.improve audio quality analyzer

backend/folder.go

@@ -50,12 +50,28 @@ func SelectFolderDialog(ctx context.Context, defaultPath string) (string, error)
 
 func SelectFileDialog(ctx context.Context) (string, error) {
 	options := wailsRuntime.OpenDialogOptions{
-		Title: "Select FLAC File for Analysis",
+		Title: "Select Audio File for Analysis",
 		Filters: []wailsRuntime.FileFilter{
+			{
+				DisplayName: "Audio Files (*.flac;*.mp3;*.m4a;*.aac)",
+				Pattern:     "*.flac;*.mp3;*.m4a;*.aac",
+			},
 			{
 				DisplayName: "FLAC Audio Files (*.flac)",
 				Pattern:     "*.flac",
 			},
+			{
+				DisplayName: "MP3 Audio Files (*.mp3)",
+				Pattern:     "*.mp3",
+			},
+			{
+				DisplayName: "M4A Audio Files (*.m4a)",
+				Pattern:     "*.m4a",
+			},
+			{
+				DisplayName: "AAC Audio Files (*.aac)",
+				Pattern:     "*.aac",
+			},
 			{
 				DisplayName: "All Files (*.*)",
 				Pattern:     "*.*",

frontend/src/components/AudioAnalysis.tsx

@@ -35,7 +35,7 @@ export function AudioAnalysis({ result, analyzing, onAnalyze, showAnalyzeButton
                         <div className="text-center space-y-2">
                             <p className="font-medium">Audio Quality Analysis</p>
                             <p className="text-sm text-muted-foreground">
-                                Verify the true lossless quality of downloaded files
+                                Inspect spectral content and effective quality of FLAC, MP3, M4A, and AAC files
                             </p>
                         </div>
                         {onAnalyze && (
@@ -73,6 +73,14 @@ export function AudioAnalysis({ result, analyzing, onAnalyze, showAnalyzeButton
     };
 
     const nyquistFreq = result.sample_rate / 2;
+    const totalSamplesText = result.total_samples > 0 ? result.total_samples.toLocaleString() : "N/A";
+    const freqResolutionLabel = result.file_type === "MP3" ? "Freq Res.:" : "Freq Resolution:";
+    const hasCodecMeta = result.file_type === "MP3" && (
+        Boolean(result.codec_mode) ||
+        typeof result.bitrate_kbps === "number" ||
+        typeof result.total_frames === "number" ||
+        Boolean(result.codec_version)
+    );
 
     return (
         <Card className="gap-2">
@@ -83,10 +91,16 @@ export function AudioAnalysis({ result, analyzing, onAnalyze, showAnalyzeButton
             </CardHeader>
 
             <CardContent>
-                <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-6">
+                <div className={`grid grid-cols-1 gap-6 md:grid-cols-2 ${hasCodecMeta ? "lg:grid-cols-4" : "lg:grid-cols-3"}`}>
                     <div className="space-y-2">
                         <p className="text-xs font-semibold tracking-wider text-muted-foreground uppercase">Format</p>
                         <ul className="text-sm space-y-1">
+                            {result.file_type && (
+                                <li className="flex justify-between">
+                                    <span className="text-muted-foreground">Type:</span>
+                                    <span className="font-medium font-mono">{result.file_type}</span>
+                                </li>
+                            )}
                             <li className="flex justify-between">
                                 <span className="text-muted-foreground">Sample Rate:</span>
                                 <span className="font-medium font-mono">{(result.sample_rate / 1000).toFixed(1)} kHz</span>
@@ -133,11 +147,43 @@ export function AudioAnalysis({ result, analyzing, onAnalyze, showAnalyzeButton
                             </li>
                             <li className="flex justify-between">
                                 <span className="text-muted-foreground">Total Samples:</span>
-                                <span className="font-medium font-mono">{result.total_samples.toLocaleString()}</span>
+                                <span className="font-medium font-mono">{totalSamplesText}</span>
                             </li>
                         </ul>
                     </div>
 
+                    {hasCodecMeta && (
+                        <div className="space-y-2">
+                            <p className="text-xs font-semibold tracking-wider text-muted-foreground uppercase">MP3 Meta</p>
+                            <ul className="text-sm space-y-1">
+                                {result.codec_mode && (
+                                    <li className="flex justify-between">
+                                        <span className="text-muted-foreground">Mode:</span>
+                                        <span className="font-medium font-mono">{result.codec_mode}</span>
+                                    </li>
+                                )}
+                                {typeof result.bitrate_kbps === "number" && (
+                                    <li className="flex justify-between">
+                                        <span className="text-muted-foreground">Bitrate:</span>
+                                        <span className="font-medium font-mono">{result.bitrate_kbps} kbps</span>
+                                    </li>
+                                )}
+                                {typeof result.total_frames === "number" && result.total_frames > 0 && (
+                                    <li className="flex justify-between">
+                                        <span className="text-muted-foreground">Frames:</span>
+                                        <span className="font-medium font-mono">{result.total_frames.toLocaleString()}</span>
+                                    </li>
+                                )}
+                                {result.codec_version && (
+                                    <li className="flex justify-between">
+                                        <span className="text-muted-foreground">Version:</span>
+                                        <span className="font-medium font-mono">{result.codec_version}</span>
+                                    </li>
+                                )}
+                            </ul>
+                        </div>
+                    )}
+
                     {result.spectrum && (() => {
                         const frames = result.spectrum.time_slices.length;
                         const fftSize = (result.spectrum.freq_bins - 1) * 2;
@@ -156,7 +202,7 @@ export function AudioAnalysis({ result, analyzing, onAnalyze, showAnalyzeButton
                                         <span className="font-medium font-mono">{fftSize.toLocaleString()}</span>
                                     </li>
                                     <li className="flex justify-between">
-                                        <span className="text-muted-foreground">Freq Resolution:</span>
+                                        <span className="text-muted-foreground">{freqResolutionLabel}</span>
                                         <span className="font-medium font-mono">{freqRes.toFixed(2)} Hz/bin</span>
                                     </li>
                                 </ul>

frontend/src/components/AudioAnalysisPage.tsx

@@ -13,16 +13,41 @@ interface AudioAnalysisPageProps {
     onBack?: () => void;
 }
 
-function isFlacPath(filePath: string): boolean {
+const SUPPORTED_AUDIO_EXTENSIONS = [".flac", ".mp3", ".m4a", ".aac"];
-    return filePath.toLowerCase().endsWith(".flac");
+const SUPPORTED_AUDIO_ACCEPT = [
+    ".flac",
+    ".mp3",
+    ".m4a",
+    ".aac",
+    "audio/flac",
+    "audio/x-flac",
+    "audio/mpeg",
+    "audio/mp3",
+    "audio/mp4",
+    "audio/x-m4a",
+    "audio/aac",
+    "audio/aacp",
+].join(",");
+const SUPPORTED_AUDIO_LABEL = "FLAC, MP3, M4A, or AAC";
+
+function isSupportedAudioPath(filePath: string): boolean {
+    const normalized = filePath.toLowerCase();
+    return SUPPORTED_AUDIO_EXTENSIONS.some((ext) => normalized.endsWith(ext));
 }
 
-function isFlacFile(file: File): boolean {
+function isSupportedAudioFile(file: File): boolean {
-    const name = file.name.toLowerCase();
+    const normalizedName = file.name.toLowerCase();
+    const normalizedType = file.type.toLowerCase();
     return (
-        name.endsWith(".flac") ||
+        SUPPORTED_AUDIO_EXTENSIONS.some((ext) => normalizedName.endsWith(ext)) ||
-        file.type === "audio/flac" ||
+        normalizedType === "audio/flac" ||
-        file.type === "audio/x-flac"
+        normalizedType === "audio/x-flac" ||
+        normalizedType === "audio/mpeg" ||
+        normalizedType === "audio/mp3" ||
+        normalizedType === "audio/mp4" ||
+        normalizedType === "audio/x-m4a" ||
+        normalizedType === "audio/aac" ||
+        normalizedType === "audio/aacp"
     );
 }
 
@@ -55,9 +80,9 @@ export function AudioAnalysisPage({ onBack }: AudioAnalysisPageProps) {
     const spectrumRef = useRef<{ getCanvasDataURL: () => string | null; }>(null);
 
     const analyzeSelectedPath = useCallback(async (filePath: string) => {
-        if (!isFlacPath(filePath)) {
+        if (!isSupportedAudioPath(filePath)) {
             toast.error("Invalid File Type", {
-                description: "Please select a FLAC file for analysis",
+                description: `Please select a ${SUPPORTED_AUDIO_LABEL} file for analysis`,
             });
             return;
         }
@@ -65,9 +90,9 @@ export function AudioAnalysisPage({ onBack }: AudioAnalysisPageProps) {
     }, [analyzeFilePath]);
 
     const analyzeSelectedFile = useCallback(async (file: File) => {
-        if (!isFlacFile(file)) {
+        if (!isSupportedAudioFile(file)) {
             toast.error("Invalid File Type", {
-                description: "Please select a FLAC file for analysis",
+                description: `Please select a ${SUPPORTED_AUDIO_LABEL} file for analysis`,
             });
             return;
         }
@@ -165,7 +190,7 @@ export function AudioAnalysisPage({ onBack }: AudioAnalysisPageProps) {
             <input
                 ref={fileInputRef}
                 type="file"
-                accept=".flac,audio/flac,audio/x-flac"
+                accept={SUPPORTED_AUDIO_ACCEPT}
                 className="hidden"
                 onChange={handleInputChange}
             />
@@ -221,13 +246,16 @@ export function AudioAnalysisPage({ onBack }: AudioAnalysisPageProps) {
                     </div>
                     <p className="text-sm text-muted-foreground mb-4 text-center">
                         {isDragging
-                            ? "Drop your FLAC file here"
+                            ? "Drop your audio file here"
-                            : "Drag and drop a FLAC file here, or click the button below to select"}
+                            : "Drag and drop an audio file here, or click the button below to select"}
                     </p>
                     <Button onClick={handleSelectFile} size="lg">
                         <Upload className="h-5 w-5" />
-                        Select FLAC File
+                        Select Audio File
                     </Button>
+                    <p className="text-xs text-muted-foreground mt-4 text-center">
+                        Supported formats: FLAC, MP3, M4A, AAC
+                    </p>
                 </div>
             )}
 

frontend/src/hooks/useAudioAnalysis.ts

@@ -3,8 +3,8 @@ import type { AnalysisResult } from "@/types/api";
 import { logger } from "@/lib/logger";
 import { toastWithSound as toast } from "@/lib/toast-with-sound";
 import {
-    analyzeFlacArrayBuffer,
+    analyzeAudioArrayBuffer,
-    analyzeFlacFile,
+    analyzeAudioFile,
     analyzeSpectrumFromSamples,
     type AnalysisProgress,
 } from "@/lib/flac-analysis";
@@ -159,7 +159,7 @@ export function useAudioAnalysis() {
             logger.info(`Analyzing audio file (frontend): ${file.name}`);
             const start = Date.now();
             const prefs = loadAudioAnalysisPreferences();
-            const payload = await analyzeFlacFile(file, {
+            const payload = await analyzeAudioFile(file, {
                 fftSize: prefs.fftSize,
                 windowFunction: prefs.windowFunction,
             }, (progress) => {
@@ -248,7 +248,7 @@ export function useAudioAnalysis() {
                 message: "Preparing audio buffer...",
             });
             const fileName = fileNameFromPath(filePath);
-            const payload = await analyzeFlacArrayBuffer(
+            const payload = await analyzeAudioArrayBuffer(
                 {
                     fileName,
                     fileSize: arrayBuffer.byteLength,

frontend/src/lib/flac-analysis.ts

@@ -12,13 +12,36 @@ const DEFAULT_PARAMS: SpectrumParams = {
 
 const MAX_SPECTRUM_FRAMES = 2200;
 const METRICS_CHUNK_SIZE = 262144;
+const AAC_SAMPLE_RATES = [
+    96000, 88200, 64000, 48000, 44100, 32000, 24000,
+    22050, 16000, 12000, 11025, 8000, 7350,
+] as const;
 
-interface FlacStreamInfo {
+const MP4_CONTAINER_TYPES = new Set([
+    "moov", "trak", "mdia", "minf", "stbl", "edts", "dinf",
+    "udta", "ilst", "meta", "stsd", "wave",
+]);
+
+type SupportedAudioFileType = "FLAC" | "MP3" | "M4A" | "AAC";
+
+interface ParsedAudioMetadata {
+    fileType: SupportedAudioFileType;
     sampleRate: number;
     channels: number;
     bitsPerSample: number;
     totalSamples: number;
     duration: number;
+    codecMode?: string;
+    bitrateKbps?: number;
+    totalFrames?: number;
+    codecVersion?: string;
+}
+
+interface Mp4BoxInfo {
+    offset: number;
+    size: number;
+    headerSize: number;
+    type: string;
 }
 
 export interface FrontendAnalysisPayload {
@@ -26,7 +49,7 @@ export interface FrontendAnalysisPayload {
     samples: Float32Array;
 }
 
-export interface FlacArrayBufferInput {
+export interface AudioArrayBufferInput {
     fileName: string;
     fileSize: number;
     arrayBuffer: ArrayBuffer;
@@ -50,10 +73,9 @@ function reportProgress(
     message: string,
 ): void {
     if (!callback) return;
-    const clamped = Math.max(0, Math.min(100, percent));
     callback({
         phase,
-        percent: clamped,
+        percent: Math.max(0, Math.min(100, percent)),
         message,
     });
 }
@@ -75,7 +97,66 @@ function nextTick(): Promise<void> {
     return new Promise((resolve) => setTimeout(resolve, 0));
 }
 
-function parseFlacStreamInfo(buffer: ArrayBuffer): FlacStreamInfo {
+function readFourCC(view: DataView, offset: number): string {
+    return String.fromCharCode(
+        view.getUint8(offset),
+        view.getUint8(offset + 1),
+        view.getUint8(offset + 2),
+        view.getUint8(offset + 3),
+    );
+}
+
+function fileExtension(fileName: string): string {
+    const normalized = fileName.toLowerCase();
+    const dotIndex = normalized.lastIndexOf(".");
+    return dotIndex >= 0 ? normalized.slice(dotIndex) : "";
+}
+
+function detectAudioFileType(buffer: ArrayBuffer, fileName = ""): SupportedAudioFileType {
+    const view = new DataView(buffer);
+
+    if (view.byteLength >= 4 && view.getUint32(0, false) === 0x664c6143) {
+        return "FLAC";
+    }
+
+    if (view.byteLength >= 3 &&
+        view.getUint8(0) === 0x49 &&
+        view.getUint8(1) === 0x44 &&
+        view.getUint8(2) === 0x33) {
+        return "MP3";
+    }
+
+    if (view.byteLength >= 8 && readFourCC(view, 4) === "ftyp") {
+        return "M4A";
+    }
+
+    if (view.byteLength >= 2 && view.getUint8(0) === 0xff && (view.getUint8(1) & 0xf6) === 0xf0) {
+        return "AAC";
+    }
+
+    for (let offset = 0; offset < Math.min(4096, view.byteLength - 4); offset++) {
+        const header = view.getUint32(offset, false);
+        if ((header >>> 21) === 0x7ff) {
+            const version = (header >>> 19) & 0x03;
+            const layer = (header >>> 17) & 0x03;
+            const sampleRateIndex = (header >>> 10) & 0x03;
+            if (version !== 1 && layer !== 0 && sampleRateIndex !== 3) {
+                return "MP3";
+            }
+        }
+    }
+
+    switch (fileExtension(fileName)) {
+        case ".flac": return "FLAC";
+        case ".mp3": return "MP3";
+        case ".m4a":
+        case ".mp4": return "M4A";
+        case ".aac": return "AAC";
+        default: throw new Error(`Unsupported audio format: ${fileName || "unknown"}`);
+    }
+}
+
+function parseFlacMetadata(buffer: ArrayBuffer): ParsedAudioMetadata {
     const data = new Uint8Array(buffer);
     if (data.length < 4 || data[0] !== 0x66 || data[1] !== 0x4c || data[2] !== 0x61 || data[3] !== 0x43) {
         throw new Error("Invalid FLAC file");
@@ -88,16 +169,11 @@ function parseFlacStreamInfo(buffer: ArrayBuffer): FlacStreamInfo {
         const blockLength = (data[offset + 1] << 16) | (data[offset + 2] << 8) | data[offset + 3];
         offset += 4;
 
-        if (offset + blockLength > data.length) {
+        if (offset + blockLength > data.length) break;
-            break;
-        }
 
         if (blockType === 0 && blockLength >= 18) {
             const streamInfo = data.subarray(offset, offset + blockLength);
-            const sampleRate =
+            const sampleRate = (streamInfo[10] << 12) | (streamInfo[11] << 4) | (streamInfo[12] >> 4);
-                (streamInfo[10] << 12) |
-                (streamInfo[11] << 4) |
-                (streamInfo[12] >> 4);
             const channels = ((streamInfo[12] >> 1) & 0x07) + 1;
             const bitsPerSample = (((streamInfo[12] & 0x01) << 4) | (streamInfo[13] >> 4)) + 1;
             const totalSamplesBig =
@@ -110,6 +186,7 @@ function parseFlacStreamInfo(buffer: ArrayBuffer): FlacStreamInfo {
             const duration = sampleRate > 0 && totalSamples > 0 ? totalSamples / sampleRate : 0;
 
             return {
+                fileType: "FLAC",
                 sampleRate,
                 channels,
                 bitsPerSample,
@@ -124,6 +201,344 @@ function parseFlacStreamInfo(buffer: ArrayBuffer): FlacStreamInfo {
     throw new Error("FLAC STREAMINFO metadata not found");
 }
 
+function skipId3v2Tag(view: DataView): number {
+    if (view.byteLength < 10 ||
+        view.getUint8(0) !== 0x49 ||
+        view.getUint8(1) !== 0x44 ||
+        view.getUint8(2) !== 0x33) {
+        return 0;
+    }
+
+    const size =
+        ((view.getUint8(6) & 0x7f) << 21) |
+        ((view.getUint8(7) & 0x7f) << 14) |
+        ((view.getUint8(8) & 0x7f) << 7) |
+        (view.getUint8(9) & 0x7f);
+
+    let offset = 10 + size;
+    if ((view.getUint8(5) & 0x10) !== 0) {
+        offset += 10;
+    }
+    return offset < view.byteLength ? offset : 0;
+}
+
+function getMp3Bitrate(version: number, layer: number, bitrateIndex: number): number {
+    const tables: Record<number, Record<number, number[]>> = {
+        1: {
+            1: [0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 0],
+            2: [0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0],
+            3: [0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0],
+        },
+        2: {
+            1: [0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0],
+            2: [0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0],
+            3: [0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0],
+        },
+    };
+
+    const normalizedVersion = version === 2.5 ? 2 : version;
+    return tables[normalizedVersion]?.[layer]?.[bitrateIndex] ?? 0;
+}
+
+function getMp3SamplesPerFrame(version: number, layer: number): number {
+    if (layer === 1) return 384;
+    if (version === 1) return 1152;
+    return 576;
+}
+
+interface Mp3FrameInfo {
+    version: number;
+    versionName: string;
+    layer: number;
+    sampleRate: number;
+    bitrate: number;
+    channels: number;
+    frameSize: number;
+    samplesPerFrame: number;
+}
+
+function parseMp3FrameHeader(header: number): Mp3FrameInfo | null {
+    if (((header >>> 21) & 0x7ff) !== 0x7ff) return null;
+
+    const versionBits = (header >>> 19) & 0x03;
+    const layerBits = (header >>> 17) & 0x03;
+    const bitrateIndex = (header >>> 12) & 0x0f;
+    const sampleRateIndex = (header >>> 10) & 0x03;
+    const padding = (header >>> 9) & 0x01;
+    const channelMode = (header >>> 6) & 0x03;
+
+    const versions = [2.5, null, 2, 1] as const;
+    const layers = [null, 3, 2, 1] as const;
+    const version = versions[versionBits];
+    const layer = layers[layerBits];
+    if (version === null || layer === null || sampleRateIndex === 3) return null;
+
+    const sampleRateTables: Record<1 | 2 | 25, [number, number, number]> = {
+        1: [44100, 48000, 32000],
+        2: [22050, 24000, 16000],
+        25: [11025, 12000, 8000],
+    };
+    const sampleRateKey = version === 2.5 ? 25 : (version as 1 | 2);
+    const sampleRate = sampleRateTables[sampleRateKey][sampleRateIndex];
+    const bitrate = getMp3Bitrate(version, layer, bitrateIndex);
+    const samplesPerFrame = getMp3SamplesPerFrame(version, layer);
+    if (!sampleRate || !bitrate || !samplesPerFrame) return null;
+
+    return {
+        version,
+        versionName: `MPEG-${version === 1 ? "1" : version === 2 ? "2" : "2.5"}`,
+        layer,
+        sampleRate,
+        bitrate,
+        channels: channelMode === 3 ? 1 : 2,
+        frameSize: Math.floor((samplesPerFrame / 8 * bitrate * 1000) / sampleRate) + padding,
+        samplesPerFrame,
+    };
+}
+
+function getMp3SideInfoSize(frameInfo: Mp3FrameInfo): number {
+    if (frameInfo.version === 1) {
+        return frameInfo.channels === 1 ? 17 : 32;
+    }
+    return frameInfo.channels === 1 ? 9 : 17;
+}
+
+function parseMp3XingHeader(view: DataView, offset: number, frameInfo: Mp3FrameInfo) {
+    if (offset + 16 > view.byteLength) return null;
+    const flags = view.getUint32(offset + 4, false);
+    let pos = offset + 8;
+    let totalFrames = 0;
+    let totalBytes = 0;
+
+    if ((flags & 0x01) !== 0 && pos + 4 <= view.byteLength) {
+        totalFrames = view.getUint32(pos, false);
+        pos += 4;
+    }
+    if ((flags & 0x02) !== 0 && pos + 4 <= view.byteLength) {
+        totalBytes = view.getUint32(pos, false);
+    }
+
+    const duration = totalFrames > 0 ? (totalFrames * frameInfo.samplesPerFrame) / frameInfo.sampleRate : 0;
+    const avgBitrate = duration > 0 && totalBytes > 0 ? Math.round((totalBytes * 8) / duration / 1000) : frameInfo.bitrate;
+
+    return {
+        codecMode: "VBR (Xing)",
+        totalFrames,
+        duration,
+        bitrateKbps: avgBitrate,
+    };
+}
+
+function parseMp3VbriHeader(view: DataView, offset: number, frameInfo: Mp3FrameInfo) {
+    if (offset + 18 > view.byteLength) return null;
+    const totalBytes = view.getUint32(offset + 10, false);
+    const totalFrames = view.getUint32(offset + 14, false);
+    const duration = totalFrames > 0 ? (totalFrames * frameInfo.samplesPerFrame) / frameInfo.sampleRate : 0;
+    const bitrateKbps = duration > 0 && totalBytes > 0 ? Math.round((totalBytes * 8) / duration / 1000) : frameInfo.bitrate;
+    return {
+        codecMode: "VBR (VBRI)",
+        totalFrames,
+        duration,
+        bitrateKbps,
+    };
+}
+
+function parseMp3VbrInfo(view: DataView, frameOffset: number, frameInfo: Mp3FrameInfo) {
+    const sideInfoSize = getMp3SideInfoSize(frameInfo);
+    const xingOffset = frameOffset + 4 + sideInfoSize;
+
+    if (xingOffset + 4 <= view.byteLength) {
+        const xingTag = String.fromCharCode(
+            view.getUint8(xingOffset),
+            view.getUint8(xingOffset + 1),
+            view.getUint8(xingOffset + 2),
+            view.getUint8(xingOffset + 3),
+        );
+        if (xingTag === "Xing" || xingTag === "Info") {
+            return parseMp3XingHeader(view, xingOffset, frameInfo);
+        }
+    }
+
+    const vbriOffset = frameOffset + 36;
+    if (vbriOffset + 4 <= view.byteLength) {
+        const vbriTag = String.fromCharCode(
+            view.getUint8(vbriOffset),
+            view.getUint8(vbriOffset + 1),
+            view.getUint8(vbriOffset + 2),
+            view.getUint8(vbriOffset + 3),
+        );
+        if (vbriTag === "VBRI") {
+            return parseMp3VbriHeader(view, vbriOffset, frameInfo);
+        }
+    }
+
+    return null;
+}
+
+function parseMp3Metadata(buffer: ArrayBuffer): ParsedAudioMetadata {
+    const view = new DataView(buffer);
+    const startOffset = skipId3v2Tag(view);
+
+    for (let offset = startOffset; offset <= view.byteLength - 4; offset++) {
+        const header = view.getUint32(offset, false);
+        const frameInfo = parseMp3FrameHeader(header);
+        if (frameInfo) {
+            const vbrInfo = parseMp3VbrInfo(view, offset, frameInfo);
+            const estimatedAudioDataSize = Math.max(0, view.byteLength - offset);
+            const estimatedFrameSize = frameInfo.frameSize > 0 ? frameInfo.frameSize : 1;
+            const totalFrames = vbrInfo?.totalFrames ?? Math.floor(estimatedAudioDataSize / estimatedFrameSize);
+            const duration = vbrInfo?.duration ?? ((totalFrames * frameInfo.samplesPerFrame) / frameInfo.sampleRate);
+            const bitrateKbps = vbrInfo?.bitrateKbps ?? frameInfo.bitrate;
+
+            return {
+                fileType: "MP3",
+                sampleRate: frameInfo.sampleRate,
+                channels: frameInfo.channels,
+                bitsPerSample: 16,
+                totalSamples: duration > 0 ? Math.floor(duration * frameInfo.sampleRate) : 0,
+                duration,
+                codecMode: vbrInfo?.codecMode ?? "CBR",
+                bitrateKbps,
+                totalFrames,
+                codecVersion: frameInfo.versionName,
+            };
+        }
+    }
+
+    throw new Error("No valid MP3 frame found");
+}
+
+function parseAacMetadata(buffer: ArrayBuffer): ParsedAudioMetadata {
+    const data = new Uint8Array(buffer);
+
+    for (let offset = 0; offset <= data.length - 7; offset++) {
+        if (data[offset] !== 0xff || (data[offset + 1] & 0xf6) !== 0xf0) continue;
+
+        const sampleRateIndex = (data[offset + 2] >> 2) & 0x0f;
+        const sampleRate = AAC_SAMPLE_RATES[sampleRateIndex];
+        const channels = ((data[offset + 2] & 0x01) << 2) | ((data[offset + 3] >> 6) & 0x03);
+        if (!sampleRate) continue;
+
+        return {
+            fileType: "AAC",
+            sampleRate,
+            channels: channels || 2,
+            bitsPerSample: 16,
+            totalSamples: 0,
+            duration: 0,
+        };
+    }
+
+    throw new Error("No valid AAC ADTS header found");
+}
+
+function readMp4Box(view: DataView, offset: number, limit: number): Mp4BoxInfo | null {
+    if (offset + 8 > limit) return null;
+
+    let size = view.getUint32(offset, false);
+    const type = readFourCC(view, offset + 4);
+    let headerSize = 8;
+
+    if (size === 1) {
+        if (offset + 16 > limit) return null;
+        const high = view.getUint32(offset + 8, false);
+        const low = view.getUint32(offset + 12, false);
+        size = high * 4294967296 + low;
+        headerSize = 16;
+    } else if (size === 0) {
+        size = limit - offset;
+    }
+
+    if (size < headerSize || offset + size > limit) return null;
+
+    return { offset, size, headerSize, type };
+}
+
+function parseM4aMetadata(buffer: ArrayBuffer): ParsedAudioMetadata {
+    const view = new DataView(buffer);
+    let sampleRate = 0;
+    let channels = 0;
+    let bitsPerSample = 0;
+    let duration = 0;
+
+    const scanBoxes = (start: number, end: number): void => {
+        let offset = start;
+        while (offset + 8 <= end) {
+            const box = readMp4Box(view, offset, end);
+            if (!box) break;
+
+            const boxEnd = box.offset + box.size;
+            const contentStart = box.offset + box.headerSize;
+
+            if (box.type === "mdhd" && contentStart + 24 <= boxEnd) {
+                const version = view.getUint8(contentStart);
+                if (version === 0 && contentStart + 24 <= boxEnd) {
+                    const timeScale = view.getUint32(contentStart + 12, false);
+                    const durationValue = view.getUint32(contentStart + 16, false);
+                    if (timeScale > 0) {
+                        sampleRate = timeScale;
+                        duration = durationValue / timeScale;
+                    }
+                } else if (version === 1 && contentStart + 36 <= boxEnd) {
+                    const timeScale = view.getUint32(contentStart + 20, false);
+                    const durationHigh = view.getUint32(contentStart + 24, false);
+                    const durationLow = view.getUint32(contentStart + 28, false);
+                    const durationValue = durationHigh * 4294967296 + durationLow;
+                    if (timeScale > 0) {
+                        sampleRate = timeScale;
+                        duration = durationValue / timeScale;
+                    }
+                }
+            } else if ((box.type === "mp4a" || box.type === "aac ") && box.offset + 36 <= boxEnd) {
+                channels = view.getUint16(box.offset + 24, false) || channels;
+                bitsPerSample = view.getUint16(box.offset + 26, false) || bitsPerSample;
+                if (!sampleRate) {
+                    const fixedPointSampleRate = view.getUint32(box.offset + 32, false);
+                    if (fixedPointSampleRate > 0) {
+                        sampleRate = Math.floor(fixedPointSampleRate / 65536);
+                    }
+                }
+            }
+
+            if (MP4_CONTAINER_TYPES.has(box.type)) {
+                let childStart = contentStart;
+                if (box.type === "meta") childStart = Math.min(boxEnd, contentStart + 4);
+                else if (box.type === "stsd") childStart = Math.min(boxEnd, contentStart + 8);
+                if (childStart < boxEnd) scanBoxes(childStart, boxEnd);
+            }
+
+            offset = boxEnd;
+        }
+    };
+
+    scanBoxes(0, view.byteLength);
+
+    if (sampleRate <= 0) sampleRate = 44100;
+    if (channels <= 0) channels = 2;
+    if (bitsPerSample <= 0) bitsPerSample = 16;
+
+    return {
+        fileType: "M4A",
+        sampleRate,
+        channels,
+        bitsPerSample,
+        totalSamples: duration > 0 ? Math.floor(duration * sampleRate) : 0,
+        duration,
+    };
+}
+
+function parseAudioMetadata(input: AudioArrayBufferInput): ParsedAudioMetadata {
+    const fileType = detectAudioFileType(input.arrayBuffer, input.fileName);
+
+    switch (fileType) {
+        case "FLAC": return parseFlacMetadata(input.arrayBuffer);
+        case "MP3": return parseMp3Metadata(input.arrayBuffer);
+        case "M4A": return parseM4aMetadata(input.arrayBuffer);
+        case "AAC": return parseAacMetadata(input.arrayBuffer);
+        default: throw new Error(`Unsupported audio format: ${input.fileName || "unknown"}`);
+    }
+}
+
 function buildWindowCoefficients(size: number, windowFunction: SpectrumParams["windowFunction"]): Float32Array {
     const coeffs = new Float32Array(size);
     if (size <= 1) {
@@ -309,7 +724,18 @@ export async function analyzeSpectrumFromSamples(
     };
 }
 
-export async function analyzeFlacFile(
+function createAnalysisAudioContext(sampleRate: number): AudioContext {
+    if (sampleRate > 0) {
+        try {
+            return new AudioContext({ sampleRate });
+        } catch {
+            return new AudioContext();
+        }
+    }
+    return new AudioContext();
+}
+
+export async function analyzeAudioFile(
     file: File,
     params: SpectrumParams = DEFAULT_PARAMS,
     onProgress?: AnalysisProgressCallback,
@@ -320,7 +746,7 @@ export async function analyzeFlacFile(
     const arrayBuffer = await file.arrayBuffer();
     throwIfCancelled(shouldCancel);
     reportProgress(onProgress, "read", 10, "File loaded");
-    return analyzeFlacArrayBuffer(
+    return analyzeAudioArrayBuffer(
         {
             fileName: file.name,
             fileSize: file.size,
@@ -335,18 +761,18 @@ export async function analyzeFlacFile(
     );
 }
 
-export async function analyzeFlacArrayBuffer(
+export async function analyzeAudioArrayBuffer(
-    input: FlacArrayBufferInput,
+    input: AudioArrayBufferInput,
     params: SpectrumParams = DEFAULT_PARAMS,
     onProgress?: AnalysisProgressCallback,
     shouldCancel?: AnalysisCancelCheck,
 ): Promise<FrontendAnalysisPayload> {
     throwIfCancelled(shouldCancel);
-    reportProgress(onProgress, "parse", 5, "Parsing FLAC metadata...");
+    reportProgress(onProgress, "parse", 5, "Parsing audio metadata...");
-    const streamInfo = parseFlacStreamInfo(input.arrayBuffer);
+    const metadata = parseAudioMetadata(input);
     throwIfCancelled(shouldCancel);
     reportProgress(onProgress, "decode", 15, "Decoding audio stream...");
-    const audioContext = new AudioContext({ sampleRate: streamInfo.sampleRate });
+    const audioContext = createAnalysisAudioContext(metadata.sampleRate);
 
     try {
         const audioBuffer = await audioContext.decodeAudioData(input.arrayBuffer.slice(0));
@@ -362,8 +788,7 @@ export async function analyzeFlacArrayBuffer(
             throwIfCancelled(shouldCancel);
             const sample = samples[i];
             const absSample = Math.abs(sample);
-            if (absSample > peak)
+            if (absSample > peak) peak = absSample;
-                peak = absSample;
             sumSquares += sample * sample;
 
             if ((i + 1) % METRICS_CHUNK_SIZE === 0 || i === samples.length - 1) {
@@ -383,11 +808,15 @@ export async function analyzeFlacArrayBuffer(
         const rms = samples.length > 0 ? Math.sqrt(sumSquares / samples.length) : 0;
         const rmsDB = rms > 0 ? 20 * Math.log10(rms) : -120;
         const dynamicRange = peakDB - rmsDB;
+        const duration = audioBuffer.duration > 0 ? audioBuffer.duration : metadata.duration;
+        const totalSamples = metadata.totalSamples > 0
+            ? metadata.totalSamples
+            : Math.floor(duration * metadata.sampleRate);
 
         reportProgress(onProgress, "metrics", 50, "Signal metrics complete");
         const spectrum = await analyzeSpectrumFromSamples(
             samples,
-            streamInfo.sampleRate,
+            metadata.sampleRate,
             params,
             (progress) => {
                 const mappedPercent = 50 + (progress.percent * 0.45);
@@ -395,9 +824,6 @@ export async function analyzeFlacArrayBuffer(
             },
             shouldCancel,
         );
-        const durationFromBuffer = audioBuffer.duration;
-        const duration = durationFromBuffer > 0 ? durationFromBuffer : streamInfo.duration;
-        const totalSamples = streamInfo.totalSamples > 0 ? streamInfo.totalSamples : Math.floor(duration * streamInfo.sampleRate);
 
         reportProgress(onProgress, "finalize", 97, "Finalizing result...");
 
@@ -405,15 +831,20 @@ export async function analyzeFlacArrayBuffer(
             result: {
                 file_path: input.fileName,
                 file_size: input.fileSize,
-                sample_rate: streamInfo.sampleRate,
+                file_type: metadata.fileType,
-                channels: streamInfo.channels,
+                sample_rate: metadata.sampleRate,
-                bits_per_sample: streamInfo.bitsPerSample,
+                channels: metadata.channels || audioBuffer.numberOfChannels,
+                bits_per_sample: metadata.bitsPerSample,
                 total_samples: totalSamples,
                 duration,
-                bit_depth: `${streamInfo.bitsPerSample}-bit`,
+                bit_depth: `${metadata.bitsPerSample}-bit`,
                 dynamic_range: dynamicRange,
                 peak_amplitude: peakDB,
                 rms_level: rmsDB,
+                codec_mode: metadata.codecMode,
+                bitrate_kbps: metadata.bitrateKbps,
+                total_frames: metadata.totalFrames,
+                codec_version: metadata.codecVersion,
                 spectrum,
             },
             samples,
@@ -425,3 +856,6 @@ export async function analyzeFlacArrayBuffer(
         await audioContext.close();
     }
 }
+
+export const analyzeFlacFile = analyzeAudioFile;
+export const analyzeFlacArrayBuffer = analyzeAudioArrayBuffer;

frontend/src/types/api.ts

@@ -167,6 +167,7 @@ export interface SpectrumData {
 export interface AnalysisResult {
     file_path: string;
     file_size: number;
+    file_type?: "FLAC" | "MP3" | "M4A" | "AAC";
     sample_rate: number;
     channels: number;
     bits_per_sample: number;
@@ -176,6 +177,10 @@ export interface AnalysisResult {
     dynamic_range: number;
     peak_amplitude: number;
     rms_level: number;
+    codec_mode?: string;
+    bitrate_kbps?: number;
+    total_frames?: number;
+    codec_version?: string;
     spectrum?: SpectrumData;
 }
 export interface LyricsDownloadRequest {