user25963: I understand there is a module built in FFmpeg which allows you to fade your clips in and out, however, no one really explains how to use the module with your own input. How do I simply fade both the audio and video in and out without re-encoding? (If that's possible)

user18155: Fading in is no problem, because you start from the timestamp 0 (or from other known timestamp or frame number), e.g. use:
ffmpeg -i input.mp4 -vf fade=in:0:d=5 -af afade=in:0:d=5 output.mp4

for 5-second fading in from the start of your clip. 
Ignore the error 

Only '-vf fade=in:0:d=5' read, ignoring remaining -vf options: Use ',' to separate filters

— see the answer of the question FFmpeg read, ignoring remaining -vf options: Use ',' to separate filters.
For fading out you have to subtract the time of fading out — e.g. 5 s — from the total duration of video or audio (you may find it with FFprobe). You got for example the timestamp 600 - 5 = 595 (from your 10-minutes long clip). Then add filters for fading out into the previous command:
ffmpeg -i input.mp4 -vf fade=in:0:d=5,fade=out:595:d=5 -af afade=in:0:d=5,afade=out=595:5 output.mp4


Notes:

Filtering always require re-encoding.
As in and 0 are defaults, you may shorten the command to
ffmpeg -i input.mp4 -vf fade=d=5,fade=out:595:d=5 -af afade=d=5,afade=out=595:5 output.mp4



25963: <p>I understand there is a module built in FFmpeg which allows you to fade your clips in and out, however, no one really explains how to use the module with your own input. How do I simply fade both the audio and video in and out without re-encoding? (If that's possible)</p>
 18155: <p>Fading in is no problem, because you start from the timestamp 0 (or from other known timestamp or frame number), e.g. use:</p>

<pre><code>ffmpeg -i input.mp4 -vf fade=in:0:d=5 -af afade=in:0:d=5 output.mp4
</code></pre>

<p>for 5-second fading in from the start of your clip. </p>

<p>Ignore the error </p>

<blockquote>
  <p>Only '-vf fade=in:0:d=5' read, ignoring remaining -vf options: Use ',' to separate filters</p>
</blockquote>

<p>— see the <a href="https://video.stackexchange.com/a/28215/18155">answer</a> of the question <a href="https://video.stackexchange.com/q/28214/18155">FFmpeg read, ignoring remaining -vf options: Use &#39;,&#39; to separate filters</a>.</p>

<p>For fading out you have to subtract the time of fading out — e.g. 5 s — from the total duration of video or audio (you may find it with FFprobe). You got for example the timestamp <code>600 - 5 = 595</code> (from your 10-minutes long clip). Then add filters for fading out into the previous command:</p>

<pre><code>ffmpeg -i input.mp4 -vf fade=in:0:d=5,fade=out:595:d=5 -af afade=in:0:d=5,afade=out=595:5 output.mp4
</code></pre>

<hr>

<p><em>Notes:</em></p>

<ol>
<li>Filtering always require re-encoding.</li>
<li><p>As <code>in</code> and <code>0</code> are defaults, you may shorten the command to</p>

<pre><code>ffmpeg -i input.mp4 -vf fade=d=5,fade=out:595:d=5 -af afade=d=5,afade=out=595:5 output.mp4
</code></pre></li>
</ol>
