type VideoBitrateMode = "System" | "Auto";Selects how the video bitrate is determined when no explicit bitrate is given.
'System': let the platform encoder choose the bitrate (the default). In the browser this can be a very high, near-lossless rate that may cause large exports to fail with an out-of-memory error.'Auto': a bounded default derived from the output resolution and framerate, consistent across platforms.