1e6f21c34d
Regression is caused by movie being rendered twice for the same frame
number, but the image is not cached after 5ecb70964e.
The image is rendered first to determine `early_out` in
`seq_render_strip_stack()`, then for the actual image output.
Since VSE cache is not to be used for render job, `ffmpeg_fetchibuf()`
can be optimized to return frame, which is already decoded instead of
re-seeking to last keyframe and decoding all following frames again.
Pull Request: https://projects.blender.org/blender/blender/pulls/126911