repaire sentences

2026-10-21 19:39:04 +08:00
parent 176d722c77
commit 532d9900ba
13 changed files with 1233 additions and 60 deletions
--- a/README.md
+++ b/README.md
@@ -16,6 +16,7 @@ pip 安装依赖后即可直接播放视频。
  缓存结果；生成过程有进度条。
 - 画面字幕：句边界就绪后，当前句会叠在视频画面底部。可勾选“中文字幕”
  （快捷键 `C`）显示或关闭中文翻译；翻译由服务端生成并缓存。
+- 导出字幕：句边界就绪后可点“导出字幕”，默认保存为 UTF-8（带 BOM）的 `.ass`（中英同一条字幕避免重叠），也可另存 `.srt`。
 - AI 讲解：播放中按 `E` 或点击“AI讲解 (E)”，由服务端 AI 讲解当前句子。
 - 服务配置：点击“服务…”可填写服务器地址，或使用账号密码登录后保存令牌。
 - 调试日志：点击“调试日志”可查看/复制请求状态、耗时和错误摘要；日志保存在
--- a/media_player.py
+++ b/media_player.py
@@ -18,6 +18,7 @@
    勾选“按句跳转”后，←/→ 也会自动播放上一句/下一句
    C            开 / 关中文字幕
    E            讲解当前句子（AI）
+    导出字幕      将当前中英文字幕保存为 SRT 文件
    M            静音 / 恢复
    Ctrl+← / →   上一首 / 下一首（macOS 也支持 Command+← / →）
    N / P        下一首 / 上一首
@@ -50,9 +51,9 @@ import tkinter as tk
 from tkinter import filedialog, messagebox, ttk

 try:
-    from PIL import Image as PILImage, ImageTk
+    from PIL import Image as PILImage, ImageDraw, ImageFont, ImageTk
 except ImportError:
-    PILImage = ImageTk = None
+    PILImage = ImageDraw = ImageFont = ImageTk = None

 try:
    import vlc
@@ -80,6 +81,9 @@ SUPPORTED_EXTS = AUDIO_EXTS | VIDEO_EXTS

 LOOP_LABELS = {"off": "循环: 关", "one": "循环: 单曲", "list": "循环: 列表"}
 SPEED_PRESETS = [0.5, 0.75, 1.0, 1.25, 1.5, 2.0]
+SUBTITLE_EN_FONT_SIZE = 32
+SUBTITLE_ZH_FONT_SIZE = 28
+SUBTITLE_BG_ALPHA = 51  # 20% opaque black
 SEEK_STEP = 10
 SEEK_STEP_BIG = 60
 DEFAULT_SERVER_URL = "https://videoservice.d1kt.cn"
@@ -235,6 +239,26 @@ def _srt_timestamp(ms):
    return f"{hours:02d}:{minutes:02d}:{seconds:02d},{millis:03d}"


+def _ass_timestamp(ms):
+    """把毫秒格式化为 ASS 时间戳 H:MM:SS.cs。"""
+    total = max(0, int(ms))
+    hours, remainder = divmod(total, 3_600_000)
+    minutes, remainder = divmod(remainder, 60_000)
+    seconds, millis = divmod(remainder, 1000)
+    return f"{hours}:{minutes:02d}:{seconds:02d}.{millis // 10:02d}"
+
+
+def _escape_ass_text(text: str) -> str:
+    return (
+        str(text)
+        .replace("\\", "\\\\")
+        .replace("{", "\\{")
+        .replace("}", "\\}")
+        .replace("\n", "\\N")
+        .replace("\r", "")
+    )
+
+
 class _BaseEngine:
    """播放内核统一接口。"""

@@ -287,6 +311,9 @@ class _BaseEngine:
        """返回当前应显示的帧（PIL 图像），没有新帧时返回 None。"""
        return None

+    def set_display_size(self, width, height):
+        return None
+
    def poll_events(self):
        events = []
        while True:
@@ -306,7 +333,14 @@ class VlcEngine(_BaseEngine):

    def __init__(self):
        super().__init__()
-        args = ["--no-video-title-show", "--quiet"]
+        args = [
+            "--no-video-title-show",
+            "--quiet",
+            "--sub-text-scale=200",
+            "--freetype-background-opacity=51",
+            "--freetype-background-color=0x000000",
+            "--freetype-opacity=255",
+        ]
        if IS_MAC:
            args.append("--vout=macosx")
        self.instance = vlc.Instance(args)
@@ -550,8 +584,11 @@ class AvEngine(_BaseEngine):
        self._video_stream = None
        self._audio_stream = None
        self._video_deque = collections.deque()
-        self._video_deque_max = 6
-        self._audio_queue = queue.Queue(maxsize=64)
+        self._video_deque_max = 12
+        self._pending_video = collections.deque()
+        self._audio_queue = queue.Queue(maxsize=128)
+        self._display_size = None
+        self._prerolling = False
        self._audio_leftover = None
        self._audio_stream_obj = None
        self._audio_ok = False
@@ -571,9 +608,31 @@ class AvEngine(_BaseEngine):
        self._clock_started = time.monotonic()
        self._clock_running = False

+    def _open_container(self, path):
+        try:
+            from av.codec.hwaccel import HWAccel, hwdevices_available
+            available = set(hwdevices_available() or [])
+            if IS_MAC:
+                order = ("videotoolbox",)
+            elif IS_WIN:
+                order = ("d3d11va", "dxva2", "cuda")
+            else:
+                order = ("vaapi", "cuda")
+            for device in order:
+                if device not in available:
+                    continue
+                try:
+                    hw = HWAccel(device_type=device, allow_software_fallback=True)
+                    return self._av.open(str(path), hwaccel=hw)
+                except Exception:
+                    continue
+        except Exception:
+            pass
+        return self._av.open(str(path))
+
    def play(self, path):
        self.stop()
-        container = self._av.open(str(path))
+        container = self._open_container(path)
        self._container = container
        videos = [s for s in container.streams if s.type == "video"]
        if videos:
@@ -585,6 +644,15 @@ class AvEngine(_BaseEngine):
            )
        else:
            self._video_stream = None
+        if self._video_stream is not None:
+            try:
+                self._video_stream.thread_type = "AUTO"
+            except Exception:
+                pass
+            try:
+                self._video_stream.codec_context.thread_count = 0
+            except Exception:
+                pass
        self._audio_stream = next((s for s in container.streams if s.type == "audio"), None)
        self._gen += 1
        self._eof = False
@@ -594,22 +662,28 @@ class AvEngine(_BaseEngine):
        self._resampler = None
        self._audio_ok = False
        self._audio_broken = False
+        self._prerolling = True
+        self._pending_video.clear()
        if self._audio_stream is not None:
            try:
-                self._audio_stream_obj = self._sd.OutputStream(
-                    samplerate=self.AUDIO_RATE,
-                    channels=2,
-                    dtype="float32",
-                    callback=self._audio_callback,
-                )
-                self._audio_stream_obj.start()
+                kwargs = {
+                    "samplerate": self.AUDIO_RATE,
+                    "channels": 2,
+                    "dtype": "float32",
+                    "callback": self._audio_callback,
+                    "blocksize": 2048,
+                }
+                try:
+                    self._audio_stream_obj = self._sd.OutputStream(latency="high", **kwargs)
+                except TypeError:
+                    self._audio_stream_obj = self._sd.OutputStream(**kwargs)
                self._audio_ok = True
            except Exception:
                self._audio_stream_obj = None
        self._audio_written = 0
        self._clock_base = 0.0
        self._clock_started = time.monotonic()
-        self._clock_running = self._audio_stream_obj is None
+        self._clock_running = False
        self._stop_flag = threading.Event()
        self._thread = threading.Thread(target=self._decode_loop, daemon=True)
        self._thread.start()
@@ -657,13 +731,14 @@ class AvEngine(_BaseEngine):
            self._drain_queue(self._audio_queue)
            self._audio_leftover = None
            self._audio_written = int(target * self.AUDIO_RATE)
+            self._pending_video.clear()
+            self._prerolling = True
        self._clock_base = target
        self._clock_started = time.monotonic()
        self._ended = False
        if self._audio_stream_obj is not None:
            try:
                self._audio_stream_obj.stop()
-                self._audio_stream_obj.start()
            except Exception:
                pass
        if self._thread is None or not self._thread.is_alive():
@@ -677,11 +752,22 @@ class AvEngine(_BaseEngine):
    def get_time(self):
        if not self.is_active():
            return -1
-        if self._audio_stream_obj is not None:
+        if self._prerolling:
+            return int(self._seek_after * 1000.0)
+        if self._audio_stream_obj is not None and not self._prerolling:
            with self._lock:
                return int(self._audio_written * 1000.0 / self.AUDIO_RATE)
        return int(self._noaudio_pos() * 1000.0)

+    def set_display_size(self, width, height):
+        try:
+            width = int(width)
+            height = int(height)
+        except (TypeError, ValueError):
+            return
+        if width >= 2 and height >= 2:
+            self._display_size = (width, height)
+
    def _disable_audio(self, reason=""):
        """音频不可用时降级为无声播放，视频播放不受影响。"""
        stream = self._audio_stream_obj
@@ -735,7 +821,7 @@ class AvEngine(_BaseEngine):
        return False

    def get_frame(self):
-        if not self.is_active():
+        if not self.is_active() or self._prerolling:
            return None
        pos = self.get_time() / 1000.0
        latest = None
@@ -745,12 +831,78 @@ class AvEngine(_BaseEngine):
                if gen != self._gen:
                    self._video_deque.popleft()
                    continue
-                if secs > pos + 0.05:
+                if secs > pos + 0.02:
                    break
                latest = img
                self._video_deque.popleft()
        return latest

+    def _video_space(self):
+        with self._lock:
+            return len(self._video_deque) < self._video_deque_max
+
+    def _enqueue_video_frame(self, gen, secs, frame):
+        if gen != self._gen:
+            return
+        img = self._frame_to_image(frame)
+        if img is None:
+            return
+        with self._lock:
+            if gen != self._gen:
+                return
+            if len(self._video_deque) >= self._video_deque_max:
+                return
+            self._video_deque.append((gen, secs, img))
+
+    def _frame_to_image(self, frame):
+        try:
+            fw = int(getattr(frame, "width", 0) or 0)
+            fh = int(getattr(frame, "height", 0) or 0)
+            if fw < 1 or fh < 1:
+                return None
+            tw, th = fw, fh
+            display = self._display_size
+            if display:
+                dw, dh = display
+                if dw >= 2 and dh >= 2:
+                    scale = min(dw / fw, dh / fh, 1.0)
+                    tw = max(2, int(fw * scale) // 2 * 2)
+                    th = max(2, int(fh * scale) // 2 * 2)
+            if tw > 1920:
+                th = max(2, int(th * 1920 / tw) // 2 * 2)
+                tw = 1920
+            fmt = getattr(getattr(frame, "format", None), "name", "") or ""
+            if tw != fw or th != fh or fmt != "rgb24":
+                frame = frame.reformat(width=tw, height=th, format="rgb24")
+            return frame.to_image()
+        except Exception:
+            try:
+                return frame.to_image()
+            except Exception:
+                return None
+
+    def _maybe_finish_preroll(self):
+        if not self._prerolling or self._stop_flag.is_set() or self._paused:
+            return
+        with self._lock:
+            video_ready = self._video_stream is None or len(self._video_deque) >= 6
+        audio_ready = (not self._audio_ok) or self._audio_queue.qsize() >= 12
+        if not video_ready or not audio_ready:
+            return
+        self._prerolling = False
+        self._clock_base = self._seek_after
+        self._clock_started = time.monotonic()
+        self._audio_written = int(self._seek_after * self.AUDIO_RATE)
+        if self._audio_stream_obj is not None:
+            try:
+                self._audio_stream_obj.start()
+            except Exception:
+                self._clock_running = True
+                return
+            self._clock_running = False
+        else:
+            self._clock_running = True
+
    def poll_events(self):
        events = super().poll_events()
        if self._audio_broken and self._audio_stream_obj is not None:
@@ -770,6 +922,37 @@ class AvEngine(_BaseEngine):
    def release(self):
        self.stop()

+    def _decode_video_packet(self, packet, gen):
+        video = self._video_stream
+        if video is None:
+            return
+        try:
+            frames = packet.decode()
+        except Exception:
+            return
+        for frame in frames:
+            if self._stop_flag.is_set() or gen != self._gen:
+                return
+            if frame.pts is None:
+                continue
+            secs = float(frame.pts * video.time_base)
+            if secs + 0.05 < self._seek_after:
+                continue
+            while not self._stop_flag.is_set() and gen == self._gen:
+                if self._paused:
+                    time.sleep(0.01)
+                    continue
+                if self._video_space():
+                    self._enqueue_video_frame(gen, secs, frame)
+                    break
+                time.sleep(0.003)
+
+    def _drain_pending_video(self, gen):
+        while self._pending_video and not self._stop_flag.is_set() and gen == self._gen:
+            if not self._video_space():
+                return
+            self._decode_video_packet(self._pending_video.popleft(), gen)
+
    def _decode_loop(self):
        try:
            container = self._container
@@ -778,10 +961,15 @@ class AvEngine(_BaseEngine):
            streams = [s for s in (video, audio) if s is not None]
            demux = container.demux(*streams)
            while not self._stop_flag.is_set():
+                if self._paused and self._seek_request is None:
+                    time.sleep(0.02)
+                    continue
                if self._seek_request is not None:
                    with self._lock:
                        target = self._seek_request
                        self._seek_request = None
+                    self._pending_video.clear()
+                    self._prerolling = True
                    seek_stream = video if video is not None else audio
                    if seek_stream is not None:
                        offset = int(round(target / float(seek_stream.time_base)))
@@ -793,9 +981,19 @@ class AvEngine(_BaseEngine):
                    self._resampler = None
                    continue
                gen = self._gen
+                self._maybe_finish_preroll()
+                audio_low = self._audio_ok and self._audio_queue.qsize() < 12
+                if not audio_low:
+                    self._drain_pending_video(gen)
                try:
                    packet = next(demux)
                except StopIteration:
+                    while self._pending_video and not self._stop_flag.is_set() and gen == self._gen:
+                        if self._video_space():
+                            self._decode_video_packet(self._pending_video.popleft(), gen)
+                        else:
+                            time.sleep(0.005)
+                        self._maybe_finish_preroll()
                    self._eof = True
                    break
                except Exception:
@@ -804,28 +1002,22 @@ class AvEngine(_BaseEngine):
                if self._stop_flag.is_set():
                    break
                if packet.stream.type == "video" and video is not None and packet.size:
-                    try:
-                        frames = packet.decode()
-                    except Exception:
-                        continue
-                    for frame in frames:
-                        if self._stop_flag.is_set():
-                            break
-                        if frame.pts is None:
-                            continue
-                        secs = float(frame.pts * video.time_base)
-                        if secs + 0.05 < self._seek_after:
-                            continue
-                        try:
-                            img = frame.to_image()
-                        except Exception:
-                            continue
-                        while not self._stop_flag.is_set():
-                            with self._lock:
-                                if len(self._video_deque) < self._video_deque_max:
-                                    self._video_deque.append((gen, secs, img))
-                                    break
-                            time.sleep(0.005)
+                    if self._video_space() and not self._pending_video:
+                        self._decode_video_packet(packet, gen)
+                    elif len(self._pending_video) < 90:
+                        self._pending_video.append(packet)
+                    else:
+                        while (
+                            not self._stop_flag.is_set()
+                            and gen == self._gen
+                            and len(self._pending_video) >= 90
+                        ):
+                            if self._video_space():
+                                self._decode_video_packet(self._pending_video.popleft(), gen)
+                            else:
+                                time.sleep(0.005)
+                        if not self._stop_flag.is_set() and gen == self._gen:
+                            self._pending_video.append(packet)
                elif packet.stream.type == "audio" and audio is not None and packet.size:
                    if not self._audio_ok:
                        continue
@@ -835,6 +1027,7 @@ class AvEngine(_BaseEngine):
                        self._disable_audio("音频解码出错（%s）" % exc)
            if self._resampler is not None and not self._stop_flag.is_set():
                self._flush_resampler()
+            self._maybe_finish_preroll()
        except Exception as exc:
            self._eof = True
            print("解码线程异常退出：", exc)
@@ -1044,6 +1237,14 @@ class MediaPlayerApp(tk.Tk):
        self._translation_error = ""
        self._subtitle_srt_key = None
        self._overlay_key = None
+        self._subtitle_english = ""
+        self._subtitle_chinese = ""
+        self._last_video_frame = None
+        self._subtitle_fonts = {}
+        self._canvas_image_id = None
+        self._subtitle_bar_cache = None
+        self._last_play_label = None
+        self._last_time_label = None

        self.engine = self._create_engine()
        if self.engine is None:
@@ -1148,7 +1349,7 @@ class MediaPlayerApp(tk.Tk):
            text="",
            fg="#ffffff",
            bg="#000000",
-            font=("Helvetica", 16, "bold"),
+            font=("Helvetica", SUBTITLE_EN_FONT_SIZE, "bold"),
            wraplength=720,
            justify="center",
        )
@@ -1158,7 +1359,7 @@ class MediaPlayerApp(tk.Tk):
            text="",
            fg="#ffd54a",
            bg="#000000",
-            font=("Helvetica", 14),
+            font=("Helvetica", SUBTITLE_ZH_FONT_SIZE),
            wraplength=720,
            justify="center",
        )
@@ -1259,6 +1460,15 @@ class MediaPlayerApp(tk.Tk):
            takefocus=0,
        )
        self.btn_ai_explain.pack(side="left", padx=(12, 0))
+        self.btn_export_subtitles = ttk.Button(
+            controls,
+            text="导出字幕",
+            command=self.export_subtitles,
+            takefocus=0,
+            state="disabled",
+        )
+        self.btn_export_subtitles.pack(side="left", padx=(12, 0))
+        self.btn_export_subtitles.bind("<space>", self._on_space)
        self.sentence_var = tk.StringVar(value="")
        self.sentence_label = ttk.Label(
            controls,
@@ -1394,24 +1604,37 @@ class MediaPlayerApp(tk.Tk):
                    self._on_media_end()
                elif event == "error":
                    self.status_var.set("无法播放该文件，请检查文件格式或 VLC 是否已安装")
+            canvas = getattr(self, "video_canvas", None)
+            if canvas is not None:
+                setter = getattr(self.engine, "set_display_size", None)
+                if setter is not None:
+                    setter(canvas.winfo_width(), canvas.winfo_height())
            img = self.engine.get_frame()
            if img is not None:
                self._show_frame(img)
            pos = self.engine.get_time()
            length = self.engine.get_length()
            if pos >= 0 and not self._seeking:
-                self.time_var.set(f"{fmt_time(pos)} / {fmt_time(length)}")
+                time_label = f"{fmt_time(pos)} / {fmt_time(length)}"
+                if time_label != self._last_time_label:
+                    self._last_time_label = time_label
+                    self.time_var.set(time_label)
                if length > 0:
                    self.seekbar.set_frac(pos / length)
                sentence = self._current_sentence()
-                text = str(sentence.get("text") or "").strip() if sentence else ""
-                self.sentence_var.set(text)
+                sentence_text = str(sentence.get("text") or "").strip() if sentence else ""
+                if sentence_text != self.sentence_var.get():
+                    self.sentence_var.set(sentence_text)
            self._update_on_screen_subtitles()
            playing = self.engine.is_playing()
-            self.btn_play.config(text="暂停" if playing else "播放")
-        self.after(33, self._tick)
+            play_label = "暂停" if playing else "播放"
+            if play_label != self._last_play_label:
+                self._last_play_label = play_label
+                self.btn_play.config(text=play_label)
+        software_video = isinstance(self.engine, AvEngine) and self.engine.is_playing()
+        self.after(16 if software_video else 50, self._tick)

-    def _show_frame(self, img):
+    def _show_frame(self, img, store=True):
        if ImageTk is None:
            return
        canvas = getattr(self, "video_canvas", None)
@@ -1428,11 +1651,17 @@ class MediaPlayerApp(tk.Tk):
        size = (max(1, int(iw * scale)), max(1, int(ih * scale)))
        if size != img.size:
            img = img.resize(size, PILImage.Resampling.BILINEAR)
-        self._photo = ImageTk.PhotoImage(img)
-        canvas.delete("all")
-        canvas.create_image(width // 2, height // 2, image=self._photo, anchor="center")
-        if getattr(self, "subtitle_overlay", None) is not None:
-            self.subtitle_overlay.lift()
+        if store:
+            self._last_video_frame = img
+        display = self._compose_subtitles(img)
+        self._photo = ImageTk.PhotoImage(display)
+        x = width // 2
+        y = height // 2
+        if self._canvas_image_id is None:
+            self._canvas_image_id = canvas.create_image(x, y, image=self._photo, anchor="center")
+        else:
+            canvas.coords(self._canvas_image_id, x, y)
+            canvas.itemconfig(self._canvas_image_id, image=self._photo)

    def open_files(self):
        filetypes = [
@@ -1629,6 +1858,11 @@ class MediaPlayerApp(tk.Tk):
        if canvas is not None:
            canvas.delete("all")
        self._photo = None
+        self._canvas_image_id = None
+        self._last_video_frame = None
+        self._subtitle_bar_cache = None
+        self._subtitle_english = ""
+        self._subtitle_chinese = ""
        self.video_hint.place(relx=0.5, rely=0.5, anchor="center")
        self._update_sentence_controls()
        self._update_status()
@@ -1826,6 +2060,9 @@ class MediaPlayerApp(tk.Tk):
                state="normal",
                text="重新生成" if has_boundaries else "生成句边界",
            )
+        export_btn = getattr(self, "btn_export_subtitles", None)
+        if export_btn is not None:
+            export_btn.config(state="normal" if has_boundaries else "disabled")

    def _set_progress(self, value=None, message=None, indeterminate=False):
        if not hasattr(self, "boundary_progress"):
@@ -1877,6 +2114,68 @@ class MediaPlayerApp(tk.Tk):
        self._update_on_screen_subtitles()
        self._sync_vlc_subtitles(force=True)

+    def export_subtitles(self):
+        path = self._current_path()
+        if path is None:
+            messagebox.showinfo("导出字幕", "请先打开并选择一个媒体文件。")
+            return
+        sentences = (self._boundaries.get(path) or {}).get("sentences") or []
+        if not sentences:
+            messagebox.showinfo("导出字幕", "请先生成句边界后再导出字幕。")
+            return
+        english_count = sum(1 for sentence in sentences if str(sentence.get("text") or "").strip())
+        chinese_count = sum(1 for sentence in sentences if str(sentence.get("zh_text") or "").strip())
+        if english_count == 0 and chinese_count == 0:
+            messagebox.showinfo("导出字幕", "当前句边界没有可导出的字幕文本。")
+            return
+        include_chinese = chinese_count > 0
+        if not include_chinese:
+            if not messagebox.askyesno(
+                "导出字幕",
+                "还没有中文翻译，是否只导出英文字幕？\n可先打开“中文字幕”等待翻译完成后再导出双语字幕。",
+            ):
+                return
+        media = Path(path)
+        suffix = "en-zh" if include_chinese else "en"
+        default_name = f"{media.stem}.{suffix}.ass"
+        destination = filedialog.asksaveasfilename(
+            title="导出中英文字幕",
+            defaultextension=".ass",
+            initialdir=str(media.parent),
+            initialfile=default_name,
+            filetypes=[
+                ("ASS 字幕（推荐，QQPlayer 更清晰）", "*.ass"),
+                ("SubRip 字幕", "*.srt"),
+                ("所有文件", "*"),
+            ],
+        )
+        if not destination:
+            return
+        dest = Path(destination)
+        if dest.suffix.lower() == ".srt":
+            content = self._build_srt_content(sentences, include_chinese=include_chinese)
+        else:
+            if dest.suffix.lower() not in {".ass", ".ssa"}:
+                dest = dest.with_suffix(".ass")
+            content = self._build_ass_content(
+                sentences,
+                include_chinese=include_chinese,
+                title=media.stem,
+            )
+        if not content.strip():
+            messagebox.showinfo("导出字幕", "没有可写入字幕文件的内容。")
+            return
+        try:
+            dest.write_text(content, encoding="utf-8-sig")
+        except Exception as exc:
+            messagebox.showerror("导出字幕", f"保存失败：{exc}")
+            return
+        destination = str(dest)
+        note = ""
+        if include_chinese and chinese_count < english_count:
+            note = f"（其中 {chinese_count}/{english_count} 句已有中文）"
+        self.status_var.set(f"字幕已导出：{Path(destination).name}{note}")
+
    def generate_sentence_boundaries(self):
        path = self._current_path()
        if path is None:
@@ -2213,6 +2512,139 @@ class MediaPlayerApp(tk.Tk):
            detail = str(detail)
        return detail if len(detail) <= 300 else detail[:297] + "..."

+    def _subtitle_font(self, size, bold=False):
+        key = (size, bold)
+        cached = self._subtitle_fonts.get(key)
+        if cached is not None:
+            return cached
+        if ImageFont is None:
+            return None
+        candidates = [
+            "/System/Library/Fonts/PingFang.ttc",
+            "/System/Library/Fonts/STHeiti Light.ttc",
+            "/System/Library/Fonts/Hiragino Sans GB.ttc",
+            "/Library/Fonts/Arial Unicode.ttf",
+            "C:/Windows/Fonts/msyhbd.ttc" if bold else "C:/Windows/Fonts/msyh.ttc",
+            "C:/Windows/Fonts/msyh.ttc",
+            "/usr/share/fonts/opentype/noto/NotoSansCJK-Regular.ttc",
+            "/usr/share/fonts/truetype/noto/NotoSansCJK-Regular.ttc",
+            "/usr/share/fonts/truetype/wqy/wqy-microhei.ttc",
+        ]
+        font = None
+        for path in candidates:
+            if not path or not Path(path).exists():
+                continue
+            try:
+                font = ImageFont.truetype(path, size=size)
+                break
+            except Exception:
+                continue
+        if font is None:
+            try:
+                font = ImageFont.load_default()
+            except Exception:
+                font = None
+        self._subtitle_fonts[key] = font
+        return font
+
+    @staticmethod
+    def _wrap_subtitle_text(draw, text, font, max_width):
+        if not text:
+            return []
+        lines = []
+        for paragraph in str(text).splitlines() or [text]:
+            current = ""
+            for char in paragraph:
+                trial = current + char
+                bbox = draw.textbbox((0, 0), trial, font=font, stroke_width=2)
+                if bbox[2] - bbox[0] <= max_width or not current:
+                    current = trial
+                else:
+                    lines.append(current)
+                    current = char
+            if current:
+                lines.append(current)
+        return lines
+
+    def _compose_subtitles(self, img):
+        english = getattr(self, "_subtitle_english", "") or ""
+        chinese = getattr(self, "_subtitle_chinese", "") or ""
+        if (not english and not chinese) or PILImage is None or ImageDraw is None:
+            return img
+        overlay, bar_top = self._subtitle_overlay_bar(english, chinese, img.width, img.height)
+        if overlay is None:
+            return img
+        rgb = img if img.mode == "RGB" else img.convert("RGB")
+        out = rgb.copy()
+        region = out.crop((0, bar_top, rgb.width, rgb.height)).convert("RGBA")
+        composed = PILImage.alpha_composite(region, overlay)
+        out.paste(composed.convert("RGB"), (0, bar_top))
+        return out
+
+    def _subtitle_overlay_bar(self, english, chinese, width, height):
+        key = (english, chinese, width, height)
+        cached = self._subtitle_bar_cache
+        if cached and cached[0] == key:
+            return cached[1], cached[2]
+        en_font = self._subtitle_font(SUBTITLE_EN_FONT_SIZE, bold=True)
+        zh_font = self._subtitle_font(SUBTITLE_ZH_FONT_SIZE, bold=False)
+        if en_font is None or zh_font is None:
+            return None, 0
+        measure = PILImage.new("RGBA", (max(1, width), 8), (0, 0, 0, 0))
+        draw = ImageDraw.Draw(measure)
+        max_width = max(40, int(width * 0.90))
+        en_lines = self._wrap_subtitle_text(draw, english, en_font, max_width)
+        zh_lines = self._wrap_subtitle_text(draw, chinese, zh_font, max_width)
+        if not en_lines and not zh_lines:
+            self._subtitle_bar_cache = (key, None, 0)
+            return None, 0
+
+        def line_height(line, font):
+            bbox = draw.textbbox((0, 0), line, font=font, stroke_width=2)
+            return max(1, bbox[3] - bbox[1])
+
+        gap = 8
+        padding_y = 14
+        content_h = 0
+        for line in en_lines:
+            content_h += line_height(line, en_font) + gap
+        for line in zh_lines:
+            content_h += line_height(line, zh_font) + gap
+        if content_h:
+            content_h -= gap
+        bar_h = min(height, content_h + padding_y * 2)
+        bar_top = max(0, height - bar_h - max(8, int(height * 0.03)))
+        overlay = PILImage.new("RGBA", (width, height - bar_top), (0, 0, 0, 0))
+        draw = ImageDraw.Draw(overlay)
+        draw.rectangle((0, 0, width, overlay.height), fill=(0, 0, 0, SUBTITLE_BG_ALPHA))
+        y = padding_y
+        for line in en_lines:
+            bbox = draw.textbbox((0, 0), line, font=en_font, stroke_width=2)
+            x = max(0, (width - (bbox[2] - bbox[0])) // 2)
+            draw.text(
+                (x, y),
+                line,
+                font=en_font,
+                fill=(255, 255, 255, 255),
+                stroke_width=2,
+                stroke_fill=(0, 0, 0, 255),
+            )
+            y += line_height(line, en_font) + gap
+        for line in zh_lines:
+            bbox = draw.textbbox((0, 0), line, font=zh_font, stroke_width=2)
+            x = max(0, (width - (bbox[2] - bbox[0])) // 2)
+            draw.text(
+                (x, y),
+                line,
+                font=zh_font,
+                fill=(255, 213, 74, 255),
+                stroke_width=2,
+                stroke_fill=(0, 0, 0, 255),
+            )
+            y += line_height(line, zh_font) + gap
+        self._subtitle_bar_cache = (key, overlay, bar_top)
+        return overlay, bar_top
+
    def _on_video_resize(self, event):
        if event.widget is not getattr(self, "video_frame", None):
            return
@@ -2251,10 +2683,22 @@ class MediaPlayerApp(tk.Tk):
                    chinese = "正在翻译中文字幕…"
                else:
                    chinese = "暂无中文字幕"
+        self._subtitle_english = english
+        self._subtitle_chinese = chinese
        key = (english, chinese, bool(self.show_chinese_subtitles.get()))
-        if key == self._overlay_key:
-            return
+        changed = key != self._overlay_key
        self._overlay_key = key
+        canvas = getattr(self, "video_canvas", None)
+        if canvas is not None and self._last_video_frame is not None:
+            try:
+                overlay.place_forget()
+            except tk.TclError:
+                pass
+            if changed:
+                self._show_frame(self._last_video_frame, store=False)
+            return
+        if not changed:
+            return
        try:
            self.subtitle_en.configure(text=english)
            if chinese:
@@ -2290,6 +2734,45 @@ class MediaPlayerApp(tk.Tk):
            number += 1
        return "\n\n".join(blocks) + ("\n" if blocks else "")

+    def _build_ass_content(self, sentences, include_chinese: bool, title: str = "") -> str:
+        events = []
+        for sentence in sentences:
+            english = str(sentence.get("text") or "").strip()
+            chinese = str(sentence.get("zh_text") or "").strip() if include_chinese else ""
+            if not english and not chinese:
+                continue
+            start = _ass_timestamp(sentence.get("start_ms") or 0)
+            end = _ass_timestamp(sentence.get("end_ms") or 0)
+            if english and chinese:
+                text = "{{\\an2\\fnMicrosoft YaHei\\b1\\fs60}}{}\\N{{\\b0\\fs48}}{}".format(
+                    _escape_ass_text(english),
+                    _escape_ass_text(chinese),
+                )
+            elif english:
+                text = "{{\\an2\\fnMicrosoft YaHei\\b1\\fs60}}{}".format(_escape_ass_text(english))
+            else:
+                text = "{{\\an2\\fnMicrosoft YaHei\\b0\\fs48}}{}".format(_escape_ass_text(chinese))
+            events.append("Dialogue: 0,{},{},Default,,0,0,0,,{}".format(start, end, text))
+        safe_title = (title or "Subtitles").replace("\r", " ").replace("\n", " ")
+        header_lines = [
+            "[Script Info]",
+            "Title: " + safe_title,
+            "ScriptType: v4.00+",
+            "WrapStyle: 0",
+            "ScaledBorderAndShadow: yes",
+            "Collisions: Normal",
+            "PlayResX: 1920",
+            "PlayResY: 1080",
+            "",
+            "[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: Default,Microsoft YaHei,52,&H00FFFFFF,&H000000FF,&H00000000,&H00000000,-1,0,0,0,100,100,0,0,1,3,0,2,80,80,50,1",
+            "",
+            "[Events]",
+            "Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text",
+        ]
+        return "\r\n".join(header_lines + events) + "\r\n"
+
    def _sync_vlc_subtitles(self, force=False):
        if not isinstance(self.engine, VlcEngine):
            return
--- a/sentence_api/README.md
+++ b/sentence_api/README.md
@@ -59,6 +59,7 @@ POST   /api/v1/videos/{sha256}/sentences/{index}/assessments
 POST   /api/v1/admin/videos
 PUT    /api/v1/admin/videos/raw
 POST   /api/v1/admin/videos/{sha256}/process
+POST   /api/v1/admin/videos/{sha256}/repair-gaps
 GET    /api/v1/admin/videos/{sha256}/subtitle-translation
 POST   /api/v1/admin/videos/{sha256}/subtitle-translation
 PUT    /api/v1/admin/videos/{sha256}/sentences/{index}
--- a/sentence_api/main.py
+++ b/sentence_api/main.py
@@ -43,6 +43,8 @@ from .models import (
    CourseSummary,
    CourseTitleUpdate,
    SentenceBoundaryAdjust,
+    SentenceGapRepairRequest,
+    SentenceGapRepairResponse,
    SentenceBoundary,
    SentenceBoundaryDocument,
    SentenceExplanationRequest,
@@ -688,6 +690,34 @@ def create_app(
        background_tasks.add_task(_process_safely, processor, video_hash)
        return {"video_hash": video_hash.lower(), "status": "processing_queued"}

+    @application.post(
+        "/api/v1/admin/videos/{video_hash}/repair-gaps",
+        response_model=SentenceGapRepairResponse,
+        dependencies=[Depends(require_admin)],
+    )
+    async def repair_sentence_gaps(
+        payload: Optional[SentenceGapRepairRequest] = None,
+        video_hash: str = SHA256_PATH,
+    ) -> SentenceGapRepairResponse:
+        request = payload or SentenceGapRepairRequest()
+        try:
+            result = await run_in_threadpool(
+                processor.repair_gaps,
+                video_hash,
+                request.min_gap_ms,
+            )
+        except KeyError:
+            raise HTTPException(status_code=404, detail="Video was not found.") from None
+        except FileNotFoundError as exc:
+            raise HTTPException(status_code=404, detail=str(exc)) from exc
+        except ValueError as exc:
+            raise HTTPException(status_code=400, detail=str(exc)) from exc
+        except RuntimeError as exc:
+            raise HTTPException(status_code=503, detail=str(exc)) from exc
+        if result["inserted_count"]:
+            application.state.subtitle_translations.start_missing(video_hash)
+        return SentenceGapRepairResponse(video_hash=video_hash.lower(), **result)
+
    @application.get(
        "/api/v1/admin/videos/{video_hash}/subtitle-translation",
        response_model=AdminSubtitleTranslationResponse,
--- a/sentence_api/models.py
+++ b/sentence_api/models.py
@@ -185,6 +185,23 @@ class SentenceBoundaryAdjust(BaseModel):
    delta_ms: int = Field(ge=-10_000, le=10_000)


+class SentenceGapRepairRequest(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+
+    min_gap_ms: int = Field(default=8000, ge=2000, le=180_000)
+
+
+class SentenceGapRepairResponse(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+
+    video_hash: str
+    min_gap_ms: int = Field(ge=1)
+    gap_count: int = Field(ge=0)
+    transcribed_gaps: int = Field(ge=0)
+    inserted_count: int = Field(ge=0)
+    sentence_count: int = Field(ge=0)
+
+
 class TextSubstitution(BaseModel):
    expected: str
    actual: str
--- a/sentence_api/processing.py
+++ b/sentence_api/processing.py
@@ -4,7 +4,7 @@ import subprocess
 import tempfile
 import uuid
 from pathlib import Path
-from typing import Any, Dict, List, Optional
+from typing import Any, Dict, List, Optional, Sequence, Tuple

 from .audio_metrics import (
    AudioAnalysisError,
@@ -29,6 +29,10 @@ from .transcription import (
 logger = logging.getLogger(__name__)
 MOSS_ALGORITHM_VERSION = "moss-punctuation-v4"
 SILENCE_ALGORITHM_VERSION = "silence-rms-v1"
+GAP_REPAIR_MIN_MS = 8_000
+GAP_REPAIR_INSET_MS = 150
+GAP_REPAIR_MIN_SPEECH_MS = 400
+GAP_REPAIR_MIN_SENTENCE_MS = 100
 _CUES_ID = b"\x1e\x53\xb6\x80"
 _CLUSTER_ID = b"\x1f\x43\xb6\x75"
 _HEADER_SCAN_SIZE = 64 * 1024
@@ -173,6 +177,106 @@ class VideoProcessor:
        )
        self.repository.mark_oss_uploaded(document.video_hash, remote_url)

+    def repair_gaps(
+        self,
+        video_hash: str,
+        min_gap_ms: int = GAP_REPAIR_MIN_MS,
+    ) -> Dict[str, int]:
+        """Re-transcribe long unsentenced gaps without replacing existing cues."""
+        if min_gap_ms < 1:
+            raise ValueError("min_gap_ms must be positive")
+        if not self.transcriber.available:
+            raise RuntimeError("MOSS transcription is not configured on this server.")
+        video = self.repository.get_video(video_hash)
+        if video is None:
+            raise KeyError(video_hash)
+        document = self.repository.get_document(video_hash)
+        if document is None or not document.sentences:
+            raise ValueError("Sentence boundaries are not available for this video.")
+        media_path = self.settings.videos_dir / video["stored_filename"]
+        if not media_path.is_file():
+            raise FileNotFoundError(f"Stored video is missing: {media_path.name}")
+
+        gaps = find_sentence_gaps(document, min_gap_ms)
+        inserted: List[SentenceBoundary] = []
+        transcribed_gaps = 0
+        if gaps:
+            language = video.get("language")
+            with tempfile.TemporaryDirectory(prefix="gap-repair-") as temp_dir:
+                for gap_index, (raw_start, raw_end) in enumerate(gaps):
+                    clipped = _inset_gap(raw_start, raw_end, document.duration_ms)
+                    if clipped is None:
+                        continue
+                    start_ms, end_ms = clipped
+                    chunk_path = Path(temp_dir) / f"gap-{gap_index}.wav"
+                    try:
+                        extract_audio_segment(
+                            media_path,
+                            chunk_path,
+                            start_ms=start_ms,
+                            duration_ms=end_ms - start_ms,
+                        )
+                        samples, sample_rate = decode_audio_mono(chunk_path)
+                        metrics = analyze_samples(samples, sample_rate)
+                    except (AudioAnalysisError, RuntimeError) as exc:
+                        logger.info(
+                            "Skipping sentence gap %s-%sms: %s",
+                            start_ms,
+                            end_ms,
+                            exc,
+                        )
+                        continue
+                    if metrics.speech_duration_ms < GAP_REPAIR_MIN_SPEECH_MS:
+                        continue
+                    try:
+                        transcript = self.transcriber.transcribe(chunk_path, language)
+                    except Exception as exc:
+                        logger.warning(
+                            "Gap transcription failed for %s %s-%sms: %s",
+                            video_hash,
+                            start_ms,
+                            end_ms,
+                            exc,
+                        )
+                        continue
+                    gap_document = document_from_transcript(
+                        video_hash=video_hash,
+                        duration_ms=end_ms - start_ms,
+                        transcript=transcript,
+                        language=language,
+                        audio_path=chunk_path,
+                        end_padding_ms=self.settings.moss_end_padding_ms,
+                    )
+                    shifted = _shift_gap_sentences(
+                        gap_document.sentences,
+                        offset_ms=start_ms,
+                        limit_end_ms=end_ms,
+                    )
+                    if not shifted:
+                        continue
+                    transcribed_gaps += 1
+                    inserted.extend(shifted)
+
+        if not inserted:
+            return {
+                "min_gap_ms": min_gap_ms,
+                "gap_count": len(gaps),
+                "transcribed_gaps": transcribed_gaps,
+                "inserted_count": 0,
+                "sentence_count": len(document.sentences),
+            }
+
+        merged = _merge_sentence_lists(document.sentences, inserted)
+        updated = document.model_copy(update={"sentences": merged})
+        saved = self.repository.replace_sentences(updated)
+        return {
+            "min_gap_ms": min_gap_ms,
+            "gap_count": len(gaps),
+            "transcribed_gaps": transcribed_gaps,
+            "inserted_count": len(saved.sentences) - len(document.sentences),
+            "sentence_count": len(saved.sentences),
+        }
+

 def extract_audio(media_path: Path, output_path: Path) -> None:
    ffmpeg = shutil.which("ffmpeg")
@@ -241,6 +345,82 @@ def extract_audio_segment(
        raise RuntimeError(f"Could not extract sentence audio: {message[-2000:]}")


+def find_sentence_gaps(
+    document: SentenceBoundaryDocument,
+    min_gap_ms: int = GAP_REPAIR_MIN_MS,
+) -> List[Tuple[int, int]]:
+    """Return [start_ms, end_ms) ranges that are missing sentence coverage."""
+    if min_gap_ms < 1:
+        raise ValueError("min_gap_ms must be positive")
+    gaps: List[Tuple[int, int]] = []
+    cursor = 0
+    for sentence in document.sentences:
+        if sentence.start_ms - cursor >= min_gap_ms:
+            gaps.append((cursor, sentence.start_ms))
+        cursor = max(cursor, sentence.end_ms)
+    if document.duration_ms - cursor >= min_gap_ms:
+        gaps.append((cursor, document.duration_ms))
+    return gaps
+
+
+def _inset_gap(
+    start_ms: int,
+    end_ms: int,
+    duration_ms: int,
+    inset_ms: int = GAP_REPAIR_INSET_MS,
+) -> Optional[Tuple[int, int]]:
+    start = start_ms + (inset_ms if start_ms > 0 else 0)
+    end = end_ms - (inset_ms if end_ms < duration_ms else 0)
+    if end - start < GAP_REPAIR_MIN_SPEECH_MS:
+        return None
+    return start, end
+
+
+def _shift_gap_sentences(
+    sentences: Sequence[SentenceBoundary],
+    *,
+    offset_ms: int,
+    limit_end_ms: int,
+) -> List[SentenceBoundary]:
+    shifted: List[SentenceBoundary] = []
+    previous_end = offset_ms
+    for sentence in sentences:
+        start_ms = max(previous_end, sentence.start_ms + offset_ms)
+        end_ms = min(limit_end_ms, sentence.end_ms + offset_ms)
+        text = (sentence.text or "").strip()
+        if not text or end_ms - start_ms < GAP_REPAIR_MIN_SENTENCE_MS:
+            continue
+        shifted.append(
+            sentence.model_copy(
+                update={
+                    "index": len(shifted),
+                    "start_ms": start_ms,
+                    "end_ms": end_ms,
+                    "text": text,
+                    "zh_text": None,
+                }
+            )
+        )
+        previous_end = end_ms
+    return shifted
+
+
+def _merge_sentence_lists(
+    existing: Sequence[SentenceBoundary],
+    inserted: Sequence[SentenceBoundary],
+) -> List[SentenceBoundary]:
+    combined = [*existing, *inserted]
+    combined.sort(key=lambda sentence: (sentence.start_ms, sentence.end_ms))
+    merged: List[SentenceBoundary] = []
+    previous_end = 0
+    for sentence in combined:
+        if sentence.start_ms < previous_end:
+            continue
+        merged.append(sentence.model_copy(update={"index": len(merged)}))
+        previous_end = sentence.end_ms
+    return merged
+
+
 def split_sentence_text(
    *,
    transcriber: Transcriber,
--- a/sentence_api/repository.py
+++ b/sentence_api/repository.py
@@ -544,6 +544,53 @@ class VideoRepository:
            sentences=[_sentence_from_row(row) for row in rows],
        )

+    def replace_sentences(
+        self,
+        document: SentenceBoundaryDocument,
+    ) -> SentenceBoundaryDocument:
+        """Replace stored sentences while preserving video status and translations."""
+        normalized_hash = normalize_video_hash(document.video_hash)
+        with self._connect() as connection:
+            existing = connection.execute(
+                "SELECT video_hash FROM videos WHERE video_hash = ?",
+                (normalized_hash,),
+            ).fetchone()
+            if existing is None:
+                raise KeyError(normalized_hash)
+            connection.execute(
+                "DELETE FROM sentences WHERE video_hash = ?",
+                (normalized_hash,),
+            )
+            connection.executemany(
+                """
+                INSERT INTO sentences (
+                    video_hash, sentence_index, start_ms, end_ms, text,
+                    language, zh_text, reference_speech_duration_ms
+                ) VALUES (?, ?, ?, ?, ?, ?, ?, ?)
+                """,
+                [
+                    (
+                        normalized_hash,
+                        sentence.index,
+                        sentence.start_ms,
+                        sentence.end_ms,
+                        sentence.text,
+                        sentence.language,
+                        sentence.zh_text,
+                        sentence.reference_speech_duration_ms,
+                    )
+                    for sentence in document.sentences
+                ],
+            )
+            connection.execute(
+                "UPDATE videos SET updated_at = ? WHERE video_hash = ?",
+                (utc_now(), normalized_hash),
+            )
+        saved = self.get_document(normalized_hash)
+        if saved is None:
+            raise KeyError(normalized_hash)
+        return saved
+
    def update_sentence_text(
        self,
        video_hash: str,
--- a/sentence_api/static/admin.css
+++ b/sentence_api/static/admin.css
@@ -81,7 +81,7 @@ table { width: 100%; border-collapse: collapse; font-size: 13px; }
 th, td { padding: 10px 12px; text-align: left; border-bottom: 1px solid #e3e7ea; vertical-align: middle; }
 th { position: sticky; top: 0; z-index: 1; color: #44515b; background: #edf1f3; font-weight: 600; }
 tr:last-child td { border-bottom: 0; }
-.actions-column { min-width: 280px; }
+.actions-column { min-width: 340px; }
 .actions { display: flex; gap: 6px; white-space: nowrap; }
 .actions button, .actions a { min-height: 30px; padding: 5px 9px; font-size: 12px; }
 .actions a { display: inline-flex; align-items: center; border: 1px solid #aab4bc; border-radius: 4px; color: #26323c; text-decoration: none; }
@@ -103,6 +103,8 @@ dialog {
 dialog::backdrop { background: rgb(20 25 28 / 55%); }
 .dialog-heading { padding: 16px 18px; display: flex; justify-content: space-between; align-items: center; border-bottom: 1px solid #dce1e5; }
 .dialog-heading span { font-size: 12px; color: #68747d; }
+.dialog-heading-actions { display: flex; align-items: center; gap: 8px; }
+.gap-row td { background: #fff8ee; color: #9a5b12; font-style: italic; }
 .sentence-scroll { max-height: calc(100vh - 120px); overflow: auto; }
 .sentence-scroll textarea { width: min(600px, 45vw); min-width: 260px; min-height: 58px; resize: vertical; padding: 7px; border: 1px solid #b8c0c7; border-radius: 3px; }
 .sentence-scroll select { min-width: 90px; }
--- a/sentence_api/static/admin.html
+++ b/sentence_api/static/admin.html
@@ -122,7 +122,10 @@
        <h2 id="sentence-title">句子文本</h2>
        <span id="sentence-meta"></span>
      </div>
-      <button id="close-dialog" class="icon-button" type="button" aria-label="关闭">X</button>
+      <div class="dialog-heading-actions">
+        <button id="repair-gaps" type="button">修复空白</button>
+        <button id="close-dialog" class="icon-button" type="button" aria-label="关闭">X</button>
+      </div>
    </div>
    <div class="sentence-scroll">
      <table>
@@ -134,6 +137,6 @@
    </div>
  </dialog>

-  <script src="/static/admin.js?v=admin-retranslate-v1" defer></script>
+  <script src="/static/admin.js?v=admin-repair-gaps-v1" defer></script>
 </body>
 </html>
--- a/sentence_api/static/admin.js
+++ b/sentence_api/static/admin.js
@@ -1,8 +1,11 @@
+const GAP_REPAIR_MIN_MS = 8000;
+
 const state = {
  adminKey: localStorage.getItem("oralTrainerAdminKey") || "",
  videos: [],
  users: [],
  retranslateVideo: null,
+  sentenceVideo: null,
 };

 const elements = {
@@ -23,6 +26,7 @@ const elements = {
  sentenceMeta: document.querySelector("#sentence-meta"),
  sentenceRows: document.querySelector("#sentence-rows"),
  closeDialog: document.querySelector("#close-dialog"),
+  repairGaps: document.querySelector("#repair-gaps"),
  retranslateDialog: document.querySelector("#retranslate-dialog"),
  retranslateTitle: document.querySelector("#retranslate-title"),
  retranslateMeta: document.querySelector("#retranslate-meta"),
@@ -45,6 +49,9 @@ elements.refresh.addEventListener("click", () => {
  loadUsers();
 });
 elements.closeDialog.addEventListener("click", () => elements.dialog.close());
+elements.repairGaps.addEventListener("click", () => {
+  if (state.sentenceVideo) repairGaps(state.sentenceVideo, { reloadSentences: true });
+});
 elements.closeRetranslateDialog.addEventListener("click", () => elements.retranslateDialog.close());
 elements.retranslateForm.addEventListener("submit", submitRetranslate);
 elements.uploadForm.addEventListener("submit", uploadVideo);
@@ -192,6 +199,7 @@ function actionCell(video) {
  actions.append(play);
  actions.append(button("改标题", () => renameVideo(video)));
  actions.append(button("句子", () => openSentences(video)));
+  actions.append(button("修复空白", () => repairGaps(video)));
  actions.append(button("重新翻译", () => openRetranslate(video)));
  actions.append(button("重新处理", () => reprocess(video.video_hash)));
  const remove = button("删除", () => deleteVideo(video));
@@ -282,19 +290,61 @@ function readXhrError(request) {
 async function openSentences(video) {
  try {
    const detail = await api(`/api/v1/videos/${video.video_hash}`);
+    state.sentenceVideo = video;
    elements.sentenceTitle.textContent = detail.video.title;
    const sentences = detail.boundaries?.sentences || [];
-    elements.sentenceMeta.textContent = `${sentences.length} 句 / ${detail.video.video_hash}`;
+    const durationMs = detail.video.duration_ms || 0;
+    const gaps = collectSentenceGaps(sentences, durationMs);
+    const gapLabel = gaps.length ? ` / ${gaps.length} 段空白待修复` : "";
+    elements.sentenceMeta.textContent = `${sentences.length} 句${gapLabel} / ${detail.video.video_hash}`;
+    elements.repairGaps.disabled = gaps.length === 0;
    elements.sentenceRows.replaceChildren();
+    let gapIndex = 0;
    for (const sentence of sentences) {
+      if (gapIndex < gaps.length && gaps[gapIndex].end_ms === sentence.start_ms) {
+        elements.sentenceRows.append(gapRow(gaps[gapIndex]));
+        gapIndex += 1;
+      }
      elements.sentenceRows.append(sentenceRow(video, sentence, sentences.length));
    }
+    if (gapIndex < gaps.length) {
+      elements.sentenceRows.append(gapRow(gaps[gapIndex]));
+    }
    if (!elements.dialog.open) elements.dialog.showModal();
  } catch (error) {
    elements.serviceState.textContent = `句子加载失败: ${error.message}`;
  }
 }

+function collectSentenceGaps(sentences, durationMs, minGapMs = GAP_REPAIR_MIN_MS) {
+  const gaps = [];
+  let cursor = 0;
+  for (const sentence of sentences) {
+    if (sentence.start_ms - cursor >= minGapMs) {
+      gaps.push({ start_ms: cursor, end_ms: sentence.start_ms });
+    }
+    cursor = Math.max(cursor, sentence.end_ms);
+  }
+  const endMs = durationMs || cursor;
+  if (endMs - cursor >= minGapMs) {
+    gaps.push({ start_ms: cursor, end_ms: endMs });
+  }
+  return gaps;
+}
+
+function gapRow(gap) {
+  const row = document.createElement("tr");
+  row.className = "gap-row";
+  row.append(
+    textCell(""),
+    textCell(`${formatDuration(gap.start_ms)} — ${formatDuration(gap.end_ms)}`),
+    textCell(`未识别空白 ${formatDuration(gap.end_ms - gap.start_ms)}`),
+    textCell(""),
+    textCell(""),
+  );
+  return row;
+}
+
 function sentenceRow(video, sentence, totalCount) {
  const row = document.createElement("tr");
  const textArea = document.createElement("textarea");
@@ -499,6 +549,36 @@ async function reprocess(videoHash) {
  }
 }

+async function repairGaps(video, options = {}) {
+  const confirmed = window.confirm(
+    `将对“${video.title}”中间隔超过 8 秒的空白重新识别。现有句子会保留，可能需要几分钟。继续？`,
+  );
+  if (!confirmed) return;
+  const button = elements.repairGaps;
+  if (button) button.disabled = true;
+  elements.serviceState.textContent = "正在重新识别空白段…";
+  try {
+    const payload = await api(`/api/v1/admin/videos/${video.video_hash}/repair-gaps`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ min_gap_ms: GAP_REPAIR_MIN_MS }),
+    });
+    if (payload.inserted_count) {
+      elements.serviceState.textContent = `空白修复完成：补了 ${payload.inserted_count} 句（${payload.transcribed_gaps}/${payload.gap_count} 段）`;
+    } else if (payload.gap_count) {
+      elements.serviceState.textContent = `发现 ${payload.gap_count} 段空白，但没有识别到新句子`;
+    } else {
+      elements.serviceState.textContent = "没有发现需要修复的空白段";
+    }
+    await loadVideos();
+    if (options.reloadSentences) await openSentences(video);
+  } catch (error) {
+    elements.serviceState.textContent = `空白修复失败: ${error.message}`;
+  } finally {
+    if (button && !options.reloadSentences) button.disabled = false;
+  }
+}
+
 async function deleteVideo(video) {
  if (!window.confirm(`删除“${video.title}”？`)) return;
  try {
--- a/sentence_api/tests/test_api.py
+++ b/sentence_api/tests/test_api.py
@@ -1029,3 +1029,139 @@ def test_admin_can_update_course_title(tmp_path):
        json={"title": "Missing course"},
    )
    assert missing_response.status_code == 404
+
+
+
+def test_admin_can_repair_sentence_gaps(tmp_path, monkeypatch):
+    settings = replace(Settings.from_env(), data_dir=tmp_path / "data")
+    settings.ensure_directories()
+    repository = VideoRepository(settings.database_path)
+    repository.upsert_upload(
+        video_hash=VIDEO_HASH,
+        title="Repair gaps lesson",
+        filename="lesson.mp4",
+        stored_filename=f"{VIDEO_HASH}.mp4",
+        content_type="video/mp4",
+        size_bytes=5,
+        language="en",
+    )
+    (settings.videos_dir / f"{VIDEO_HASH}.mp4").write_bytes(b"fake-video")
+    repository.save_processing_result(
+        SentenceBoundaryDocument(
+            video_hash=VIDEO_HASH,
+            duration_ms=18000,
+            algorithm_version="test",
+            sentences=[
+                SentenceBoundary(
+                    index=0,
+                    start_ms=0,
+                    end_ms=2000,
+                    text="Hello.",
+                    language="en",
+                    reference_speech_duration_ms=1800,
+                ),
+                SentenceBoundary(
+                    index=1,
+                    start_ms=15000,
+                    end_ms=18000,
+                    text="Goodbye.",
+                    language="en",
+                    reference_speech_duration_ms=2500,
+                ),
+            ],
+        ),
+        "Hello. Goodbye.",
+    )
+    repository.save_sentence_translations(VIDEO_HASH, {0: "你好。", 1: "再见。"})
+
+    from sentence_api.transcription import Transcript, TranscriptionSegment, _wav_bytes
+    import numpy as np
+
+    class GapTranscriber:
+        available = True
+
+        def transcribe(self, audio_path, language=None):
+            return Transcript(
+                text="The missing sentence.",
+                segments=[
+                    TranscriptionSegment(
+                        start_seconds=1.0,
+                        end_seconds=5.0,
+                        text="The missing sentence.",
+                    )
+                ],
+            )
+
+    def fake_extract(media_path, output_path, *, start_ms, duration_ms):
+        sample_rate = 16000
+        t = np.arange(int(max(1.0, duration_ms / 1000) * sample_rate)) / sample_rate
+        samples = (0.25 * np.sin(2 * np.pi * 220 * t)).astype(np.float32)
+        output_path.write_bytes(_wav_bytes(samples, sample_rate))
+
+    monkeypatch.setattr("sentence_api.processing.extract_audio_segment", fake_extract)
+    client = TestClient(
+        create_app(
+            BoundaryStore(tmp_path / "boundaries.json"),
+            settings=settings,
+            repository=repository,
+            transcriber=GapTranscriber(),
+        )
+    )
+
+    response = client.post(f"/api/v1/admin/videos/{VIDEO_HASH}/repair-gaps")
+
+    assert response.status_code == 200, response.text
+    payload = response.json()
+    assert payload["gap_count"] == 1
+    assert payload["inserted_count"] == 1
+    assert payload["sentence_count"] == 3
+    document = repository.get_document(VIDEO_HASH)
+    assert [item.text for item in document.sentences] == [
+        "Hello.",
+        "The missing sentence.",
+        "Goodbye.",
+    ]
+    assert [item.zh_text for item in document.sentences] == ["你好。", None, "再见。"]
+
+
+def test_admin_gap_repair_requires_transcriber(tmp_path):
+    settings = replace(Settings.from_env(), data_dir=tmp_path / "data")
+    settings.ensure_directories()
+    repository = VideoRepository(settings.database_path)
+    repository.upsert_upload(
+        video_hash=VIDEO_HASH,
+        title="Repair gaps lesson",
+        filename="lesson.mp4",
+        stored_filename=f"{VIDEO_HASH}.mp4",
+        content_type="video/mp4",
+        size_bytes=5,
+        language="en",
+    )
+    (settings.videos_dir / f"{VIDEO_HASH}.mp4").write_bytes(b"fake-video")
+    repository.save_processing_result(
+        SentenceBoundaryDocument(
+            video_hash=VIDEO_HASH,
+            duration_ms=18000,
+            algorithm_version="test",
+            sentences=[
+                SentenceBoundary(index=0, start_ms=0, end_ms=2000, text="Hello."),
+                SentenceBoundary(index=1, start_ms=15000, end_ms=18000, text="Goodbye."),
+            ],
+        ),
+        None,
+    )
+
+    class UnavailableTranscriber:
+        available = False
+
+    client = TestClient(
+        create_app(
+            BoundaryStore(tmp_path / "boundaries.json"),
+            settings=settings,
+            repository=repository,
+            transcriber=UnavailableTranscriber(),
+        )
+    )
+
+    response = client.post(f"/api/v1/admin/videos/{VIDEO_HASH}/repair-gaps")
+    assert response.status_code == 503
--- a/sentence_api/tests/test_processing.py
+++ b/sentence_api/tests/test_processing.py
@@ -4,6 +4,7 @@ from sentence_api.processing import (
    MOSS_ALGORITHM_VERSION,
    VideoProcessor,
    document_from_transcript,
+    find_sentence_gaps,
    split_sentence_text,
 )
 from sentence_api.models import SentenceBoundary, SentenceBoundaryDocument
@@ -381,3 +382,178 @@ def test_mark_processing_clears_previous_sentence_data(tmp_path):
    assert document.sentences == []
    assert repository.get_moss_segments(VIDEO_HASH) == []

+
+
+
+def test_find_sentence_gaps_detects_leading_middle_and_trailing():
+    document = SentenceBoundaryDocument(
+        video_hash=VIDEO_HASH,
+        duration_ms=60000,
+        algorithm_version="test",
+        sentences=[
+            SentenceBoundary(index=0, start_ms=10000, end_ms=12000, text="A"),
+            SentenceBoundary(index=1, start_ms=25000, end_ms=27000, text="B"),
+        ],
+    )
+
+    assert find_sentence_gaps(document, min_gap_ms=8000) == [
+        (0, 10000),
+        (12000, 25000),
+        (27000, 60000),
+    ]
+
+
+def test_find_sentence_gaps_ignores_short_pauses():
+    document = SentenceBoundaryDocument(
+        video_hash=VIDEO_HASH,
+        duration_ms=9000,
+        algorithm_version="test",
+        sentences=[
+            SentenceBoundary(index=0, start_ms=0, end_ms=4000, text="A"),
+            SentenceBoundary(index=1, start_ms=4500, end_ms=9000, text="B"),
+        ],
+    )
+
+    assert find_sentence_gaps(document) == []
+
+
+def test_repair_gaps_inserts_transcribed_sentences_and_keeps_existing(tmp_path, monkeypatch):
+    from dataclasses import replace
+
+    from sentence_api.config import Settings
+
+    settings = replace(Settings.from_env(), data_dir=tmp_path / "data")
+    settings.ensure_directories()
+    repository = VideoRepository(settings.database_path)
+    repository.upsert_upload(
+        video_hash=VIDEO_HASH,
+        title="Gap repair lesson",
+        filename="lesson.mp4",
+        stored_filename=f"{VIDEO_HASH}.mp4",
+        content_type="video/mp4",
+        size_bytes=5,
+        language="en",
+    )
+    (settings.videos_dir / f"{VIDEO_HASH}.mp4").write_bytes(b"fake-video")
+    repository.save_processing_result(
+        SentenceBoundaryDocument(
+            video_hash=VIDEO_HASH,
+            duration_ms=18000,
+            algorithm_version="test",
+            sentences=[
+                SentenceBoundary(
+                    index=0,
+                    start_ms=0,
+                    end_ms=2000,
+                    text="Hello.",
+                    language="en",
+                    reference_speech_duration_ms=1800,
+                ),
+                SentenceBoundary(
+                    index=1,
+                    start_ms=15000,
+                    end_ms=18000,
+                    text="Goodbye.",
+                    language="en",
+                    reference_speech_duration_ms=2500,
+                ),
+            ],
+        ),
+        "Hello. Goodbye.",
+    )
+    repository.save_sentence_translations(VIDEO_HASH, {0: "你好。", 1: "再见。"})
+
+    class GapTranscriber:
+        available = True
+        calls = 0
+
+        def transcribe(self, audio_path, language=None):
+            self.calls += 1
+            return Transcript(
+                text="The missing sentence.",
+                segments=[
+                    TranscriptionSegment(
+                        start_seconds=1.0,
+                        end_seconds=5.0,
+                        text="The missing sentence.",
+                    )
+                ],
+            )
+
+    def fake_extract(media_path, output_path, *, start_ms, duration_ms):
+        output_path.write_bytes(_wav_bytes(_speech(max(1.0, duration_ms / 1000)), SAMPLE_RATE))
+
+    monkeypatch.setattr("sentence_api.processing.extract_audio_segment", fake_extract)
+    transcriber = GapTranscriber()
+    result = VideoProcessor(settings, repository, transcriber).repair_gaps(VIDEO_HASH)
+
+    assert result["gap_count"] == 1
+    assert result["transcribed_gaps"] == 1
+    assert result["inserted_count"] == 1
+    assert transcriber.calls == 1
+    document = repository.get_document(VIDEO_HASH)
+    assert [sentence.text for sentence in document.sentences] == [
+        "Hello.",
+        "The missing sentence.",
+        "Goodbye.",
+    ]
+    assert document.sentences[0].zh_text == "你好。"
+    assert document.sentences[1].zh_text is None
+    assert document.sentences[2].zh_text == "再见。"
+    assert document.sentences[0].end_ms <= document.sentences[1].start_ms
+    assert document.sentences[1].end_ms <= document.sentences[2].start_ms
+    assert document.sentences[1].start_ms >= 2000
+    assert document.sentences[1].end_ms <= 15000
+
+
+def test_repair_gaps_skips_silent_gaps(tmp_path, monkeypatch):
+    from dataclasses import replace
+
+    from sentence_api.config import Settings
+
+    settings = replace(Settings.from_env(), data_dir=tmp_path / "data")
+    settings.ensure_directories()
+    repository = VideoRepository(settings.database_path)
+    repository.upsert_upload(
+        video_hash=VIDEO_HASH,
+        title="Silent gap lesson",
+        filename="lesson.mp4",
+        stored_filename=f"{VIDEO_HASH}.mp4",
+        content_type="video/mp4",
+        size_bytes=5,
+        language="en",
+    )
+    (settings.videos_dir / f"{VIDEO_HASH}.mp4").write_bytes(b"fake-video")
+    repository.save_processing_result(
+        SentenceBoundaryDocument(
+            video_hash=VIDEO_HASH,
+            duration_ms=18000,
+            algorithm_version="test",
+            sentences=[
+                SentenceBoundary(index=0, start_ms=0, end_ms=2000, text="Hello."),
+                SentenceBoundary(index=1, start_ms=15000, end_ms=18000, text="Goodbye."),
+            ],
+        ),
+        None,
+    )
+
+    class TrackingTranscriber:
+        available = True
+        calls = 0
+
+        def transcribe(self, audio_path, language=None):
+            self.calls += 1
+            return Transcript(text="hallucinated", segments=[])
+
+    def fake_extract(media_path, output_path, *, start_ms, duration_ms):
+        output_path.write_bytes(_wav_bytes(_silence(max(1.0, duration_ms / 1000)), SAMPLE_RATE))
+
+    monkeypatch.setattr("sentence_api.processing.extract_audio_segment", fake_extract)
+    transcriber = TrackingTranscriber()
+    result = VideoProcessor(settings, repository, transcriber).repair_gaps(VIDEO_HASH)
+
+    assert result["gap_count"] == 1
+    assert result["inserted_count"] == 0
+    assert transcriber.calls == 0
+    document = repository.get_document(VIDEO_HASH)
+    assert [sentence.text for sentence in document.sentences] == ["Hello.", "Goodbye."]
--- a/sentence_api/translation_jobs.py
+++ b/sentence_api/translation_jobs.py
@@ -116,6 +116,23 @@ class SubtitleTranslationService:
        except (KeyError, ValueError, AITutorError):
            logger.exception("Could not restart subtitle translation: video=%s", video_hash)

+    def start_missing(self, video_hash: str) -> None:
+        """Translate sentences that still lack Chinese text, keeping existing ones."""
+        if not getattr(self.ai_tutor, "available", False):
+            return
+        document = self.repository.get_document(video_hash)
+        if document is None:
+            return
+        if self.snapshot(document).complete:
+            return
+        try:
+            self._start_if_needed(video_hash)
+        except (KeyError, ValueError, AITutorError):
+            logger.exception(
+                "Could not start subtitle translation after gap repair: video=%s",
+                video_hash,
+            )
+
    def admin_snapshot(self, video_hash: str) -> AdminSubtitleTranslationResponse | None:
        current = self.current(video_hash)
        if current is None: