From 750810d3924c76914c52b7f02c6b0eddc967c5a9 Mon Sep 17 00:00:00 2001
From: Andrew Weaver <weevz@uw.edu>
Date: Tue, 2 May 2017 19:58:20 -0700
Subject: [PATCH] Loudness/RIAA Curve (#179)

- start normalization section
- add RIAA
---
 index.html | 106 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)

diff --git a/index.html b/index.html
index 12edbad..f19e489 100644
--- a/index.html
+++ b/index.html
@@ -1081,6 +1081,112 @@
   <!-- ends append notice to access mp3 -->
 
   </div>
+
+  <div class="well">
+  <h4>Normalize/Equalize Audio</h4>
+
+  <!-- loudnorm metadata -->
+  <span data-toggle="modal" data-target="#loudnorm_metadata"><button type="button" class="btn btn-default" data-toggle="tooltip" data-placement="bottom" title="Calculate Loudness Levels">Calculate Loudness Levels</button></span>
+  <div id="loudnorm_metadata" class="modal fade" tabindex="-1" role="dialog">
+    <div class="modal-dialog modal-lg">
+      <div class="modal-content">
+        <div class="well">
+          <h3>Calculate Loudness Levels</h3>
+          <p><code>ffmpeg -i <i>input_file</i> -af loudnorm=print_format=json -f null -</code></p>
+          <p>This filter calculates and outputs loudness information in json about an input file (labeled input) as well as what the levels would be if loudnorm were applied in its one pass mode (labeled output). The values generated can be used as inputs for a 'second pass' of the loudnorm filter allowing more accurate loudness normalization than if it is used in a single pass.</p>
+          <p>These instructions use the loudnorm defaults, which align well with PBS recommendations for target loudness. More information can be found at the <a href=https://ffmpeg.org/ffmpeg-filters.html#loudnorm>loudnorm documentation</a>.</p>
+          <p>Information about PBS loudness standards can be found in the <a href=http://www-tc.pbs.org/capt/Producing/TOS-2012-Pt2-Distribution.pdf>PBS Technical Operating Specifications</a> document. Information about EBU loudness standards can be found in the <a href=https://tech.ebu.ch/docs/r/r128-2014.pdf>EBU R 128</a> recommendation document.</p>
+          <dl>
+            <dt>ffmpeg</dt><dd>starts the command</dd>
+            <dt><i>input_file</i></dt><dd>path, name and extension of the input file</dd>
+            <dt>-af loudnorm</dt><dd>activates the loudnorm filter</dd>
+            <dt>print_format=json</dt><dd>sets the output format for loudness information to json. This format makes it easy to use in a second pass. For a more human readable output, this can be set to <code>print_format=summary</code></dd>
+            <dt><i>-f null -</i></dt><dd>sets the file output to null (since we are only interested in the metadata generated)</dd>
+          </dl>
+          <p class="link"></p>
+        </div>
+      </div>
+    </div>
+  </div>
+  <!-- ends loudnorm metadata -->
+
+  <!-- one pass loudnorm -->
+  <span data-toggle="modal" data-target="#loudnorm_one_pass"><button type="button" class="btn btn-default" data-toggle="tooltip" data-placement="bottom" title="One Pass Loudness Normalization">One Pass Loudness Normalization</button></span>
+  <div id="loudnorm_one_pass" class="modal fade" tabindex="-1" role="dialog">
+    <div class="modal-dialog modal-lg">
+      <div class="modal-content">
+        <div class="well">
+          <h3>One Pass Loudness Normalization</h3>
+          <p><code>ffmpeg -i <i>input_file</i> -af loudnorm=dual_mono=true <i>output_file</i></code></p>
+          <p>This will normalize the loudness of an input using one pass, which is quicker but less accurate than using two passes. This command uses the loudnorm filter defaults for target loudness. These defaults align well with PBS recommendations, but loudnorm does allow targeting of specific loudness levels. More information can be found at the <a href=https://ffmpeg.org/ffmpeg-filters.html#loudnorm>loudnorm documentation</a>.</p>
+          <p>Information about PBS loudness standards can be found in the <a href=http://www-tc.pbs.org/capt/Producing/TOS-2012-Pt2-Distribution.pdf>PBS Technical Operating Specifications</a> document. Information about EBU loudness standards can be found in the <a href=https://tech.ebu.ch/docs/r/r128-2014.pdf>EBU R 128</a> recommendation document.</p>
+          <dl>
+            <dt>ffmpeg</dt><dd>starts the command</dd>
+            <dt><i>input_file</i></dt><dd>path, name and extension of the input file</dd>
+            <dt>-af loudnorm</dt><dd>activates the loudnorm filter with default settings</dd>
+            <dt>dual_mono=true</dt><dd>(optional) Use this for mono files meant to be played back on stereo systems for correct loudness. Not necessary for multi-track inputs.</dd>
+            <dt><i>output_file</i></dt><dd>path, name and extension for output file</dd>
+          </dl>
+          <p class="link"></p>
+        </div>
+      </div>
+    </div>
+  </div>
+  <!-- ends one pass loudnorm -->
+
+  <!-- two pass loudnorm -->
+  <span data-toggle="modal" data-target="#loudnorm_two_pass"><button type="button" class="btn btn-default" data-toggle="tooltip" data-placement="bottom" title="Two Pass Loudness Normalization">Two Pass Loudness Normalization</button></span>
+  <div id="loudnorm_two_pass" class="modal fade" tabindex="-1" role="dialog">
+    <div class="modal-dialog modal-lg">
+      <div class="modal-content">
+        <div class="well">
+          <h3>Two Pass Loudness Normalization</h3>
+          <p><code>ffmpeg -i <i>input_file</i> -af loudnorm=dual_mono=true:measured_I=<i>input_i</i>:measured_TP=<i>input_tp</i>:measured_LRA=<i>input_lra</i>:measured_thresh=<i>input_thresh</i>:offset=<i>target_offset</i>:linear=true <i>output_file</i></code></p>
+          <p>This command allows using the levels calculated using a <a href=#loudnorm_metadata>first pass of the loudnorm filter</a> to more accurately normalize loudness. This command uses the loudnorm filter defaults for target loudness. These defaults align well with PBS recommendations, but loudnorm does allow targeting of specific loudness levels. More information can be found at the <a href=https://ffmpeg.org/ffmpeg-filters.html#loudnorm>loudnorm documentation</a>.</p>
+          <p>Information about PBS loudness standards can be found in the <a href=http://www-tc.pbs.org/capt/Producing/TOS-2012-Pt2-Distribution.pdf>PBS Technical Operating Specifications</a> document. Information about EBU loudness standards can be found in the <a href=https://tech.ebu.ch/docs/r/r128-2014.pdf>EBU R 128</a> recommendation document.</p>
+          <dl>
+            <dt>ffmpeg</dt><dd>starts the command</dd>
+            <dt><i>input_file</i></dt><dd>path, name and extension of the input file</dd>
+            <dt>-af loudnorm</dt><dd>activates the loudnorm filter with default settings</dd>
+            <dt>dual_mono=true</dt><dd>(optional) use this for mono files meant to be played back on stereo systems for correct loudness. Not necessary for multi-track inputs.</dd>
+            <dt>measured_I=<i>input_i</i></dt><dd>use the 'input_i' value (integrated loudness) from the first pass in place of input_i</dd>
+            <dt>measured_TP=<i>input_tp</i></dt><dd>use the 'input_tp' value (true peak) from the first pass in place of input_tp</dd>
+            <dt>measured_LRA=<i>input_lra</i></dt><dd>use the 'input_lra' value (loudness range) from the first pass in place of input_lra</dd>
+            <dt>measured_LRA=<i>input_thresh</i></dt><dd>use the 'input_thresh' value (threshold) from the first pass in place of input_thresh</dd>
+            <dt>offset=<i>target_offset</i></dt><dd>use the 'target_offset' value (offset) from the first pass in place of target_offset</dd>
+            <dt>linear=true</i></dt><dd>tells loudnorm to use linear normalization</dd>
+            <dt><i>output_file</i></dt><dd>path, name and extension for output file</dd>
+          </dl>
+          <p class="link"></p>
+        </div>
+      </div>
+    </div>
+  </div>
+  <!-- ends two pass loudnorm -->
+
+  <!-- RIAA equalization -->
+  <span data-toggle="modal" data-target="#riaa_eq"><button type="button" class="btn btn-default" data-toggle="tooltip" data-placement="bottom" title="RIAA Equalization">RIAA Equalization</button></span>
+  <div id="riaa_eq" class="modal fade" tabindex="-1" role="dialog">
+    <div class="modal-dialog modal-lg">
+      <div class="modal-content">
+        <div class="well">
+          <h3>RIAA Equalization</h3>
+          <p><code>ffmpeg -i <i>input_file</i> -af aemphasis=type=riaa <i>output_file</i></code></p>
+          <p>This will apply RIAA equalization to an input file allowing correct listening of audio transferred 'flat' (without EQ) from records that used this EQ curve. For more information about RIAA equalization see the <a href=https://en.wikipedia.org/wiki/RIAA_equalization>Wikipedia page</a> on the subject.</p>
+          <dl>
+            <dt>ffmpeg</dt><dd>starts the command</dd>
+            <dt><i>input_file</i></dt><dd>path, name and extension of the input file</dd>
+            <dt>-af aemphasis=type=riaa</dt><dd>activates the aemphasis filter and sets it to use RIAA equalization</dd>
+            <dt><i>output_file</i></dt><dd>path and name of output file</dd>
+          </dl>
+          <p class="link"></p>
+        </div>
+      </div>
+    </div>
+  </div>
+  <!-- ends RIAA equalization -->
+  </div><!-- closes the well -->
+
   <div class="well">
   <h4>Preservation</h4>