Fix audio strecthing of DTS on BD rips (and downmix to sterio):
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DTS and DTS master audio is lossless audio quality, but has stretching sounds when repeating a certain section + missing interments.
As well as most blueray movies missing a sterio option for sound (most are ment for directors comments or describe video. plus audio is not as good quality.
Luckly, ffmpeg on Linux can fix it by using the flac audio codic instad of a priparity one, so it is still lossless. plus I can downmix to sterio from suround in the process.
(And mot touch video codec).
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Command:
ffmpeg -i old.mkv -acodec flac -compression_level 8 -ac 2 -vcodec copy new.mkv

The "-ac 2" flag means downmix to two chanels (sterio). "-vcodec copy" means move video coec to new file without any editing of it. "-acodec flac" means convert to the flac codec. old.mkv is old file and new.mkv is your new file (must be a diffrent name or else it will overwrite, plus the old file is till open so possable data coruption).


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Sources:
https://superuser.com/questions/339023/convert-audio-file-to-flac-with-ffmpeg
https://superuser.com/questions/852400/properly-downmix-5-1-to-stereo-using-ffmpeg
https://en.wikipedia.org/wiki/Comparison_of_video_container_formats
http://99.248.197.130/Notes/Tech%20Help/Linux%20Repair/ffmpeg/Pass%20through%20Blu-ray%20video%20from%20MKV%20to%20MP4%20with%20ffmpeg.txt
https://stackoverflow.com/questions/44836653/ffmpegs-flac-compression-levels-defaults-settings
https://z-issue.com/wp/flac-compression-level-comparison/

Date: May 13th, 2021