Fix audio formats on long videos getting throttled (#3870)

src/main/index.js

@@ -289,7 +289,7 @@ function runApp() {
     // InnerTube rejects requests if the referer isn't YouTube or empty
     const innertubeAndMediaRequestFilter = { urls: ['https://www.youtube.com/youtubei/*', 'https://*.googlevideo.com/videoplayback?*'] }
 
-    session.defaultSession.webRequest.onBeforeSendHeaders(innertubeAndMediaRequestFilter, ({ requestHeaders, url }, callback) => {
+    session.defaultSession.webRequest.onBeforeSendHeaders(innertubeAndMediaRequestFilter, ({ requestHeaders, url, resourceType }, callback) => {
       requestHeaders.Referer = 'https://www.youtube.com/'
       requestHeaders.Origin = 'https://www.youtube.com'
 
@@ -300,6 +300,38 @@ function runApp() {
         delete requestHeaders['Content-Type']
       }
 
+      // YouTube throttles the adaptive formats if you request a chunk larger than 10MiB.
+      // For the DASH formats we are fine as video.js doesn't seem to ever request chunks that big.
+      // The legacy formats don't have any chunk size limits.
+      // For the audio formats we need to handle it ourselves, as the browser requests the entire audio file,
+      // which means that for most videos that are loger than 10 mins, we get throttled, as the audio track file sizes surpass that 10MiB limit.
+
+      // This code checks if the file is larger than the limit, by checking the `clen` query param,
+      // which YouTube helpfully populates with the content length for us.
+      // If it does surpass that limit, it then checks if the requested range is larger than the limit
+      // (seeking right at the end of the video, would result in a small enough range to be under the chunk limit)
+      // if that surpasses the limit too, it then limits the requested range to 10MiB, by setting the range to `start-${start + 10MiB}`.
+      if (resourceType === 'media' && url.includes('&mime=audio') && requestHeaders.Range) {
+        const TEN_MIB = 10 * 1024 * 1024
+
+        const contentLength = parseInt(new URL(url).searchParams.get('clen'))
+
+        if (contentLength > TEN_MIB) {
+          const [startStr, endStr] = requestHeaders.Range.split('=')[1].split('-')
+
+          const start = parseInt(startStr)
+
+          // handle open ended ranges like `0-` and `1234-`
+          const end = endStr.length === 0 ? contentLength : parseInt(endStr)
+
+          if (end - start > TEN_MIB) {
+            const newEnd = start + TEN_MIB
+
+            requestHeaders.Range = `bytes=${start}-${newEnd}`
+          }
+        }
+      }
+
       // eslint-disable-next-line n/no-callback-literal
       callback({ requestHeaders })
     })