trying to fix export issue and waveform load

backend/services/video_editor.py

@@ -13,6 +13,24 @@ from typing import List
 logger = logging.getLogger(__name__)
 
 
+def _input_has_video_stream(ffmpeg_cmd: str, input_path: str) -> bool:
+    """Return True if the input contains at least one video stream."""
+    ffprobe = ffmpeg_cmd.replace("ffmpeg", "ffprobe")
+    cmd = [
+        ffprobe,
+        "-v", "error",
+        "-select_streams", "v:0",
+        "-show_entries", "stream=index",
+        "-of", "csv=p=0",
+        str(input_path),
+    ]
+    try:
+        result = subprocess.run(cmd, capture_output=True, text=True)
+        return result.returncode == 0 and bool(result.stdout.strip())
+    except Exception:
+        return False
+
+
 def _clamp_speed(speed: float) -> float:
     return max(0.25, min(4.0, float(speed)))
 
@@ -120,6 +138,10 @@ def export_stream_copy(
         # Mute ranges require audio filtering, so fall back to re-encoding
         return export_reencode(input_path, output_path, keep_segments, "1080p", "mp4", mute_ranges)
     ffmpeg = _find_ffmpeg()
+    if not _input_has_video_stream(ffmpeg, input_path):
+        # Audio-only inputs cannot use TS segment stream-copy concat reliably.
+        return export_reencode(input_path, output_path, keep_segments)
+
     input_path = str(Path(input_path).resolve())
     output_path = str(Path(output_path).resolve())
 
@@ -222,10 +244,66 @@ def export_reencode(
         return ",".join(filters) if filters else "anull"
 
     has_audio_filters = bool(mute_ranges) or bool(gain_ranges) or abs(float(global_gain_db)) > 1e-6
+    has_video = _input_has_video_stream(ffmpeg, input_path)
 
     speed_segments = _split_keep_segments_by_speed(keep_segments, speed_ranges)
     has_speed = any(abs(seg.get("speed", 1.0) - 1.0) > 1e-6 for seg in speed_segments)
 
+    if not has_video:
+        if not keep_segments:
+            raise ValueError("No segments to export")
+
+        segments_for_concat = speed_segments if speed_segments else _split_keep_segments_by_speed(keep_segments, None)
+        if not segments_for_concat:
+            raise ValueError("No segments to export")
+
+        filter_parts = []
+        for i, seg in enumerate(segments_for_concat):
+            speed = _clamp_speed(seg.get("speed", 1.0))
+            a_chain = f"atrim=start={seg['start']}:end={seg['end']},asetpts=PTS-STARTPTS"
+            if abs(speed - 1.0) > 1e-6:
+                a_chain += f",{_build_atempo_chain(speed)}"
+            filter_parts.append(f"[0:a]{a_chain}[a{i}];")
+
+        n = len(segments_for_concat)
+        concat_inputs = "".join(f"[a{i}]" for i in range(n))
+        filter_parts.append(f"{concat_inputs}concat=n={n}:v=0:a=1[outa_raw]")
+
+        audio_filter = build_audio_filter()
+        if audio_filter != "anull":
+            filter_parts.append(f";[outa_raw]{audio_filter}[outa]")
+            audio_map = "[outa]"
+        else:
+            audio_map = "[outa_raw]"
+
+        filter_complex = "".join(filter_parts)
+
+        audio_codec_args = ["-c:a", "aac", "-b:a", "192k"]
+        if format_hint == "webm":
+            audio_codec_args = ["-c:a", "libopus", "-b:a", "160k"]
+
+        cmd = [
+            ffmpeg, "-y",
+            "-i", input_path,
+            "-filter_complex", filter_complex,
+            "-map", audio_map,
+            *audio_codec_args,
+            output_path,
+        ]
+
+        logger.info(
+            "Re-encoding audio-only input (%s segments, speed-adjusted=%s) -> %s",
+            n,
+            has_speed,
+            output_path,
+        )
+
+        result = subprocess.run(cmd, capture_output=True, text=True)
+        if result.returncode != 0:
+            raise RuntimeError(f"FFmpeg audio-only export failed: {result.stderr[-500:]}")
+
+        return output_path
+
     # Handle filtered full-timeline audio case (mute/gain/global gain) when no speed warping is needed
     if has_audio_filters and not has_speed:
         audio_filter = build_audio_filter()
@@ -344,6 +422,9 @@ def export_reencode_with_subs(
     If mute_ranges are provided, applies audio muting instead of cutting.
     """
     ffmpeg = _find_ffmpeg()
+    if not _input_has_video_stream(ffmpeg, input_path):
+        raise ValueError("Burn-in captions require a video track")
+
     input_path = str(Path(input_path).resolve())
     output_path = str(Path(output_path).resolve())
     subtitle_path = str(Path(subtitle_path).resolve())