Add import and Export buttons to the Parametric Equalizer DSP (#800)

Feat: Add Support for import and export of the PEQ

This commit adds both import and export of the ParametricEQ DSP Filter
as Equalizer APO compatible files.

Since Equalizer Presets in APO's file format are widely adapted, this
also allows importing the user to import the EQ generated by REW or
similar software.

For now some advanced PEQ filter types are not supported.

Preamp is also not supported and set to 0dB.

src/components/dsp/DSPParametricEQ.vue

@@ -1,5 +1,26 @@
 <template>
   <v-container class="pa-2">
+    <!-- Import/Export Buttons to Load/Save Equalizer APO Settings -->
+    <div class="d-flex justify-end">
+      <v-btn variant="outlined" class="mr-2" @click="openApoFileImport">
+        <v-icon start>mdi-file-import</v-icon>
+        {{ $t("settings.dsp.parametric_eq.import_apo") }}
+      </v-btn>
+
+      <v-btn variant="outlined" class="mr-2" @click="exportApoSettings">
+        <v-icon start>mdi-file-export</v-icon>
+        {{ $t("settings.dsp.parametric_eq.export_apo") }}
+      </v-btn>
+
+      <input
+        ref="fileInputRef"
+        type="file"
+        accept=".txt"
+        class="d-none"
+        @change="handleApoUpload"
+      />
+    </div>
+
     <!-- Frequency Response Graph with Dark Theme Support -->
     <v-card elevation="0" color="transparent">
       <div ref="graphContainer" class="graph-container">
@@ -101,6 +122,117 @@ import DSPSlider from "./DSPSlider.vue";
 import { $t } from "@/plugins/i18n";
 import { useTheme } from "vuetify";
 
+const apoToBandType: Record<string, ParametricEQBandType> = {
+  PK: ParametricEQBandType.PEAK,
+  PEQ: ParametricEQBandType.PEAK,
+  HP: ParametricEQBandType.HIGH_PASS,
+  HPQ: ParametricEQBandType.HIGH_PASS,
+  LP: ParametricEQBandType.LOW_PASS,
+  LPQ: ParametricEQBandType.LOW_PASS,
+  LS: ParametricEQBandType.LOW_SHELF,
+  HS: ParametricEQBandType.HIGH_SHELF,
+  NO: ParametricEQBandType.NOTCH,
+  // Currently not supported are:
+  // Modal, BP, LSC x dB, HS x dB, AP, LS with dB slope, HS with dB slope
+  // and any other non Parametric EQ types
+};
+
+const bandTypeToApo: Record<ParametricEQBandType, string> = {
+  [ParametricEQBandType.PEAK]: "PK",
+  [ParametricEQBandType.HIGH_PASS]: "HP",
+  [ParametricEQBandType.LOW_PASS]: "LP",
+  [ParametricEQBandType.LOW_SHELF]: "LS",
+  [ParametricEQBandType.HIGH_SHELF]: "HS",
+  [ParametricEQBandType.NOTCH]: "NO",
+};
+
+const importApoSettings = (content: string) => {
+  const filters = [];
+  const lines = content.split("\n");
+  const bands: ParametricEQBand[] = [];
+
+  for (const line of lines) {
+    if (line.startsWith("Filter")) {
+      // Parses filter settings from REW or Equalizer APO text format.
+      // Syntax of APO (from https://sourceforge.net/p/equalizerapo/wiki/Configuration%20reference/):
+      // Filter <n>: ON <Type> Fc <Frequency> Hz Gain <Gain value> dB Q <Q value>
+      // Filter <n>: ON <Type> Fc <Frequency> Hz Gain <Gain value> dB BW Oct <Bandwidth value>
+      // Matches patterns like:
+      // - "Filter 1: ON PK Fc 29.15 Hz Gain -9.60 dB Q 1.007" (REW)
+      // - "Filter: ON PK 29.15 Hz -9.60 dB 1.007" (EQ APO)
+      const match = line.match(
+        /Filter(?:\s+\d+)?:\s+(ON|OFF)\s+(\w+)\s+(?:Fc\s+)?(\d+\.?\d*)\s*(?:Hz)?\s+(?:Gain\s+)?(-?\d+\.?\d*)\s+dB\s+(?:(?:Q\s+)?(\d+\.?\d*)|(?:BW\s+Oct\s+)(\d+\.?\d*))/,
+      );
+
+      if (match) {
+        const [_, enabled, type, frequency, gain, q, bw] = match;
+        // Convert BW to Q if BW is present
+        const finalQ = bw ? bandwidthToQ(parseFloat(bw)) : parseFloat(q);
+        if (type !== "None") {
+          bands.push({
+            frequency: parseFloat(frequency),
+            gain: parseFloat(gain),
+            q: parseFloat(q),
+            type: apoToBandType[type] || ParametricEQBandType.PEAK,
+            enabled: enabled === "ON",
+          });
+        }
+      }
+    }
+  }
+
+  // Update the PEQ bands
+  peq.value.bands = bands;
+  selectedBandIndex.value = 0;
+};
+
+// Helper function to convert bandwidth to Q factor
+function bandwidthToQ(bw: number): number {
+  // from https://sengpielaudio.com/calculator-bandwidth.htm
+  return Math.sqrt(Math.pow(2, bw)) / (Math.pow(2, bw) - 1);
+}
+
+const handleApoUpload = (event: Event) => {
+  const input = event.target as HTMLInputElement;
+  if (input.files && input.files[0]) {
+    const file = input.files[0];
+    const reader = new FileReader();
+
+    reader.onload = (e) => {
+      if (e.target?.result) {
+        importApoSettings(e.target.result as string);
+      }
+    };
+
+    reader.readAsText(file);
+  }
+};
+
+const fileInputRef = ref<HTMLInputElement | null>(null);
+
+const openApoFileImport = () => {
+  fileInputRef.value?.click();
+};
+
+const exportApoSettings = () => {
+  let content = "Preamp: 0 dB\n";
+
+  peq.value.bands.forEach((band) => {
+    const apoType = bandTypeToApo[band.type];
+    content += `Filter: ${band.enabled ? "ON" : "OFF"} ${apoType} Fc ${band.frequency.toFixed(1)} Hz Gain ${band.gain.toFixed(2)} dB Q ${band.q.toFixed(3)}\n`;
+  });
+  const blob = new Blob([content], { type: "text/plain" });
+  const url = URL.createObjectURL(blob);
+
+  const link = document.createElement("a");
+  link.href = url;
+  link.download = `music_assistant_eq_settings_${new Date().toISOString().split("T")[0]}.txt`;
+  document.body.appendChild(link);
+  link.click();
+  document.body.removeChild(link);
+  URL.revokeObjectURL(url);
+};
+
 const theme = useTheme();
 
 const peq = defineModel<ParametricEQFilter>({ required: true });

src/translations/en.json

@@ -449,6 +449,8 @@
                 "filter_type": "Filter Type",
                 "band": "Band {index}",
                 "enable_band": "Enable Band",
+                "import_apo": "Import APO/REW Preset",
+                "export_apo": "Export APO Preset",
                 "filter_types": {
                     "peak": "Peak",
                     "low_shelf": "Low Shelf",