Fix: handle no-audio video in transcode_for_browser; fallback on error

app.py

@@ -160,26 +160,32 @@ def _transcode_for_browser(video_path: str) -> str:
     """Re-encode *video_path* to H.264 baseline + AAC so all browsers can preview it.
 
     Returns the path to the transcoded file (written alongside the original).
-    If the input is already browser-safe the re-encode is still cheap (~1s for
-    short clips) and ensures consistent behaviour across all upload sources.
+    Falls back to returning the original path if transcoding fails.
     """
     if video_path is None:
         return video_path
-    out_path = video_path.rsplit(".", 1)[0] + "_browser.mp4"
-    (
-        ffmpeg
-        .input(video_path)
-        .output(
-            out_path,
+    try:
+        # Probe to check if audio stream exists
+        probe = ffmpeg.probe(video_path)
+        has_audio = any(s["codec_type"] == "audio" for s in probe.get("streams", []))
+        out_path = video_path.rsplit(".", 1)[0] + "_browser.mp4"
+        stream = ffmpeg.input(video_path)
+        output_kwargs = dict(
             vcodec="libx264", preset="fast", crf=18,
             profile="baseline", level="3.0",
             pix_fmt="yuv420p",
-            acodec="aac", audio_bitrate="128k",
             movflags="+faststart",
         )
-        .run(overwrite_output=True, quiet=True)
-    )
-    return out_path
+        if has_audio:
+            output_kwargs["acodec"] = "aac"
+            output_kwargs["audio_bitrate"] = "128k"
+        else:
+            output_kwargs["an"] = None  # no audio track
+        stream.output(out_path, **output_kwargs).run(overwrite_output=True, quiet=True)
+        return out_path
+    except Exception as e:
+        print(f"[transcode_for_browser] failed, using original: {e}")
+        return video_path
 
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