Add Video - Audio bitrate per channel

Adds option to change bitrate of audio streams based on a number of channel basis to preserve current mix where possible. Works similarly to the -vbr setting of libfdk_aac and similar options of other codecs. Includes fallback option for when channels are not available in stream's metadata. Also includes optional buffer to keep existing audio/settings if it is within a range of the original track

Scripts/Flow/Video/Video - Audio bitrate per channel.js

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+/**
+ * Sets the bitrate for audio streams based off the number of channels - in place of "Quality" options found on some audio codecs
+ * @author CanOfSocks
+ * @revision 1
+ * @param {int} Bitrate Desired bitrate per channel (default: 64000)
+ * @param {string} Codec Desired bitrate per channel (default: ac3)
+ * @param {int} Buffer Buffer above desired bitrate to not transcode (default: 0)
+ * @param {string} Channels Default mix/number of audio channels if not found (default: 2)
+ * @output Changes made to audio
+ * @output No changes made to audio
+ */
+function Script(Bitrate, Codec, Buffer, Channels){
+
+    //Sanatise inputs
+    let codec = "ac3"
+    if(Codec){
+        codec = `${Codec}`
+    }
+    let desiredBitrate = 64000;
+    if(Bitrate){
+        desiredBitrate = Number(Bitrate);
+    }
+    let acceptedDifference = 0;
+    if(Buffer){
+        acceptedDifference = Number(Buffer);
+    }
+    if(Channels && !isNaN(Channels)){   //Checks if channel is number mixdown e.g. 2, 5.1, 7.1 etc, sanatises if it is
+        Channels = Number(Channels);
+    } else if(Channels && /mono/i.test(`${Channels}`) === true){    //mono is only option that is not a default for a word input, refer to commented out section below for "stereo" implementation
+        Channels = 1;
+    } else {
+        Channels = 2;
+    }
+
+    /*  //Old implementation including stereo
+    }else if(Channels){     //in case input is "Stereo" or "Mono" - to match "Audio Converter" node inputs
+        if(/stereo/i.test(`${Channels}`) === true){
+            Channels = 2;
+        }else if(/mono/i.test(`${Channels}`) === true){
+            Channels = 1;
+        }else{  //fallback if neither
+            Channels = 2;
+        }
+    }else{      //if input isn't chosen or not valid, set to 2
+        Channels = 2;
+    }
+    */
+
+    let change = false; //assume no changes needed
+
+    for(let i=0;i<Variables?.FfmpegBuilderModel?.AudioStreams?.length;i++)
+    {
+        let builder = Variables.FfmpegBuilderModel.AudioStreams[i];
+        let as = Variables.vi?.VideoInfo?.AudioStreams[i];
+
+        if(builder.Deleted){    //ignore if already deleted
+            continue;
+        }
+        let currentBitrate = as.Bitrate;
+        if(currentBitrate === undefined) 
+            currentBitrate = 0;
+
+        //let channels = as.Channels;
+        let channels = Math.ceil(as.Channels*10)/10;    //rounds channels up to 1 dp - primarily for readability of logs
+
+        //If channels is 0, then no information is available, set to default. Assumes 0 if channels are less than mono (somehow)
+        if(channels === 0 || channels < 1){
+            channels = Channels;
+        }
+
+        //Full channels sets to ffmpeg equivalent channels for -ac, usually rounds up
+        let fullChannels = 2;
+        if(channels > 7){ 
+            fullChannels = 8;
+        } else if (channels > 5){
+            fullChannels = 6;
+        } else if(channels >=2){
+            fullChannels = 2;
+        } else if(channels >= 1){
+            fullChannels = 1;
+        } else {
+            fullChannels = 2;   //fall back to stereo in case no catch (somehow)
+        }
+
+
+        let perChannel = (currentBitrate/fullChannels)
+        let newBitrate = 0;
+        Logger.ILog(`Current total bitrate for audio track ${builder.Stream.TypeIndex}: ${currentBitrate}`);
+        Logger.ILog(`Current channels for audio track ${builder.Stream.TypeIndex}: ${channels}`);
+        Logger.ILog(`Current bitrate per channel for audio track ${builder.Stream.TypeIndex}: ${perChannel}`);
+
+        if((currentBitrate/fullChannels) >= (desiredBitrate+acceptedDifference) || (currentBitrate/fullChannels) === 0){
+            newBitrate = desiredBitrate * fullChannels;
+
+            Logger.ILog(`New total bitrate: ${newBitrate}`);
+            let params = [
+                /*"-c:a:{index}",*/ codec, //"-c:a:{index}" added automatically by builder
+                "-b:a:{index}", newBitrate,
+                "-ac:a:{index}", fullChannels
+            ];            
+
+            for (let j = 0; j < params.length; j++) {
+                builder.EncodingParameters.Add(params[j]);
+            }
+
+            change = true;
+        }
+
+    }
+    if(change){
+        return 1;
+    }else{
+        return 2;
+    }
+}