句（优先使用后端精确时间戳，降级为字数比例估算） */
   const sentences = useMemo(
-    () => splitScriptIntoSentences(scriptText, sentenceTimings),
-    [scriptText, sentenceTimings],
+    () => splitScriptIntoSentences(scriptText, sentenceTimings, _outputDuration),
+    [scriptText, sentenceTimings, _outputDuration],
   )
 
   /** 已被现有 segments 占用的素材 id 集合（标灰、禁止重复选择） */
@@ -145,7 +145,7 @@ const ModalBRollEditor: React.FC<ModalBRollEditorProps> = ({
     setSelectedAsset(asset)
   }
 
-  /** 确认添加一段 B-roll（⑥ 时间取所选句子的估算起止） */
+  /** 确认添加一段 B-roll（⑥ 时间取所选句子的精确起止，后端静音检测 / 前端字数比例降级） */
   const handleConfirm = () => {
     if (!selectedAsset || !selectedSentence) return
     const startTime = selectedSentence.startTime
@@ -267,11 +267,9 @@ const ModalBRollEditor: React.FC<ModalBRollEditorProps> = ({
                           >
                             <span className="aa-sentence-item__idx">{sent.index + 1}</span>
                             <span className="aa-sentence-item__text">{sent.text}</span>
-                            {sent.endTime > 0 && (
-                              <span className="aa-sentence-item__time">
-                                {sent.startTime.toFixed(1)}-{sent.endTime.toFixed(1)}s
-                              </span>
-                            )}
+                            <span className="aa-sentence-item__time">
+                              {sent.startTime.toFixed(1)}-{sent.endTime.toFixed(1)}s
+                            </span>
                           </button>
                         )
                       })}

apps/web/src/pages/ai-avatar/components/PanelCoverAndGenerate.tsx

@@ -120,7 +120,7 @@ const PanelCoverAndGenerate: React.FC<PanelCoverAndGenerateProps> = ({
       wordBreak: "break-word",
       whiteSpace: "pre-wrap",
       color: titleConfig.color || "#ffffff",
-      fontSize: `${(titleConfig.size || 28) * 0.55}px`, // 预览容器缩放，与 PanelLipsyncPreview 对齐
+      fontSize: `${(titleConfig.size || 48) * 0.35}px`, // 预览容器缩放，与 PanelLipsyncPreview 对齐
       fontFamily: getFontFamily(titleConfig.font),
       fontWeight: titleConfig.bold ? "bold" : "normal",
       fontStyle: titleConfig.italic ? "italic" : "normal",

apps/web/src/pages/ai-avatar/components/PanelLipsyncPreview.tsx

@@ -58,7 +58,7 @@ export function PanelLipsyncPreview({
         position: "absolute",
         color: titleConfig.color || "#ffffff",
         fontFamily: titleConfig.font || "思源黑体",
-        fontSize: `${(titleConfig.size || 28) * 0.55}px`,
+        fontSize: `${(titleConfig.size || 48) * 0.35}px`,
         fontWeight: titleConfig.bold ? 700 : 400,
         fontStyle: titleConfig.italic ? "italic" : "normal",
         textAlign: "center",

apps/web/src/pages/ai-avatar/types.ts

@@ -122,7 +122,7 @@ export const DEFAULT_TITLE_CONFIG: AiAvatarTitleConfig = {
   title: "",
   position: "bottom",
   font: "思源黑体",
-  size: 28,
+  size: 48,
   bold: true,
   italic: false,
   stroke: false,

apps/web/src/pages/ai-avatar/utils/contract.ts

@@ -39,7 +39,7 @@ export function buildTitleConfigPayload(cfg: AiAvatarTitleConfig): Record<string
     text,
     enabled: true,
     font: cfg.font || "思源黑体",
-    font_size: Math.round(cfg.size) || 28,
+    font_size: Math.round(cfg.size) || 48,
     font_color: cfg.color || "#ffffff",
     position,
     bold: !!cfg.bold,

apps/web/src/pages/ai-avatar/utils/sentences.ts

@@ -28,6 +28,7 @@ export interface ScriptSentence {
 export function splitScriptIntoSentences(
   scriptText: string,
   sentenceTimings?: SentenceTiming[] | null,
+  outputDuration: number = 0,
 ): ScriptSentence[] {
   const text = (scriptText || "").trim()
   if (!text) return []
@@ -39,21 +40,45 @@ export function splitScriptIntoSentences(
 
   const sentences: ScriptSentence[] = []
   let accChar = 0
+  const totalChars = rawParts.reduce((sum, p) => sum + p.replace(/\s/g, "").length, 0)
+  // 如果后端返回了完整的时间戳（至少有一个有效结束时间），使用精确时间
+  const hasBackendTimings =
+    sentenceTimings &&
+    sentenceTimings.length > 0 &&
+    sentenceTimings.some((t) => (t.end_time ?? 0) > 0)
+
+  // 若有后端时间戳，取音频总时长；否则用外部传入的 outputDuration 做字数比例降级
+  const audioDuration = hasBackendTimings
+    ? (sentenceTimings![sentenceTimings!.length - 1]?.end_time ?? 0)
+    : outputDuration
+
   rawParts.forEach((part, i) => {
     const charCount = part.replace(/\s/g, "").length
-    // 从后端精确时间戳获取；无数据时返回 0
-    const timing = sentenceTimings?.[i]
-    const startTime = timing?.start_time ?? 0
-    const endTime = timing?.end_time ?? 0
-
-    sentences.push({
-      index: i,
-      text: part,
-      charCount,
-      startChar: accChar,
-      startTime,
-      endTime,
-    })
+    if (hasBackendTimings) {
+      // 使用后端精确时间戳
+      const timing = sentenceTimings![i]
+      sentences.push({
+        index: i,
+        text: part,
+        charCount,
+        startChar: accChar,
+        startTime: timing?.start_time ?? 0,
+        endTime: timing?.end_time ?? 0,
+      })
+    } else {
+      // 降级方案：按字数比例估算（必须保证有时间，否则B-roll无法定位）
+      const startTime = totalChars > 0 ? (accChar / totalChars) * (audioDuration || 0) : 0
+      const endTime =
+        totalChars > 0 ? ((accChar + charCount) / totalChars) * (audioDuration || 0) : 0
+      sentences.push({
+        index: i,
+        text: part,
+        charCount,
+        startChar: accChar,
+        startTime: Math.round(startTime * 100) / 100,
+        endTime: Math.round(endTime * 100) / 100,
+      })
+    }
     accChar += charCount
   })
 

packages/domain/video_filter_builder.py

@@ -481,7 +481,7 @@ def build_title_drawtext_filter(
 
     # ── 样式参数 ──
     font_name = title_config.get("font") or title_config.get("font_preset") or "思源黑体"
-    font_size = int(title_config.get("font_size") or title_config.get("size") or 28)
+    font_size = int(title_config.get("font_size") or title_config.get("size") or 48)
     font_color = title_config.get("font_color") or title_config.get("color") or "#ffffff"
     # 去掉 # 前缀（drawtext 用纯 hex 或颜色名）
     if font_color.startswith("#"):