New plugin which downmixes to stereo and applies DNC (#194)

* added downmix and DNC plugin

* removed unused functions and code. corrected link address

* renamed the file to match the correct shorthand. updated links and id too

* made adjustments to requirements for processing to only process files with 1 audio stream

* Lint fix

* Run checkPlugins and add recommended changes

Co-authored-by: HaveAGitGat <43864057+HaveAGitGat@users.noreply.github.com>

Community/Tdarr_Plugin_jeons001_Downmix_to_stereo_and_apply_DRC.js

@@ -0,0 +1,69 @@
+const loadDefaultValues = require('../methods/loadDefaultValues');
+
+const details = () => ({
+  id: 'Tdarr_Plugin_jeons001_Downmix_to_stereo_and_apply_DRC',
+  Stage: 'Pre-processing',
+  Name: 'Downmix & Dynamic range compression',
+  Type: 'Audio',
+  Operation: 'Transcode',
+  Description: 'Downmixes surround to AAC stereo AND applies dynamic range compression.'
+    + 'Files already in stereo or with multiple audio tracks will be skipped \n\n',
+  Version: '1.00',
+  Tags: 'ffmpeg',
+  Inputs: [],
+});
+
+// eslint-disable-next-line no-unused-vars
+const plugin = (file, librarySettings, inputs, otherArguments) => {
+  // eslint-disable-next-line no-unused-vars,no-param-reassign
+  inputs = loadDefaultValues(inputs, details);
+  const response = {
+    processFile: false,
+    preset: '',
+    handBrakeMode: false,
+    FFmpegMode: true,
+    reQueueAfter: true,
+    infoLog: '',
+    file,
+    removeFromDB: false,
+    updateDB: false,
+    container: `.${file.container}`,
+  };
+
+  let audioStreams = 0;
+  let surroundTrackFound = false;
+
+  for (let index = 0; index < file.ffProbeData.streams.length; index += 1) {
+    const stream = file.ffProbeData.streams[index];
+    if (stream.codec_type === 'audio') {
+      audioStreams += 1;
+    }
+
+    if (stream.codec_type === 'audio' && stream.channels && stream.channels > 3) {
+      surroundTrackFound = true;
+    }
+  }
+
+  if (audioStreams > 1) {
+    response.infoLog = 'File has more than 1 audio track - not processing';
+    return response;
+  }
+
+  if (!surroundTrackFound) {
+    response.infoLog = 'File has no surround tracks - not processing';
+    return response;
+  }
+
+  if (surroundTrackFound && audioStreams === 1) {
+    response.preset = '-sn <io> -vcodec copy -scodec copy -acodec aac -filter:a '
+    + '"dynaudnorm,pan=stereo|FL < 1.0*FL + 0.707*FC + 0.707*BL|FR < 1.0*FR + 0.707*FC + 0.707*BR"';
+    response.processFile = true;
+    response.infoLog = 'File matches requirements for processing. Downmixing and applying DRC!';
+    return response;
+  }
+
+  return response;
+};
+
+module.exports.details = details;
+module.exports.plugin = plugin;