Beginners guide to Bash, Linux commands and Transcoding. Learn Linux and Bash while transcoding your entire video collection to HEVC (x265) recursively.
What you’ll need:
- A directory full of Videos
- A Linux Machine – I am using Manjaro
- Ffmpeg with your hardware transcode compiled. I am using VA-Api with an AMD graphics card which can also be used with intel graphics. This isn’t a guide on how to compile ffmpeg with hardware transcoding enabled but you can either set up a software transcode, have the same set up as mine, or stay tuned for a future guide!
- Screen to run the script in the background
Getting what you need:
You can install what you need in Manjaro with:
pamac install ffmpeg-amd-full screen
Or Ubunutu
apt-get install ffmpeg screen
Preparing Script File
Start a new empty file with the touch command
touch ~/convert-video
change permissions of this file so that it can be executed by the owner (you) and your primary group. I’ll go a little more in-depth about permissions. You do this with the change mode command
chmod 774 ~/convert-video
The first 7 means read/write/execute permissions for the owner.
The second 7 means read/write/execute permission for the file’s group. This will be your primary group when you touched the file. You can see your primary group by using
id $USER
Mine shows gid=984(users)
The 4 means everyone else only has read capability on this file.
To verify permissions are set correctly:
ls -l ~/convert-video
Now open with a console text editor:
nano ~/convert-video
Start Scripting!
- First line we hash bang this to be a bash script
#!/bin/bash - Next we want to check to make sure the user designates the folder that all of our videos are located. We do this with an if-statement.
if [ -z $1 ];then echo Give target directory; exit 0;fi
This statement checks if the user put in anything as an argument when executing the script. If the user enters
~/convert-video /videofolder
everything is good and we continue. If they just enter~/convert-video - Next line we use the find command. We will search for all video extensions that do not have a HEVC added on by this script. Later in the script, we will add this to the file when transcoded so we can stop the script and resume it without transcoding the same videos. There are better ways of doing this (like using ffprobe to check the video format). I’m doing it this way to make the script simple to understand and fast.
find "$1" -depth \( -iname "*.mkv" -o -iname "*.mp4" -o -iname "*.mpg" -o -iname "*.mov" -o -iname "*.avi" -o -iname "*.iso" -o -iname "*.mpeg" \) -a -not -iname "*HEVC.mkv" | while read file ; do
The find command searches the folder the user inputted, checks all sub-folders with -depth and looks for all entered video extensions. -iname is case insensitive, -o means ‘or’, -a -not means ‘and not’ and we pipe ‘|’ that the rest of the code executes while going through our results. - We now create three variables based on a result from the find
directory=$(dirname "$file") oldfilename=$(basename "$file") newfilename=$(basename "${file%.*}")directory is the path of the file. Because we are converting all sub-folders, this could be different from file to file.
oldfilename is the full name of the movie with its old extension, i.e. movie.avi
newfilename is the file name with the extension removed. This would actually change movie.avi to movie, as we don’t want .avi to be part of the new filename - Next line we do the conversion with ffmpeg
nice -n 15 ffmpeg -threads 4 -i "$directory/$oldfilename" -vaapi_device /dev/dri/renderD128 -vcodec hevc_vaapi -vf format='nv12-f matroska "$directory/$newfilename - HEVC.mkv" </dev/null
nice -n 15
-threads 4
-i "$directory/$oldfilename"
this uses our variables for the video input.
-vaapi_device /dev/dri/renderD128 -vcodec hevc_vaapi -vf format='nv12|vaapi,hwupload'
This is the information specific to my AMD, open source driver and to HEVC (hevc_vaapi). During a software encode to hevc, this all can be replaced with-c:v libx265
-qp:v 20
sets the quality level. Lower, the higher the quality but larger file. 19, 20 and 21 are ok choices to look at.
-crf 26
is the software encode command you want with
-crf 28
being default quality.
-c:a libvorbis -qscale 5 -ac 6
is the Sound. Vorbis is the lossy sound file we are converting to. We have a quality of 5 with 10 being the highest. Something between 5-7 is good but I’ve found 5 to be very good. -ac 6 converts this to 5.1 surround sound. You can either omit this setting or set it to your sound system. Note that converting a file from something like stereo (2.1) to 5.1 will increase size.
matroska "$directory/$newfilename - HEVC.mkv
And finally this is our output file. It is a matroska container with – HEVC at the end. This is so this script and us know which videos have been converted.
# rm "$directory/$oldfilename"
This is a commented out remove command. It is commented out so it is not executed normally. In order to uncomment it (remove the hash at the front), you must understand what will happen. Any Failed Transcode will delete your original file. I haven’t had a good video file fail yet but let it be known. And Any Attempt in Stopping of the script with ctl+c will only stop that ffmpeg instance right there, delete the original file and leave with what you got so far then move on to the next file. - You must stop the script with ctl-z and delete the file it was creating ending in HEVC.mkv before starting it again
All that is necessary if you uncomment this rm statement. This can easily be considered a bug but much more elaborate scripting is required to make it work differently.
done
Complete Script
#!/bin/bash
# convert video types to hevc recursively
# By Michael Gray
#####################################
if [ -z $1 ];then echo Give target directory; exit 0;fi
find "$1" -depth \( -iname "*.mkv" -o -iname "*.mp4" -o -iname "*.mpg" -o -iname "*.mov" -o -iname "*.avi" -o -iname "*.iso" -o -iname "*.mpeg" \) -a -not -iname "*HEVC.mkv" | while read file ; do
directory=$(dirname "$file")
oldfilename=$(basename "$file")
newfilename=$(basename "${file%.*}")
nice -n 15 ffmpeg -threads 4 -i "$directory/$oldfilename" -vaapi_device /dev/dri/renderD128 -vcodec hevc_vaapi -vf format='nv12|vaapi,hwupload' -qp:v 20 -c:a libvorbis -qscale 5 -ac 6 -f matroska "$directory/$newfilename - HEVC.mkv" </dev/null
# rm "$directory/$oldfilename"
doneRunning The Script
This script will take a very long time to transcode many videos. To make it run in the background
screen -S convert-video
then run it with
~/convert-video /media/yourvideos
Exit the screen with ctl-a then d
To check on the progress, screen -r convert-video
Also remember if you stop your script with ctl-z, also delete whatever partial output it was creating.
