user1940: I have an ASS as the subtitle stream (with these fonts: - Orotund, jagb_.tff, jagw_.ttf, JUST.ttf, Gabrielle.ttf) in an MKV.
What technique should I use to hardsub this subtitle stream onto the MPEG4 (ISO/AVC) without losing quality?
Thanks for all suggestions

user37172: ffmpeg has an amazing article on burning the subs into the videos.
I trust ffmpeg to be very careful with (the lack of) quality loss.
Given you are dealing with ASS, here are the important bits,

You can burn text subtitles (hardsubs) with one of two filters: subtitles or ass.
ass filter
Same as the subtitles filter, except that it doesn’t require libavcodec and libavformat to work. This filter requires ffmpeg to be compiled with --enable-libass. On the other hand, it is limited to ​ASS (Advanced Substation Alpha) subtitles files. See the ​ass video filter documentation for more details.
ffmpeg -i video.avi -vf "ass=subtitle.ass" out.avi

If your subtitle is in SubRip, MicroDVD or any other supported text subtitles, you have to convert it to ASS before using this filter:
ffmpeg -i subtitle.srt subtitle.ass

Windows users will have to ​setup font paths to get libass to work


1940: <p>I have an ASS as the subtitle stream (with these fonts: - Orotund, jagb_<strong><em>.tff, jagw</em>_</strong>.ttf, JUST.ttf, Gabrielle.ttf) in an MKV.</p>

<p>What technique should I use to hardsub this subtitle stream onto the MPEG4 (ISO/AVC) without losing quality?</p>

<p>Thanks for all suggestions</p>
 37172: <p><a href="https://trac.ffmpeg.org/wiki/HowToBurnSubtitlesIntoVideo" rel="nofollow noreferrer">ffmpeg</a> has an amazing article on burning the subs into the videos.</p>
<p>I trust ffmpeg to be very careful with (the lack of) quality loss.</p>
<p>Given you are dealing with ASS, here are the important bits,</p>
<blockquote>
<p>You can burn text subtitles (hardsubs) with one of two filters: subtitles or ass.</p>
<p>ass filter</p>
<p>Same as the subtitles filter, except that it doesn’t require libavcodec and libavformat to work. This filter requires ffmpeg to be compiled with --enable-libass. On the other hand, it is limited to ​ASS (Advanced Substation Alpha) subtitles files. See the ​ass video filter documentation for more details.</p>
<pre><code>ffmpeg -i video.avi -vf &quot;ass=subtitle.ass&quot; out.avi
</code></pre>
<p>If your subtitle is in SubRip, MicroDVD or any other supported text subtitles, you have to convert it to ASS before using this filter:</p>
<pre><code>ffmpeg -i subtitle.srt subtitle.ass
</code></pre>
<p>Windows users will have to ​setup font paths to get libass to work</p>
</blockquote>
