Removing infinite buffering length for a background video

gnommo/cli.py

@@ -2802,7 +2802,10 @@ def cmd_preprocess(
         entry = dict(existing_narration.get(segment_id, {}))
         # Always record the plain path; the res subdir shift happens at render for low/tiny.
         entry["processed_file"] = f"processed/{segment_id}_processed.mov"
-        entry.setdefault("use_audio_channels", "auto")
+        # Store the RESOLVED audio channel (preprocess_video mutated "auto" → the
+        # detected left/right/both). This is the concrete value; render reads it and
+        # never re-runs the auto-detect probe.
+        entry["use_audio_channels"] = segment_source.use_audio_channels or "auto"
         entry.setdefault("defer_loudnorm", False)
         existing_narration[segment_id] = entry
 

gnommo/preprocessor.py

@@ -715,6 +715,10 @@ def preprocess_video(
     if channel == "auto":
         channel = _resolve_auto_channel(current_input)
         print(f"        Auto channel detection: using '{channel}'")
+        # Persist the resolved channel on the source so the caller can store it back
+        # to narration.json — the auto-detect (a full-file volumedetect) then runs
+        # ONCE here at preprocess, never again at render time.
+        video_source.use_audio_channels = channel
     elif channel in ("left", "right"):
         is_silent, max_vol = check_audio_channel_silent(current_input, channel)
         if is_silent:

gnommo/renderer.py

@@ -319,12 +319,15 @@ def _build_audio_channel_filter(use_audio_channels: str) -> str:
         use_audio_channels: "both", "left", or "right"
 
     Returns:
-        Filter string (e.g., "pan=mono|c0=c1") or empty string for "both"
+        Filter string, or empty string for "both".
+
+    Matches preprocess (apply_audio_normalize): a selected single channel is
+    duplicated to BOTH output channels (centered stereo), not collapsed to mono.
     """
     if use_audio_channels == "left":
-        return "pan=mono|c0=c0"
+        return "pan=stereo|c0=c0|c1=c0"
     elif use_audio_channels == "right":
-        return "pan=mono|c0=c1"
+        return "pan=stereo|c0=c1|c1=c1"
     return ""  # "both" - no filter needed
 
 
@@ -458,9 +461,13 @@ def build_ffmpeg_command(plan: RenderPlan, output_path: Path) -> list[str]:
             )
         image_extensions = {".png", ".jpg", ".jpeg", ".gif", ".bmp", ".tiff", ".webp"}
         bg_is_image = bg_path.suffix.lower() in image_extensions
-        # Loop background videos infinitely
+        # Loop background videos, but BOUND the loop to the output length. An
+        # unbounded -stream_loop -1 input can make ffmpeg read/buffer ahead without
+        # limit, which balloons memory on long renders — cap it with an input -t so
+        # it EOFs cleanly at total_duration.
         if not bg_is_image:
             cmd.extend(["-stream_loop", "-1"])
+            cmd.extend(["-t", f"{plan.total_duration:.3f}"])
         # Duration of background video is irrelevant (looped or image) — skip analysis
         cmd.extend(["-analyzeduration", "0", "-probesize", "1000"])
         cmd.extend(["-i", str(bg_path)])