estimated-frame-number off-by-one and incorrect display when reversing frame direction.

Important Information

• mpv 0.33.0-336-g62b2c5db98
• Windows 11 (OS Build 22454.1000)
• shinchiro sourceforge 64bit builds

Reproduction steps

input.conf

CTRL+RIGHT  frame-step ; show-text "Frame: ${estimated-frame-number} / ${estimated-frame-count}"
CTRL+LEFT   frame-back-step ; show-text "Frame: ${estimated-frame-number} / ${estimated-frame-count}"

• Frame-step twice.
• Frame-back-step once.
• Experience wrong frame count on OSD.

Expected behavior

Accurate frame count display on OSD when transitioning frames one at a time in any direction.

Actual behavior

When you open a video file and start at 0:00, advancing one frame with frame-step shows the frame count as 0 on the OSD. Likewise, if you advance frames and decide to reverse directions, the frame display continues to count in the opposite direction for the first frame.

frame-step > frame-step > frame-step > frame-back-step > frame-back-step
Displays as;
0, 1, 2, 3, 2

When starting at absolute 0:00, if you consider the first frame to be 0, it should display as;
1, 2, 3, 2, 1

Otherwise if you consider the first frame in the video to actually be the first frame, it should display as;
2, 3, 4, 3, 2

If you are back-stepping frames and decide to forward a frame, the OSD will keep counting backwards until the 2nd consecutive forward.

Log file

output.txt

Sample files

Reproducible with any mkv video file, no sample needed.

Start by reproducing the behavior with the input.conf bindings and a video file, then review output.txt alongside the estimated-frame-number and estimated-frame-count behavior. Verify frame-step and frame-back-step when changing direction, and consider the issue done when the OSD reports the expected sequence consistently in both directions.