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rfraimow 2015-11-18 20:00:26 -05:00
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<!-- ends Split audio and video tracks -->
<!-- Transcode to h.264 -->
<span data-toggle="modal" data-target=".transcode_h264"><button type="button" class="btn btn-default" data-toggle="tooltip" data-placement="bottom" title="Transcode to an h.264 access file">Transcode to h.264</button></span>
<div class="modal fade transcode_h264" tabindex="-1" role="dialog" aria-labelledby="myLargeModalLabel">
<div class="modal-dialog modal-lg">
<div class="modal-content">
<!-- where the text goes -->
<div class="well">
<h3>Transcode to h.264</h3>
<p><code>ffmpeg -i [input file] -vcodec libx264 -acodec copy [output file.mp4]</code></p>
<p>This command takes an input file and transcodes it to h.264 with an .mp4 wrapper, keeping the audio the same codec as the original. The libx264 codec defaults to a “medium” preset for compression quality and a CRF of 23. CRF stands for constant rate factor and determines the quality and file size of the resulting h.264 video. A low CRF means high quality and large file size; a high CRF means the opposite. </p>
<ul>
<li>ffmpeg: Calls the program ffmpeg</li>
<li>-i: Tells ffmpeg to expect an input file</li>
<li>[input file]: Tells ffmpeg the location of the file you want to process</li>
<li>-vcodec libx264: Tells ffmpeg to change the video codec of the file to h264 -acodec copy: tells ffmpeg not to change the audio codec</li>
<li>[output file.mp4]: Specifies the name and location of the new file, including the desired codec extension</li>
</ul>
<p>In order to use the same basic command to make a higher quality file, you can add some of these presets:</p>
<p><code>ffmpeg -i [input file] -vcodec libx264 -acodec copy -preset veryslow -crf 18 [output file.mp4]</code></p>
<li>-preset veryslow: This option tells ffmpeg to use the slowest preset possible for the best compression quality</li>
<li>-crf 18: Specifying a lower CRF will make a larger file with better visual quality</li>
<p>libx264 also defaults to 4:2:2 chroma subsampling. Some versions of Quicktime can't read x264 files in 4:2:2. In order to allow the video to play in all Quicktime players, you can specify 4:2:0 chroma subsampling instead:</p>
<p><code>ffmpeg -i [input file] -vcodec libx264 -pix_fmt yuv420p -acodec copy -preset veryslow -crf 18 [output file.mp4]</code></p>
<li>-pix_fmt yuv420p: Specifies a pixel format of YUV 4:2:0 to allow the file to play in a standard Quicktime player</li>
</div>
</div>
</div>
</div>
<!-- ends Transcode to h.264 -->
</div> <!-- end this well (and this ends well) -->
</div> <!-- row -->