Meta wants a fixed frame rate: set Timeline output.fps when clips mix

Meta's Facebook feed video page lists H.264 compression, square pixels, a fixed frame rate, progressive scan and stereo AAC audio at 128kbps or more. In a Sume Timeline render, set output.fps to 24, 25, 30 or 60 when your clips have different frame rates, so the whole video has one rate that you chose.

What Timeline does with frame rate

The Timeline docs say output.fps is one of 24, 25, 30 or 60. If you omit it, the job renders at the rate of the sources: the longest video sources decide, stills have no rate, and 30 applies only when no source has one. If the output rate differs from a source's rate, the job repeats or drops a frame every few frames, which causes judder on motion, and the result reports output_fps_resamples_sources with the rate the sources wanted.

Pick the rate of the most motion

Since resampling is what causes judder, set output.fps to the rate of the clip with the fastest motion. A talking head cut at 24 loses little when a 30 fps clip is dropped to 24; a fast pan shot at 60 does. Check the response's warnings after the first render.

What Sume does not state

The docs describe a single output rate, but they do not say the stream is flagged constant frame rate, and they do not list the codec, square pixels, progressive scan or AAC bitrate. Treat those Meta requirements as things to check on the file you download. The Facebook page also says videos should not include edit lists, which the Timeline docs do not address either.

A final check after the render: read the job result's warnings. If output_fps_resamples_sources appears, you saw exactly the conflict described above, and you can decide whether the judder matters for the shot. For a mostly static product clip it rarely does; for a pan or a hand-held walk it can. Re-render with the other rate if the motion looks uneven.