After threaded architecture change, conversion of inputs with DVD subtitles yields incorrect duration and progress is strange

[Marth64]

Summary of the bug:

After threaded architecture change, conversion of inputs with DVD subtitles yields incorrect duration and progress is strange. For longer files, ffmpeg will see time as N/A for couple seconds, while bitrate grows unrealistically high. In all cases, output duration is printed wrong.

Discovered this while working on DVD demuxer, but issue is independent of the demuxer entirely.

Can be reproduced with sample file already available: ​https://samples.ffmpeg.org/MPEG-VOB/inverse_telecine_problem/vts_01_1.1st_50M.vob

Issue is not reproducible prior to this change.

How to reproduce:

ffmpeg -probesize 512M -analyzeduration 60000000 -fflags +genpts -i vts_01_1.1st_50M.vob -map 0:v -map 0:a -map 0:s -c copy -f matroska Parallelissue.mkv

Prints: time=00:00:47.81

Aactual time, and time shown prior to threaded arch change: time=00:01:32.65