ytdl_hook.lua parse playlist error on bilibili interactive video

mpv Information

mpv v0.39.0-927-g5338f4ba7 Copyright © 2000-2025 mpv/MPlayer/mplayer2 projects
 built on Feb 26 2025 16:05:41
libplacebo version: v7.350.0 (v7.349.0-37-g7de2415-dirty)
FFmpeg version: N-118547-ge24920375
FFmpeg library versions:
   libavcodec      61.33.102
   libavdevice     61.4.100
   libavfilter     10.9.100
   libavformat     61.9.107
   libavutil       59.57.100
   libswresample   5.4.100
   libswscale      8.13.100

Other Information

- Windows version: Win11 24H2
- GPU model, driver and version:
- Source of mpv: https://github.com/zhongfly/mpv-winbuild/releases/tag/2025-02-26-5338f4b
- Latest known working version:
- Issue started after the following happened:

Reproduction Steps

Interactive video is a special type of video in bilibili, different choices will have different results, yt-dlp outputs all branches as a playlist.
https://www.bilibili.com/video/BV1g5pqeBEXP/

• source of yt-dlp: https://github.com/yt-dlp/yt-dlp/releases/tag/2025.02.19
• run mpv "ytdl://https://www.bilibili.com/video/BV1g5pqeBEXP/"

Expected Behavior

N/A

Actual Behavior

Line 1167 site is nil
https://github.com/mpv-player/mpv/blob/5338f4ba70903e7517bbfc7881e10ff13a912ffc/player/lua/ytdl_hook.lua#L1167-L1175

Log File

yt-dlp_stdout.json

Sample Files

N/A

I carefully read all instruction and confirm that I did the following:

• I tested with the latest mpv version to validate that the issue is not already fixed.
• I provided all required information including system and mpv version.
• I produced the log file with the exact same set of files, parameters, and conditions used in "Reproduction Steps", with the addition of --log-file=output.txt.
• I produced the log file while the behaviors described in "Actual Behavior" were actively observed.
• I attached the full, untruncated log file.
• I attached the backtrace in the case of a crash.

Start with player/lua/ytdl_hook.lua around lines 1167-1175 and reproduce the issue using the bilibili URL and the provided mpv command. Compare the attached yt-dlp_stdout.json with the playlist-parsing assumptions at the failing line. Done means the interactive video no longer errors when its branches are returned as a playlist.