Add DASH MPD parsing and MP4 to FLAC conversion functionality

src/helpers/utils.ts

@@ -2,6 +2,8 @@ import { FlacStreamTagger } from "flac-stream-tagger";
 import Ffmpeg from "fluent-ffmpeg";
 import ffmpegPath from "ffmpeg-static";
 import { PassThrough } from "stream";
+import { DashMPD } from '@liveinstantly/dash-mpd-parser';
+
 
 Ffmpeg.setFfmpegPath(ffmpegPath as string);
 
@@ -20,13 +22,33 @@ export default class {
 
         await new Promise((resolve, reject) => {
             Ffmpeg(inputStream)
-                .audioCodec("flac")
                 .format("flac")
                 .on("error", reject)
                 .on("end", resolve)
                 .pipe()
                 .on("data", chunk => outputChunks.push(chunk));
         });
+
+        return Buffer.concat(outputChunks);;
+    }
+
+    async convertMp4ToFlac(buffer: Buffer) {
+        const inputStream = new PassThrough();
+        inputStream.end(buffer);
+
+        const outputChunks: Buffer[] = [];
+
+        await new Promise((resolve, reject) => {
+            Ffmpeg(inputStream)
+                .audioCodec("flac")
+                .format("flac")
+                .on("error", reject)
+                .on("end", () => resolve(Buffer.concat(outputChunks)))
+                .pipe()
+                .on("data", chunk => outputChunks.push(chunk));
+        });
+
+        return Buffer.concat(outputChunks);
     }
 
     async fetchTrack(id: number) {
@@ -62,19 +84,30 @@ export default class {
     async downloadFlac(manifestMimeType: string, manifest: string) {
         const id = Bun.nanoseconds().toString(36);
         if (manifestMimeType === "application/dash+xml") {
-            await Bun.write(`tmp/${id}.mpd`, Buffer.from(manifest, "base64").toString("utf-8"))
+            const mpd = new DashMPD();
+            mpd.parse(Buffer.from(manifest, "base64").toString("utf-8"))
 
-            await Bun.$`${ffmpegPath} -protocol_whitelist https,file,tls,tcp -i tmp/${id}.mpd -c:a copy tmp/${id}.flac`.quiet()
+            const Representation = mpd.getJSON().MPD.Period[0].AdaptationSet[0].Representation[0];
+            const segmentTemplate = Representation.SegmentTemplate;
+            const segmentCount = segmentTemplate.SegmentTimeline.S[0]["@r"];
+            const segmentBuffers = [];
 
-            await Bun.file(`tmp/${id}.mpd`).delete();
+            const initialization = await fetch(segmentTemplate["@initialization"])
+            const initializationBuffer = await initialization.arrayBuffer()
+            segmentBuffers.push(Buffer.from(initializationBuffer));
 
-            const flac = Bun.file(`tmp/${id}.flac`)
+            const segmentPromises = [];
+            for (let i = 0; i < 1 + segmentCount; i++) {
+                const segmentUrl = segmentTemplate["@media"].replace("$Number$", segmentTemplate["@startNumber"] + i);
+                segmentPromises.push(fetch(segmentUrl).then(segment => segment.arrayBuffer()).then(segmentBuffer => Buffer.from(segmentBuffer)));
+            }
 
-            const audioBuffer = await flac.arrayBuffer();
+            const segmentBuffersArray = await Promise.all(segmentPromises);
+            segmentBuffers.push(...segmentBuffersArray);
 
-            await flac.delete()
+            const flac = await this.convertMp4ToFlac(Buffer.concat(segmentBuffers))
 
-            return { buffer: audioBuffer, mimeType: "audio/flac" }
+            return { buffer: flac, mimeType: "audio/flac" }
         } else if (manifestMimeType === "application/vnd.tidal.bts") {
             const data = JSON.parse(Buffer.from(manifest, "base64").toString("utf-8")) as {
                 "mimeType": string,