VideoFromComponents crashes with 'Could not determine output format' when writing to BytesIO

[artokun]

Custom Node Testing

• I have tried disabling custom nodes and the issue persists

Your question

When a tensor-based video (from Create Video or similar nodes) is passed to any node that calls validate_container_format_is_mp4() — like TopazVideoEnhance — it crashes with ValueError: Could not determine output format.

The issue is in VideoFromComponents.save_to(). When get_container_format() calls get_stream_source(), it passes a BytesIO() buffer to save_to(). Since BytesIO has no file extension, av.open can't infer the output format.

VideoFromFile.save_to() already handles this correctly via get_open_write_kwargs(), which detects BytesIO and sets the format explicitly. VideoFromComponents just never got the same treatment.

Logs

File "comfy_api/latest/_input_impl/video_types.py", line 411, in save_to
    with av.open(path, mode='w', options={'movflags': 'use_metadata_tags'}, **extra_kwargs) as output:
ValueError: Could not determine output format

OS

Windows 11

ComfyUI Revision / Version

v0.15.1