user5490: I've added different language subtitles to individual m4v movies, and they show fine when selecting the subtitle track in both Quicktime and VLC. I would like to have them so that the subtitles display by default. Any way to do this?

user3295: Afaik apart from Blu-ray's and DVD's only MKV supports forced subtitles.
If you want the subtitles to be "burned" into the video. Meaning they are part of the pixel frames you can use a tool like ffmpeg. A nice tutorial specific to mp4/m4v can be found here: http://forum.videohelp.com/threads/277706-How-to-add-subtitles-permanently-to-existing-mp4-h-264-file?p=2305682&viewfull=1#post2305682
MP4 definitely can not show forced subtitles in software. There might be another format other than MKV that supports forced subtitles that I don't know of but mp4 definitely doesn't have that in its specs.

user3912: You can use MP4Box 0.6.2-DEV-rev453 (May 2016) or higher to do this:
mp4box -add alfa.mp4 -add bravo.srt:txtflags=0xC0000000 -new charlie.mp4

Example
This will mark the subtitle stream in the output file as forced.
However, this mark will only be recognized starting with these versions of
programs:

MPC-HC 1.7.10.207 (May 2016)

VLC media player 3.0.0-20161101 (Nov 2016)



I have seen mentions to this post on the FFmpeg mailing list about a
patch that implements disposition for FFmpeg:
ffmpeg -i alfa.mp4 -i bravo.srt -c copy -c:s mov_text -disposition:s forced charlie.mp4

However after having tried it with both "forced" and "default", the subtitles
marked by FFmpeg are not recognized as forced by either MPC-HC or VLC.

5490: <p>I've added different language subtitles to individual m4v movies, and they show fine when selecting the subtitle track in both Quicktime and VLC. I would like to have them so that the subtitles display by default. Any way to do this?</p>
 3295: <p>Afaik apart from Blu-ray's and DVD's only MKV supports forced subtitles.
If you want the subtitles to be "burned" into the video. Meaning they are part of the pixel frames you can use a tool like ffmpeg. A nice tutorial specific to mp4/m4v can be found here: <a href="http://forum.videohelp.com/threads/277706-How-to-add-subtitles-permanently-to-existing-mp4-h-264-file?p=2305682&amp;viewfull=1#post2305682" rel="nofollow">http://forum.videohelp.com/threads/277706-How-to-add-subtitles-permanently-to-existing-mp4-h-264-file?p=2305682&amp;viewfull=1#post2305682</a></p>

<p>MP4 definitely can not show forced subtitles in software. There might be another format other than MKV that supports forced subtitles that I don't know of but mp4 definitely doesn't have that in its specs.</p>
 3912: <p>You can use <a href="//gpac.wp.mines-telecom.fr/downloads/gpac-nightly-builds" rel="nofollow noreferrer">MP4Box 0.6.2-DEV-rev453</a> (May 2016) or higher to do this:</p>
<pre><code>mp4box -add alfa.mp4 -add bravo.srt:txtflags=0xC0000000 -new charlie.mp4
</code></pre>
<p><a href="//github.com/svnpenn/a/blob/af30667/etc/mp4box.sh#L27-L28" rel="nofollow noreferrer">Example</a></p>
<p>This will mark the subtitle stream in the output file as forced.</p>
<p><strong>However</strong>, this mark will only be recognized starting with these versions of
programs:</p>
<ul>
<li><p><a href="//nightly.mpc-hc.org" rel="nofollow noreferrer">MPC-HC 1.7.10.207</a> (May 2016)</p>
</li>
<li><p><a href="//nightlies.videolan.org" rel="nofollow noreferrer">VLC media player 3.0.0-20161101</a> (Nov 2016)</p>
</li>
</ul>
<hr />
<p>I have seen mentions to <a href="//ffmpeg.org/pipermail/ffmpeg-devel/2015-January/167371.html" rel="nofollow noreferrer">this post</a> on the FFmpeg mailing list about a
patch that implements disposition for FFmpeg:</p>
<pre><code>ffmpeg -i alfa.mp4 -i bravo.srt -c copy -c:s mov_text -disposition:s forced charlie.mp4
</code></pre>
<p>However after having tried it with both &quot;forced&quot; and &quot;default&quot;, the subtitles
marked by FFmpeg are not recognized as forced by either MPC-HC or VLC.</p>
