ffmpeg via terminal

ffmpeg

$ echo "Enter m3u8 link:";read link;echo "Enter output filename:";read filename;ffmpeg -i "$link" -bsf:a aac_adtstoasc -vcodec copy -c copy -crf 50 $filename.mp4

$ ffmpeg -i "http://host/folder/file.m3u8" -bsf:a aac_adtstoasc -vcodec copy -c copy -crf 50 file.mp4

trying to understand what the options mean

ffmpeg -i "http://host/folder/file.m3u8" -bsf:a aac_adtstoasc -vcodec copy -c copy -crf 50 file.mp4
-bsf:a aac_adtstoasc

bsf = (bit stream filter)
use aac_adtstoasc bsf for a audio streams, this is need if .m3u8 file consists with .ts files and output is .mp4
reference https://ffmpeg.org/ffmpeg-bitstream-filters.html#aac_005fadtstoasc
-c copy -vcodec copy

skip codec (encode and decode), just demux and mux
I guess .ts and .mp4, for video stream, they are both H.264 codec, just guess.
reference https://ffmpeg.org/ffmpeg.html#Stream-copy
-crf 50

reference https://trac.ffmpeg.org/wiki/Encode/H.264#CRFExample
the example shows -c:a copy did not re-encode, guess this option is not needed here.
And 0 is lossless, 23 is the default, and 51 is worst quality possible 😢


REF: https://gist.github.com/tzmartin/fb1f4a8e95ef5fb79596bd4719671b5d

REF2: https://github.com/homebrew-ffmpeg/homebrew-ffmpeg