Convert Unix epoch timestamp to human-readable date

In:

date -r 1581700603

Out:

Fri Feb 14 18:16:43 CET 2020

Source:
https://unix.stackexchange.com/questions/2987/how-do-i-convert-an-epoch-timestamp-to-a-human-readable-format-on-the-cli

How to concatenate videos with ffmpeg

This one works for me:

ffmpeg -i input1.mp4 -i input2.webm -i input3.mov \
-filter_complex "[0:v:0][0:a:0][1:v:0][1:a:0][2:v:0][2:a:0]concat=n=3:v=1:a=1[outv][outa]" \
-map "[outv]" -map "[outa]" output.mkv

Reference: https://trac.ffmpeg.org/wiki/Concatenate

It assumes the videos have the same size and TBR. To transpose a video when one is vertical and another is horizontal, see here.

When video TBRs are different, it may come up with the strange message:

"More than 1000 frames duplicated"

When this happens, try adding "-vsync 2" to the command. Reference: https://stackoverflow.com/questions/62822889/ffmpeg-filter-complex-concat-never-completes. It worked for me.

How to transpose a video with ffmpeg

ffmpeg -i input.mp4 -vf "transpose=1" output.mp4

or

ffmpeg -i input.mp4 -vf "transpose=clock" output.mp4

for one 90-deg clockwise rotation.

Reference: https://ostechnix.com/how-to-rotate-videos-using-ffmpeg-from-commandline/#:~:text=FFMpeg%20has%20a%20feature%20called,flip%20them%20vertically%20and%20horizontally.&text=Here%2C%20transpose%3D1%20parameter%20instructs,video%20by%2090%20degrees%20clockwise.

Combine image + audio file to make a video

Source: https://video.stackexchange.com/questions/5291/how-to-make-a-video-from-a-still-image-and-an-audio-file

I tried at least 5 commands from different sites, and only this one worked well enough for me - about 37x speed, waitable.

ffmpeg -loop 1 -f image2 -r 2 -i image.jpg -i audio.m4a -c:v libx264 -c:a copy -shortest video.mp4

How to prevent Automounting of Volumes (USB drives, optical discs, etc) upon connecting on Mac OS X

 https://discussions.apple.com/docs/DOC-7942

1. diskutil info /Volumes/<volume that shouldn't be mounted>
2. Get UUID from output from above step 1.
3. sudo /etc/vifs
4. Add this to the file:
1. UUID=<LONG-UUID-LIKE-F77F-3F72-A6C2-26676F39B7CE> none hfs rw,noauto
5. sudo automount -vc

Done! Worked for me!

ffmpeg aac -> mp3 conversion

It seems that it isn't easy to handle aac/m4a files in sox anymore. Online help threads suggest using ffmpeg to convert it to mp3 instead:

 ffmpeg -i input.m4a -c:a libmp3lame -q:a 8 output.mp3

Reference link: https://askubuntu.com/questions/1200430/how-to-convert-m4a-audio-files-to-mp3-use-command-line

watch

Have you ever wanted to run some command periodically, usually to wait for some change in the result (like waiting for some ACL to be propagated, a price value to change, etc)?

Seek no more! Do you know the "watch" unix command?

watch -n 60 <command>

This will run <command> every 60 seconds! And you can inspect the output every time it does.

Its usage is quite simple. The help output is:

Usage:

 watch [options] command

Options:

  -b, --beep             beep if command has a non-zero exit

  -c, --color            interpret ANSI color and style sequences

  -d, --differences[=<permanent>]

                         highlight changes between updates

  -e, --errexit          exit if command has a non-zero exit

  -g, --chgexit          exit when output from command changes

  -n, --interval <secs>  seconds to wait between updates

  -p, --precise          attempt run command in precise intervals

  -t, --no-title         turn off header

  -x, --exec             pass command to exec instead of "sh -c"

 -h, --help     display this help and exit

 -v, --version  output version information and exit

Useful command to know!