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!

Noise removal (sox) and fixing video/audio merge (ffmpeg)

When you have some audio and it's noisy, remove the noise with this:

# Create background noise profile from mp3
/usr/bin/sox noise.mp3 -n noiseprof noise.prof

# Remove noise from mp3 using profile
/usr/bin/sox input.mp3 output.mp3 noisered noise.prof 0.21

Referral:
https://unix.stackexchange.com/questions/425853/how-to-clear-background-noises-with-sox

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When you're merging audio and video with ffmpeg, and your video ends up silent, remember to map the video and audio streams from the two files explicitly:

ffmpeg -y -i merged.mp4 -i combined.mp3 -c:a aac -map 0:v -map 1:a output.mp4

Referral:
https://unix.stackexchange.com/questions/425853/how-to-clear-background-noises-with-sox

Concatenate images with ImageMagick

Quick and easy:

convert clp.png clp.png clp.png clp.png clp.png clp.png clp.png clp.png -append page.png

Reference: http://www.imagemagick.org/discourse-server/viewtopic.php?t=19885

Trim a video

...with ffmpeg!

ffmpeg -i movie.mp4 -ss 00:00:03 -t 8 -async 1 cut.mp4

Easy peasy. Trims a video from second 3 for a length of 8 seconds. The -async 1 is optional... maybe it speeds it up with parallel processing?

Source link. Thanks!

Remote pbcopy

Check it out!

http://brettterpstra.com/2014/02/19/remote-pbcopy-on-os-x-systems/

The actual steps are at (referenced from first link):
https://seancoates.com/blogs/remote-pbcopy/

Ghostscript JPG -> PDF

I'm not sure why I never posted this, but this is very useful when making documents from photos.

HOW TO CONVERT A JPG TO A PDF FILE:

gs \
 -sDEVICE=pdfwrite \
 -o outfile.pdf \
  /usr/local/share/ghostscript/8.71/lib/viewjpeg.ps \
 -c \(infile.jpg\) viewJPEG

Notice the \(...\) around the filename. They're important!

Also, the "/usr/local/share/ghostscript/8.71/lib/viewjpeg.ps" path varies, depending on the current installed version of ghostscript. Run the following to find your correct version:

find /usr/local/share/ghostscript -name viewjpeg.ps

Ref: http://stackoverflow.com/questions/4283245/using-ghostscript-to-convert-jpeg-to-pdf