Fix audio stretching of DTS on BD rips (and down mix to stereo):

DTS and DTS master audio is lossless audio quality, but has stretching sounds when repeating a certain section + missing interments.
As well as most Blu-Ray movies missing a stereo option for sound. While most are meant for directors comments or describe video. plus audio is not as good quality.
Lucky, FFmpeg on Linux can fix it by using the Flac audio codic instead of a proprietary one, so it is still lossless. plus I can down mix to stereo from surround in the process. As well not touch the video codec

Command: ffmpeg -i old.mkv -acodec flac -compression_level 8 -ac 2 -vcodec copy new.mkv

The "-ac 2" flag means down mix to two channels (stereo).
The "

-vcodec copy" flag means move video coec to new file without any editing of it. 

The "-acodec flac" flag means convert to the Flac codec. 

old.mkv is old file and new.mkv is your new file. They must be a different name or else it will overwrite, plus the old file is till open to possible data corruption.





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

https://branden-g.ca/Notes/Tech-Help/Linux-Repair/ffmpeg/Pass-through-Blu-ray-video-from-MKV-to-MP4-with-ffmpeg.php

https://stackoverflow.com/questions/44836653/ffmpegs-flac-compression-levels-defaults-settings

https://z-issue.com/wp/flac-compression-level-comparison/


Date: May 13th, 2021













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