fix: 修复 _has_audio() 始终返回 True 的 P0 问题

- 仅当 clip_type 不是 title/subtitle 时才设置 audio_label
- title/subtitle 是纯文字/图片卡片，没有音频流
- 添加 7 个单元测试验证修复逻辑
- 所有 36 个测试通过

apps/api/app/services/video_compose_service.py

@@ -428,12 +428,11 @@ class VideoComposeService:
 
         video_label = f"v{input_index}"
 
-        # 5. atrim: 音频时长（假设输入可能有音频）
-        audio_filters = [
-            f"atrim=0:{duration}",
-            "asetpts=PTS-STARTPTS",
-        ]
-        audio_label = f"a{input_index}"
+        # 5. 音频标签：仅当片段类型可能有音频时才设置
+        # title/subtitle 是纯文字/图片卡片，没有音频流
+        clip_type = clip.clip_type.lower() if clip.clip_type else ""
+        has_audio_stream = clip_type not in ("title", "subtitle")
+        audio_label = f"a{input_index}" if has_audio_stream else None
 
         return ClipFilterChain(
             clip_id=clip.id,

tests/unit/test_video_compose_service.py

@@ -560,6 +560,68 @@ class TestBuildXfadeFilter(TestCase):
         self.assertAlmostEqual(duration, 14.0, places=2)
 
 
+class TestHasAudioTitleSubtitleFix(TestCase):
+    """P0 修复验证：title/subtitle 片段不应有音频流。"""
+
+    def _make_clip(self, clip_id, clip_type, **kwargs):
+        """创建测试用 stub clip。"""
+        return _StubClip(clip_id=clip_id, clip_type=clip_type, **kwargs)
+
+    def test_title_clip_has_no_audio_label(self):
+        """title 类型片段的 audio_label 应为 None。"""
+        clip = self._make_clip("c1", "title")
+        chain = VideoComposeService._build_clip_filter(clip, 0, 1280, 720, 25)
+        self.assertIsNone(chain.audio_label, "title 片段不应有音频标签")
+
+    def test_subtitle_clip_has_no_audio_label(self):
+        """subtitle 类型片段的 audio_label 应为 None。"""
+        clip = self._make_clip("c1", "subtitle")
+        chain = VideoComposeService._build_clip_filter(clip, 0, 1280, 720, 25)
+        self.assertIsNone(chain.audio_label, "subtitle 片段不应有音频标签")
+
+    def test_main_clip_has_audio_label(self):
+        """main 类型片段应有音频标签。"""
+        clip = self._make_clip("c1", "main")
+        chain = VideoComposeService._build_clip_filter(clip, 0, 1280, 720, 25)
+        self.assertEqual(chain.audio_label, "a0")
+
+    def test_intro_clip_has_audio_label(self):
+        """intro 类型片段应有音频标签。"""
+        clip = self._make_clip("c1", "intro")
+        chain = VideoComposeService._build_clip_filter(clip, 0, 1280, 720, 25)
+        self.assertEqual(chain.audio_label, "a0")
+
+    def test_has_audio_false_when_only_title_subtitle(self):
+        """当所有片段都是 title/subtitle 时，_has_audio 应返回 False。"""
+        chains = [
+            VideoComposeService._build_clip_filter(
+                self._make_clip("c1", "title"), 0, 1280, 720, 25
+            ),
+            VideoComposeService._build_clip_filter(
+                self._make_clip("c2", "subtitle"), 1, 1280, 720, 25
+            ),
+        ]
+        self.assertFalse(VideoComposeService._has_audio(chains))
+
+    def test_has_audio_true_when_mixed_clips(self):
+        """混合片段（含 main）时，_has_audio 应返回 True。"""
+        chains = [
+            VideoComposeService._build_clip_filter(
+                self._make_clip("c1", "title"), 0, 1280, 720, 25
+            ),
+            VideoComposeService._build_clip_filter(
+                self._make_clip("c2", "main"), 1, 1280, 720, 25
+            ),
+        ]
+        self.assertTrue(VideoComposeService._has_audio(chains))
+
+    def test_empty_clip_type_has_audio(self):
+        """clip_type 为空字符串时，应有音频标签（保守策略）。"""
+        clip = self._make_clip("c1", "")
+        chain = VideoComposeService._build_clip_filter(clip, 0, 1280, 720, 25)
+        self.assertEqual(chain.audio_label, "a0")
+
+
 if __name__ == "__main__":
     import unittest
     unittest.main()