Chunk playback proxy at 10MB and merge adaptive streams for saves

server/server.js

@@ -325,6 +325,9 @@ app.get('/api/channel', async (c) => {
 // videoId -> { info, formats:[{formatId,height,vcodec,acodec,abr,ext,url,headers}], expiresAt }
 const streamCache = new Map();
 const STREAM_CACHE_MAX = 200;
+// Max bytes per upstream googlevideo request (its adaptive streams are cut
+// after ~10 MB; matches yt-dlp's http_chunk_size).
+const PLAY_CHUNK = 10 * 1024 * 1024 - 1024;
 
 // googlevideo URLs carry `expire=<unix-seconds>`; return that as an ms epoch.
 function parseExpiry(url) {
@@ -535,7 +538,12 @@ app.get('/api/play', async (c) => {
     const fmt = pickFormat(formats, sel);
     if (!fmt) return { error: 'no matching format' };
     const headers = { ...fmt.headers };
-    if (range) headers['Range'] = range;
+    // Always ask upstream for a bounded slice (see PLAY_CHUNK below); the
+    // splicer extends it to the client's full requested range.
+    const rq = /bytes=(\d+)-(\d*)/.exec(range || '');
+    const from = rq ? Number(rq[1]) : 0;
+    const to = rq && rq[2] !== '' ? Math.min(Number(rq[2]), from + PLAY_CHUNK - 1) : from + PLAY_CHUNK - 1;
+    headers['Range'] = range && !rq ? range : `bytes=${from}-${to}`;
     return { fmt, res: await fetch(fmt.url, { headers, redirect: 'follow' }) };
   }
 
@@ -560,15 +568,77 @@ app.get('/api/play', async (c) => {
 
     const up = attempt.res;
     const headers = new Headers();
-    for (const k of ['content-type', 'content-length', 'content-range', 'accept-ranges']) {
+    headers.set('Content-Type', up.headers.get('content-type') || (sel.wantAudio ? 'audio/mp4' : 'video/mp4'));
-      const v = up.headers.get(k);
+    headers.set('Accept-Ranges', 'bytes');
-      if (v) headers.set(k, v);
-    }
-    if (!headers.has('accept-ranges')) headers.set('Accept-Ranges', 'bytes');
-    if (!headers.has('content-type')) headers.set('Content-Type', sel.wantAudio ? 'audio/mp4' : 'video/mp4');
     headers.set('Cache-Control', 'no-store');
 
-    return new Response(up.body, { status: up.status, headers });
+    // googlevideo silently closes adaptive-stream connections after ~10 MB
+    // (yt-dlp's own `http_chunk_size` exists for exactly this), so a single
+    // forwarded `bytes=0-` truncated at ~30 s of 720p and the <video> element
+    // stalled with no error. Re-issue upstream fetches in ≤10 MB Range slices
+    // and splice them into ONE response body that is byte-complete for the
+    // client's requested range.
+    const cr = /bytes (\d+)-(\d+)\/(\d+|\*)/.exec(up.headers.get('content-range') || '');
+    const total = cr && cr[3] !== '*' ? Number(cr[3])
+      : up.status === 200 ? Number(up.headers.get('content-length') || 0) : 0;
+    if (!total || up.status !== 206 && up.status !== 200) {
+      for (const k of ['content-length', 'content-range']) {
+        const v = up.headers.get(k);
+        if (v) headers.set(k, v);
+      }
+      return new Response(up.body, { status: up.status, headers });
+    }
+
+    const rq = /bytes=(\d*)-(\d*)/.exec(range || '');
+    let start = cr ? Number(cr[1]) : 0;
+    let end = total - 1;
+    if (rq && rq[2] !== '') end = Math.min(total - 1, Number(rq[2]));
+    if (rq && rq[1] === '' && rq[2] !== '') { start = Math.max(0, total - Number(rq[2])); end = total - 1; }
+    const length = end - start + 1;
+
+    const fmt = attempt.fmt;
+    const body = new ReadableStream({
+      async start(ctrl) {
+        // Upstream body is a slice already; the slice boundaries below are
+        // relative to `start`, and the first slice reuses the in-flight fetch.
+        let pos = start;
+        let res = up;
+        try {
+          while (pos <= end) {
+            const sliceEnd = Math.min(end, pos + PLAY_CHUNK - 1);
+            if (res === null) {
+              res = await fetch(fmt.url, { headers: { ...fmt.headers, Range: `bytes=${pos}-${sliceEnd}` }, redirect: 'follow' });
+              if (res.status !== 206 && res.status !== 200) throw new Error('upstream ' + res.status);
+            }
+            const reader = res.body.getReader();
+            let got = 0;
+            while (got < sliceEnd - pos + 1) {
+              const { value, done } = await reader.read();
+              if (done) break;
+              const room = sliceEnd - pos + 1 - got;
+              const chunk = value.length > room ? value.subarray(0, room) : value;
+              ctrl.enqueue(chunk);
+              got += chunk.length;
+            }
+            try { reader.cancel(); } catch {}
+            if (got === 0) throw new Error('upstream returned no bytes');
+            pos += got;
+            res = null;
+          }
+          ctrl.close();
+        } catch (err) {
+          ctrl.error(err);
+        }
+      },
+      cancel() { try { up.body?.cancel(); } catch {} },
+    });
+
+    headers.set('Content-Length', String(length));
+    if (range) {
+      headers.set('Content-Range', `bytes ${start}-${end}/${total}`);
+      return new Response(body, { status: 206, headers });
+    }
+    return new Response(body, { status: 200, headers });
   } catch (err) {
     return c.json({ ok: false, error: 'stream proxy failed: ' + err.message }, 502);
   }
@@ -715,11 +785,16 @@ app.get('/api/download/:videoId', async (c) => {
     }
   }
 
-  // Default save — best progressive (audio+video single-file) format, so no
+  // Default save — best progressive (audio+video single-file) format when
-  // ffmpeg is required anywhere in the chain.
+  // one exists, otherwise merge bestvideo (≤720p) + bestaudio with ffmpeg.
+  // YouTube now serves many videos with NO progressive format at all, which
+  // made the old progressive-only selector fail every save with
+  // "Requested format is not available".
   try {
     return await ytdlpDownloadResponse(videoId, fp, [
-      '-f', 'bestvideo[ext=mp4][acodec!=none]/bestvideo[acodec!=none]/best[ext=mp4]/best',
+      '-f', 'bestvideo[ext=mp4][acodec!=none]/bestvideo[acodec!=none]/best[ext=mp4][acodec!=none]/'
+          + 'bv*[height<=720][ext=mp4]+ba[ext=m4a]/bv*[height<=720]+ba/b',
+      '--merge-output-format', 'mp4',
     ]);
   } catch (err) {
     return c.json({ ok: false, error: err.message }, 500);