This work is licensed under a <ahref="https://creativecommons.org/licenses/by/4.0/"target="_blank">Creative Commons Attribution 4.0 International License</a>.
</p>
<h3>Sister projects</h3>
<h3>Sibling projects</h3>
<p><ahref="https://dd388.github.io/crals/"target="_blank">Script Ahoy</a>: Community Resource for Archivists and Librarians Scripting</p>
<p><ahref="https://datapraxis.github.io/sourcecaster/"target="_blank">The Sourcecaster</a>: an app that helps you use the command line to work through common challenges that come up when working with digital primary sources.</p>
<p><ahref="https://pugetsoundandvision.github.io/micropops/"target="_blank">Micropops</a>: One liners and automation tools from Moving Image Preservation of Puget Sound</p>
<p><ahref="https://amiaopensource.github.io/cable-bible/"target="_blank">Cable Bible</a>: A Guide to Cables and Connectors Used for Audiovisual Tech</p>
<p><ahref="https://eaasi.gitlab.io/qemu-qed/"target="_blank">QEMU QED</a>: instructions for using QEMU (Quick EMUlator), a command line application for computer emulation and virtualization</p>
<p><ahref="https://eaasi.gitlab.io/program_docs/qemu-qed/"target="_blank">QEMU QED</a>: instructions for using QEMU (Quick EMUlator), a command line application for computer emulation and virtualization</p>
<p><ahref="https://amiaopensource.github.io/ffmpeg-artschool/"target="_blank">ffmpeg-artschool</a>: An AMIA workshop featuring scripts, exercises, and activities to make art using FFmpeg</p>
</div>
<divclass="well">
@@ -337,6 +338,38 @@
</div>
<!-- ends Transcode to H.264 -->
<!-- Transcode to H.264 or H.265 using the GPU -->
<labelclass="recipe"for="transcode_gpu">Transcode to H.264/H.265 using the GPU</label>
<p>This command takes an input file and transcodes it to H.264 using the encoding functionality of an Nvidia GPU (without transcoding the audio). If you're using H.264 with AAC or AC3 audio, you can output to an .mp4 file; if you're using HEVC and/or more exotic audio, you should output to .mkv. While Nvidia's fixed-function hardware can be 10x as performant as encoding on the CPU, it requires a few more parameters in order to optimize quality at lower bitrates.</p>
<dl>
<dt>ffmpeg</dt><dd>starts the command</dd>
<dt>-i <em>input_file</em></dt><dd>path, name and extension of the input file</dd>
<dt>-c:v <em>h264_nvenc</em></dt><dd>tells FFmpeg to encode the video stream as H.264 using Nvidia's encoder.</dd>
<dt>-preset <em>llhq</em></dt><dd>uses the "low latency, high quality" encoding preset, a good default when working with nvenc.</dd>
<dt>-rc:v <em>vbr_hq</em></dt><dd>means "variable bitrate, high quality," allowing you to set a minimum and maximum bitrate for the encode.</dd>
<dt>-cq:v <em>19</em></dt><dd>is the same as the CRF quality level specified using x264 or other CPU-based encoders, where 0 is lossless, 51 is the worst possible quality, and values from 18-23 are typical.</dd>
<dt>-b:v <em>8000k -maxrate:v 12000k</em></dt><dd>corresponds to a minimum bitrate of 8 megabits (8000k) per second, and a maximum of 12 megabits per second. nvenc is not as good at estimating bitrates as CPU-based encoders, and without this data, will occasionally choose a visibly lower bitrate. The 8-12 mbit range is generally a good one for high-quality 1080p h264.</dd>
<dt>-profile:v <em>high</em></dt><dd>uses the "high quality" profile of h264, something that's been baked in to the spec for a long time so that older players can declare compatibility; almost all h264 video now uses high.</dd>
<dt>-c:a <em>copy</em></dt><dd>will skip reencoding the audio stream, and copy the audio from the source file.</dd>
<dt><em>output_file</em></dt><dd>path, name and extension of the output file</dd>
</dl>
<p>In order to encode to HEVC instead, and optionally transcode the audio, you can try changing the command like this:</p>
<dt>-c:v <em>hevc_nvenc</em></dt><dd>encodes to HEVC (also called H.265), a more efficient codec supported on GPUs from approximately 2015 and newer.</dd>
<dt>-b:v <em>5000k -maxrate:v 8000k</em></dt><dd>specifies a slightly lower bitrate than when using h264, per HEVC's greater efficiency.</dd>
<dt>-profile:v <em>main10</em></dt><dd>declares the "main10" profile for working with HEVC; one of the primary advantages of this codec is better support for 10-bit video, enabling consumer HDR.</dd>
<dt>-c:a <em>aac</em></dt><dd>reencodes the audio to AAC with default parameters, a very common and widely supported format for access copies.</dd>
</dl>
<p>Much of the information in this entry was taken from <ahref="https://superuser.com/a/1236387"target="_blank">this superuser.com post</a> provided by an Nvidia developer, one of the best sources of information on the ffmpeg Nvidia encoders.</p>
<pclass="link"></p>
</div>
<!-- ends Transcode to H.264 or H.265 using the GPU -->
<!-- H.264 from DCP -->
<labelclass="recipe"for="dcp_to_h264">Transcode from DCP to an H.264 access file</label>
<p>This command takes an input file and transcodes it to Ogg/Theora in an .ogv wrapper with 690k video bitrate.</p>
<p><strong>Note:</strong> FFmpeg must be installed with support for Ogg Theora. If you are using Homebrew, you can check with <code>brew info ffmpeg</code> and then update it with <code>brew upgrade ffmpeg --with-theora --with-libvorbis</code> if necessary.</p>
<dl>
<dt>ffmpeg</dt><dd>starts the command</dd>
<dt>-i <em>input file</em></dt><dd>path, name and extension of the input file</dd>
@@ -723,7 +755,7 @@
<li>In the sound filter <code>atempo</code> the numerator <code>output_fps</code> sets the output speed and the denominator <code>input_fps</code> sets the input speed; both values are given in frames per second.</li>
</ul>
The different filters in a complex filter can be divided either by comma or semicolon. The quotation marks allow to insert a space between the filters for readability.</dd>
<dt>-map "[v]"</dt><dd>maps the video stream and:</dd>
<dt>-map "[v]"</dt><dd>maps the video stream and</dd>
<dt>-map "[a]"</dt><dd>maps the audio stream together into:</dd>
<dt><em>output_file</em></dt><dd>path, name and extension of the output file</dd>
<p>This command takes two or more files of the same file type and joins them together to make a single file. All that the program needs is a text file with a list specifying the files that should be joined. However, it only works properly if the files to be combined have the exact same codec and technical specifications. Be careful, FFmpeg may appear to have successfully joined two video files with different codecs, but may only bring over the audio from the second file or have other weird behaviors. Don’t use this command for joining files with different codecs and technical specs and always preview your resulting video file!</p>
<p>This command takes two or more files of the same file type and joins them together to make a single file. All that the program needs is a text file with a list specifying the files that should be joined. If possible, run the command from the same directory where the files and the text file reside. Otherwise you'll have to use <code>-safe 0</code>, see below for more information. However, it only works properly if the files to be combined have the exact same codec and technical specifications. Be careful, FFmpeg may appear to have successfully joined two video files with different codecs, but may only bring over the audio from the second file or have other weird behaviors. Don’t use this command for joining files with different codecs and technical specs and always preview your resulting video file!</p>
<dl>
<dt>ffmpeg</dt><dd>starts the command</dd>
<dt>-f concat</dt><dd>forces ffmpeg to concatenate the files and to keep the same file format</dd>
<dt>-i <em>mylist.txt</em></dt><dd>path, name and extension of the input file. Per the <ahref="https://ffmpeg.org/ffmpeg-formats.html#Options"target="_blank">FFmpeg documentation</a>, it is preferable to specify relative rather than absolute file paths, as allowing absolute file paths may pose a security risk.<br>
This text file contains the list of files to be concatenated and should be formatted as follows:
<pre>file '<em>./first_file.ext</em>'
file '<em>./second_file.ext</em>'
This text file contains the list of files (without their absolute path) to be concatenated and should be formatted as follows:
<pre>
file '<em>first_file.ext</em>'
file '<em>second_file.ext</em>'
. . .
file '<em>./last_file.ext</em>'</pre>
file '<em>last_file.ext</em>'
</pre>
In the above, <strong>file</strong> is simply the word "file". Straight apostrophes ('like this') rather than curved quotation marks (‘like this’) must be used to enclose the file paths.<br>
<strong>Note:</strong> If specifying absolute file paths in the .txt file, add <code>-safe 0</code> before the input file.<br>
<p>Note: ffmpeg must be compiled with the tesseract library for this script to work (<code>--with-tesseract</code> if using the <code>brew install ffmpeg</code> method).</p>
<p>Note: FFmpeg must be compiled with the tesseract library for this script to work (<code>--with-tesseract</code> if using the <code>brew install ffmpeg</code> method)</p>
[The Cable Bible](https://amiaopensource.github.io/cable-bible/): A Guide to Cables and Connectors Used for Audiovisual Tech
[FFCommand_Engine](https://github.com/ColorlabMD/FFCommand_Engine): a tool for easier use of FFmpeg binaries
[QEMU QED](https://eaasi.gitlab.io/qemu-qed): instructions for using QEMU (Quick EMUlator), a command line application for computer emulation and virtualization
[QEMU QED](https://eaasi.gitlab.io/program_docs/qemu-qed/): instructions for using QEMU (Quick EMUlator), a command line application for computer emulation and virtualization
[Script Ahoy](http://dd388.github.io/crals/): Community Resource for Archivists and Librarians Scripting
[sourcecaster](https://datapraxis.github.io/sourcecaster/): helps you use the command line to work through common challenges that come up when working with digital primary sources.
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