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I had to convert some MKV video files into MP4 format with embedded (rendered) subtitles. This would not be a problem if not the external ASS subs that I had. HandBrakeCLI can easily convert between those formats but it can use embedded ASS file (from MKV video) or provided SRT. There is no way to use an external ASS subtitles file. Luckily there is a quite simple solution for that issue: we can just remove original MKV video subtitles, add ours and then use HandBrakeCLI to convert the video.

Replacing the ASS MKV subtitles with our own

First we need to remove the original ASS subtitles that are stored in MKV file:

mkvmerge --no-subtitles source.mkv -o target.mkv

This will copy MKV file but will remove subtitles.

After that, we need to add our ow ASS file (subtitles.ass):

mkvmerge -o target_with_subs.mkv target.mkv -D -A subtitles.ass

Now we have a MKV file with our ASS subtitles, that we can use to create MP4 file.

Creating MP4 file with embedded (hardcoded) subtitles

Convertion is really simple:

HandBrakeCLI -i target_with_subs.mkv -o result.mp4 -e x264 -q 20 -B 160\
 --x264-preset medium --two-pass -O --turbo --subtitle "1" \
 --subtitle-burn "1" --srt-codeset utf8

Simple one line long command and 30 minutes later you have your MP4 file with hardsubs.

Jenkins in an awesome integration server, that can be used for free. However, having it on a non-standard www port, without a SSL, might be a problem. Accessing it from a public network might create a security threat. If you've got a Apache in front of your server, you can easily provide a secured proxy to Jenkins.

To do so, you need to create a VirtualHost for Apache, which will contain both: Proxy and SSL. Also it would be wise, to redirect standard HTTP requests.

VirtualHost to redirect from HTTP to HTTPS

So, first lets create our HTTP VirtualHost and let's redirect it to HTTPS version:

<VirtualHost *:80>
  ServerName jenkins.my.domain
  ServerAlias www.jenkins.my.domain

  RewriteEngine on
  ReWriteCond %{SERVER_PORT} !^443$
  RewriteRule ^/(.*) https://%{HTTP_HOST}/$1 [NC,R,L]
</VirtualHost>

SSL keys

To get things started, we will need a key. To generate it, follow given steps (as root):

sudo su # or any other way to be a root
cd /etc/apache2/
mkdir ssl
cd ssl/
mkdir crt
mkdir key
openssl req -new -x509 -days 365 -keyout key/jenkins.key -out crt/jenkins.crt -nodes -subj  '/O=Jenkins/OU=Jenkins/CN=jenkins.my.domain'

Just remember to replace all the domain references from "jenkins.my.domain" to an appropriate one. After you execute the above commands, you should have a ssl key and ssl cert generated.

Installing Apache necessary mods

To create a SSL Proxy pass we need to install some Apache mods (still as a root):

a2enmod proxy
a2enmod proxy_http
a2enmod rewrite
a2enmod ssl

/etc/init.d/apache2 restart

HTTPS Jenkins Virtual Host

And finally, the virtual host for secured Jenkins proxy pass:

<VirtualHost *:443>
  ServerName jenkins.my.domain
  ServerAlias www.jenkins.my.domain

  SSLEngine On
  SSLCertificateFile    /etc/apache2/ssl/crt/jenkins.my.domain.crt
  SSLCertificateKeyFile /etc/apache2/ssl/key/jenkins.my.domain.key

  ProxyRequests     Off
  ProxyPass         /  http://localhost:8080/
  ProxyPassReverse  /  http://localhost:8080/
  ProxyPassReverse  /  http://my.jenkins.host/
  <Proxy http://localhost:8080/*>
    Order allow,deny
    Allow from all
  </Proxy>
  ProxyPreserveHost on
</VirtualHost>

Category: Linux

Converting MKV video file to MP4 with hardsubs (embedded subtitles) on Linux (Ubuntu)