user10371: On this page author reencodes MP4 from GoPro to MOV for "easy post processing". Why the processing becomes easier after that? The author also uses -sameq flag which is gone from ffmpeg without the explanation about what it did for H.264 blocks.

user1760: 
On this page author reencodes MP4 from GoPro to MOV for "easy post processing". Why the processing becomes easier after that?

The author provides no explanation and does not go into any detail of what he means by "post processing". What we know:

The author's ffmpeg command is using the encoder mpeg4 which will output MPEG-4 Part 2 video (like the old Xvid video).
The format of the GoPro video is probably H.264.

We must assume that the author believes H.264 is slower to decode than MPEG-4 Part 2 video, but that is not necessarily true. Or perhaps he believes that MOV container has some advantage over MP4 container when used with these formats; I can't guess what the supposed advantages would be since the containers are so similar.

The author also uses -sameq flag which is gone from ffmpeg without the explanation about what it did for H.264 blocks.

-sameq does not mean "same quality" (1)(2). The author's prodigious use of -sameq indicates that he doesn't really know what he is doing.
For H.264 specifically, when this option was still around (ages ago) it should have never been used when outputting H.264 because the option was designed for the "MPEG" quantizer scale which is not used by x264. Also, this option may have been ignored completely by libx264 at some time, but I can't recall exact details.

user3481: LordNeckbeard explained in his answer, why the given ffmpeg command line does not provide any known advantage.
But what - in general - could be reasons to transcode?

Available input codecs/containers of your NLE (video editing software)

There are hundreds of codec/container combinations out there, and maybe your NLE has just problems with the one that you have on your disk. Ex- and importing on different computers/NLEs/operating systems may introduce more unsupported combinations. 

Playback speed on the timeline

This is about inter-frame vs. intra-frame codecs. The article "Inter-frame vs Intra-frame" has a short explanation:


Basically, inter-frame encoding [...] means that a video file contains sets of grouped frames that reference each other in order to produce an image. [...]
  Intra-frame compression means that each frame is individual and contains all of its own information. The file size will be bigger, but the computer doesn't have to look around to find what it needs.

  Examples of inter-frame codecs are the H.264/mpeg family, while Apple ProRes and Avid DNxHD are intra-frame. GoPro Cineform may also be an intra-frame codec, but I couldn't find enough info to verify it.


But to make it short, you only have to consider transcoding, if your playback speed on the timeline is not smooth.
Special filters that should be applied before working with the NLE

This may be the case, if you have some filters/effects that your transcoding software can apply, but not your NLE. Or your NLE sometimes forgets these effects.


In conclusion, there are some good reasons to transcode, but you should know, if they apply in your case and are worth the effort. Then choose a high quality intra-frame codec, but not mpeg.

10371: <p>On <a href="https://gist.github.com/KonradIT/ee685aee15ba1c3c44b4#file-convert-multiple-files-md" rel="nofollow">this page</a> author reencodes MP4 from GoPro to MOV for "easy post processing". Why the processing becomes easier after that? The author also uses <code>-sameq</code> flag which is gone from <code>ffmpeg</code> without the explanation about what it did for H.264 blocks.</p>
 1760: <blockquote>
  <p>On this page author reencodes MP4 from GoPro to MOV for "easy post processing". Why the processing becomes easier after that?</p>
</blockquote>

<p>The author provides no explanation and does not go into any detail of what he means by "post processing". What we know:</p>

<ul>
<li><p>The author's <code>ffmpeg</code> command is using the encoder <code>mpeg4</code> which will output MPEG-4 Part 2 video (like the old Xvid video).</p></li>
<li><p>The format of the GoPro video is probably H.264.</p></li>
</ul>

<p>We must assume that the author believes H.264 is slower to decode than MPEG-4 Part 2 video, but that is not necessarily true. Or perhaps he believes that MOV container has some advantage over MP4 container when used with these formats; I can't guess what the supposed advantages would be since the containers are so similar.</p>

<blockquote>
  <p>The author also uses -sameq flag which is gone from ffmpeg without the explanation about what it did for H.264 blocks.</p>
</blockquote>

<p><code>-sameq</code> does not mean "same quality" (<a href="http://ffmpeg.org/faq.html#Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f" rel="nofollow noreferrer">1</a>)(<a href="https://superuser.com/a/478550/110524">2</a>). <strong>The author's prodigious use of <code>-sameq</code> indicates that he doesn't really know what he is doing.</strong></p>

<p>For H.264 specifically, when this option was still around (ages ago) it should have never been used when outputting H.264 because the option was designed for the "MPEG" quantizer scale which is not used by x264. Also, this option may have been ignored completely by libx264 at some time, but I can't recall exact details.</p>
 3481: <p>LordNeckbeard explained in his answer, why the given ffmpeg command line does not provide any known advantage.</p>

<p>But what - in general - could be reasons to transcode?</p>

<ol>
<li><p>Available input codecs/containers of your NLE (video editing software)</p>

<ul>
<li>There are hundreds of codec/container combinations out there, and maybe your NLE has just problems with the one that you have on your disk. Ex- and importing on different computers/NLEs/operating systems may introduce more unsupported combinations. </li>
</ul></li>
<li><p>Playback speed on the timeline
<ul>
<li>This is about inter-frame vs. intra-frame codecs. The article <a href="http://www.batchframe.com/quick-tips/tip.php?t=3" rel="nofollow" title="Inter-frame vs Intra-frame | BatchFrame.com">"Inter-frame vs Intra-frame"</a> has a short explanation:</p>

<blockquote>
  <p>Basically, inter-frame encoding [...] means that a video file contains sets of grouped frames that reference each other in order to produce an image. [...]
  Intra-frame compression means that each frame is individual and contains all of its own information. The file size will be bigger, but the computer doesn't have to look around to find what it needs.</li>
  </ul>
  Examples of inter-frame codecs are the H.264/mpeg family, while Apple ProRes and Avid DNxHD are intra-frame. GoPro Cineform may also be an intra-frame codec, but I couldn't find enough info to verify it.</p>
</blockquote>

<p>But to make it short, you only have to consider transcoding, if your playback speed on the timeline is not smooth.</p></li>
<li><p>Special filters that should be applied before working with the NLE</p>

<ul>
<li>This may be the case, if you have some filters/effects that your transcoding software can apply, but not your NLE. Or your NLE sometimes forgets these effects.</li>
</ul></li>
</ol>

<p>In conclusion, there are some good reasons to transcode, but you should know, if they apply in your case and are worth the effort. Then choose a high quality intra-frame codec, but not mpeg.</p>
