[Scummvm-tracker] [ScummVM :: Bugs] #16966: NANCY: Poor performance spinning around a room

[ScummVM :: Bugs]

#16966: NANCY: Poor performance spinning around a room
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Reporter:  tunnelsociety                         |      Owner:  (none)
    Type:  defect                                |     Status:  new
Priority:  normal                                |  Component:  Engine:
                                                 |  Nancy
 Version:                                        |   Keywords:
    Game:  Nancy Drew: Curse of Blackmoor Manor  |
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 In any room where we can spin around to see the whole room (e.g. "Gameplay
 Overview"/tutorial), turning left from a certain point is fine at first,
 but as we continue left it gradually becomes slower, like a full second or
 more between turns, until a full rotation is completed -- then it is fast
 again, and again slows as we turn.
 (Turning rightward, it is slow immediately, and gradually gets faster.)

 Recording is attached to demonstrate the slowdown, compared to Shadow
 Ranch.

 I continue to experience this when building with -O3, but it is improved
 from a second or more to somewhat less than a second. (Still very
 noticeable and somewhat frustrates gameplay: the cursor gets stuck in
 place during the interruptions, temporarily not responding to mouse
 movement after releasing the held button.

 During the slowdowns, CPU usage briefly goes to ~100%.
 I guess it has to do with [re]decoding and [re]seeking a video. I did a
 little profiling to produce the attached flame graphs. When I spin around
 in Nancy10 (Shadow Ranch) or earlier, I don't experience this, so I attach
 a graph for Shadow Ranch to compare.
 These graphs are produced from many samples of me spinning around a room
 for thirty seconds.
 (These SVG have some JavaScript and can be viewed interactively in a
 browser like Firefox: zoom in by clicking a function.)

 Blackmoor's graph's leftmost side looks like all of Shadow Ranch's. But
 the large majority of Blackmoor's graph is
 Video::VideoDecoder::seekToFrame, which we don't really see in Shadow
 Ranch's.

 ScummVM 2026.3.1git8143-g32091910a7b
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Ticket URL: <https://bugs.scummvm.org/ticket/16966>
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