Will my animated WebP keep its frame timing in the MP4?
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Yes — per-frame delays in the animated WebP are read and reproduced as the MP4 frame rate, so the motion plays at the original speed. Variable frame delays are normalized to a constant rate that preserves overall timing.
Most video formats do not store an alpha channel, so a transparent WebP is composited onto a solid background (white by default, configurable) in the MP4. If you must keep transparency, a video target is the wrong format — keep it as an image.
