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multimedia.md

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MultiMedia

Media file analysis, editing, transcoding and conversions.

Image

Convert Webp to PNG format

medium.com doesn't support using newer webp format images on the site so you need to convert them first:

On Mac, install the dwebp homebrew package:

brew install webp

Convert the image:

dwebp "$name.webp" -o "$name.png"

or shorter and safer using function in DevOps-Bash-tools repo:

webp_to_png "$name.webp"

This function adds safety to not overwrite the destination file if it already exists because dwebp will blindly overwrite the -o outfile.

Join Two Images Together

Useful to create memes.

Since images can have different widths and end up with whitespace around the smaller image, use this script from the DevOps-Bash-tools repo to stack joins them after matching their widths so they align correctly:

image_join_stack.sh "$top_image" "$bottom_image" "joined_image.png"

Inspect Image File Metadata

exiftool "$file"

Identify command from imagemagick is more verbose:

identify -verbose "$file"

Exiv2 is less reliable:

exiv2

Look for Watermarks

magick "$file" -edge 1 output.jpg

Then visually inspect the output.jpg which is blacked out to see sillouttes more easily.

You can also try converting to black & white (grey):

magick "$file" -channel Red -separate output.jpg

Steghide

This on only works if you've hidden something inside the image and know the password to extact it:

steghide info "$file"

Looks like this is removed from Mac Homebrew, launch it in a debian docker container instead:

steghide extract -sf "$file"

Video

Get the resolution and other details like codec for a video file

ffmpeg -i "$file"

or

ffprobe "$file"

Transcode mkv into standard mp4 for smart TVs to play

ffmpeg -i "input.mkv" "output.mp4"

There is an automated script in the DevOps-Bash-tools repo's media/ directory to iterate many files easily:

mkv_to_mp4.sh *.mkv

or find all mkv files recursively under the given directory and convert them (retains originals), in this case the $pwd denoted by a dot:

mkv_to_mp4.sh .

Video Clipping

Create a clip from a video file using ffmpeg args:

  • -ss <offset> and -to <duration> where duration is integer seconds or HH:MM:SS format
  • -c copy - -c specifies codec, copy is quick and cheap codec compared to transcoding
ffmpeg -i input_vid.mp4 -ss 00:08:35.0 -t 72 -c copy output_vid.mp4

or using time format -to 00:01:12 which is the same as 72 seconds from offset start.

Inspect Media File

ffprobe $file
exiftool $file
mediainfo $file
mediainfo --fullscan $file
avprobe $file
mplayer -vo null -ao null -identify -frames 0 $file
tovid id $file

Audio

MP3 metadata editing

Use the id3v2 program to set metadata on mp3 files.

Useful to group a bunch of mp3 files for an audiobook.

Set the --author / -a and --album / -A tags at once so Mac's Books.app groups them properly into one audiobook:

id3v2 -a "MyAuthor" -A "MyAlbum" *.mp3

The scripts mp3_set_artist.sh and mp3_set_album.sh in the DevOps-Bash-tools repo's media/ directory make it slightly easier.

Set the --track number for each mp3 file, so they play in the right order:

i=0
for x in *.mp3; do
  ((i+=1))
  id3v2 -T $i "$x"
done

The scripts mp3_set_track_order.sh and mp3_set_track_name.sh in the DevOps-Bash-tools repo's media/ directory make this slightly easier.

Recursively set Artist/Album - XXX: Danger, use only in an audiobook subdirectory, otherwise it'll ruin the metadata of your MP3 library!

find . -maxdepth 2 -iname '*.mp3' |
{
  i=0
  while read mp3; do
    ((i+=1))
    id3v2 -a "MyAuthor" -A "MyAlbum" "$mp3"
  done
}

Recursively set Track Order - for subdirectories eg. CD1, CD2 etc... XXX: use with care - misused at the top it'd ruin your MP3 library's metadata:

find . -maxdepth 2 -iname '*.mp3' |
{
  i=0
  while read mp3; do
    ((i+=1))
    id3v2 -T $i "$mp3"
  done
}

MediaBox Setup

This is old from 2010 and probably needs some updates:

aptitude install nvidia-glx-173
aptitude -y purge samba
aptitude -y purge bluez bluetooth gnome-bluetooth bluez-utils
aptitude -y purge cups bluez-cups cups-driver-gutenprint foo2zjs foomatic-db foomatic-db-engine ghostscript-cups hpijs hplip openprinting-ppds pxljr splix
apt-get -y purge evolution evolution-common
aptitude -y purge openssh-server
dpkg -l | grep openoffice | awk '{print $2}' | xargs aptitude -y purge language-support-en language-support-writing-en python-uno
aptitude -y install sysstat
aptitude -y install unrar
aptitude -y install libdvdread4
/usr/share/doc/libdvdread4/install-css.sh

Remote control

as root:

mkdir /var/run/lirc # it wouldn't create it and it wouldn't start without it on ubuntu
aptitude -y install dvb-utils

Cyberlink remote shows us as /dev/input/event3 according to google.

Can cat that or after installing dvb-utils, can do:

evtest /dev/input/event3

except dvb-utils has no install candidate and tells you to instead get dvb-apps which is already installed and doesn't have evtest, only the c file for it

less /proc/bus/input/devices

remote control is detected as a keyboard so a bunch of stuff just works out of the box. Should use xmodmap to add the remaining buttons to do things I want

Ported from private Knowledge Base pages 2010+