api: initial subtitles functionality with youtube support

this took way more effort than i expected it to do, mostly because of youtube locking everything down to shit

local processing doesn't function with subtitles yet, wasm needs to be updated

api/src/stream/manage.js

@@ -41,7 +41,10 @@ export function createStream(obj) {
             audioFormat: obj.audioFormat,
 
             isHLS: obj.isHLS || false,
-            originalRequest: obj.originalRequest
+            originalRequest: obj.originalRequest,
+
+            // url to a subtitle file
+            subtitles: obj.subtitles,
         };
 
     // FIXME: this is now a Promise, but it is not awaited
@@ -94,6 +97,18 @@ export function createProxyTunnels(info) {
         );
     }
 
+    if (info.subtitles) {
+        proxyTunnels.push(
+            createStream({
+                url: info.subtitles,
+                type: "proxy",
+                service: `${info?.service}-subtitles`,
+                headers: info?.headers,
+                requestIP: info?.requestIP
+            })
+        );
+    }
+
     return proxyTunnels;
 }
 
@@ -111,7 +126,7 @@ export function getInternalTunnelFromURL(url) {
     return getInternalTunnel(id);
 }
 
-export function createInternalStream(url, obj = {}) {
+export function createInternalStream(url, obj = {}, isSubtitles) {
     assert(typeof url === 'string');
 
     let dispatcher = obj.dispatcher;
@@ -132,9 +147,12 @@ export function createInternalStream(url, obj = {}) {
         headers = new Map(Object.entries(obj.headers));
     }
 
+    // subtitles don't need special treatment unlike big media files
+    const service = isSubtitles ? `${obj.service}-subtitles` : obj.service;
+
     internalStreamCache.set(streamID, {
         url,
-        service: obj.service,
+        service,
         headers,
         controller,
         dispatcher,
@@ -245,6 +263,14 @@ function wrapStream(streamInfo) {
         }
     } else throw 'invalid urls';
 
+    if (streamInfo.subtitles) {
+        streamInfo.subtitles = createInternalStream(
+            streamInfo.subtitles,
+            streamInfo,
+            /*isSubtitles=*/true
+        );
+    }
+
     return streamInfo;
 }
 

api/src/stream/types.js

@@ -25,6 +25,7 @@ const metadataTags = [
     "album_artist",
     "track",
     "date",
+    "sublanguage"
 ];
 
 const convertMetadataToFFmpeg = (metadata) => {
@@ -32,6 +33,10 @@ const convertMetadataToFFmpeg = (metadata) => {
 
     for (const [ name, value ] of Object.entries(metadata)) {
         if (metadataTags.includes(name)) {
+            if (name === "sublanguage") {
+                args.push('-metadata:s:s:0', `language=${value}`);
+                continue;
+            }
             args.push('-metadata', `${name}=${value.replace(/[\u0000-\u0009]/g, "")}`); // skipcq: JS-0004
         } else {
             throw `${name} metadata tag is not supported.`;
@@ -109,9 +114,6 @@ const merge = async (streamInfo, res) => {
         streamInfo.urls.map(destroyInternalStream)
     );
 
-    const headers = getHeaders(streamInfo.service);
-    const rawHeaders = toRawHeaders(headers);
-
     try {
         if (streamInfo.urls.length !== 2) return shutdown();
 
@@ -119,13 +121,21 @@ const merge = async (streamInfo, res) => {
 
         let args = [
             '-loglevel', '-8',
-            '-headers', rawHeaders,
             '-i', streamInfo.urls[0],
-            '-headers', rawHeaders,
             '-i', streamInfo.urls[1],
+        ];
+
+        if (streamInfo.subtitles) {
+            args.push(
+                '-i', streamInfo.subtitles,
+                '-map', '2:s'
+            );
+        };
+
+        args.push(
             '-map', '0:v',
             '-map', '1:a',
-        ]
+        );
 
         args = args.concat(ffmpegArgs[format]);
 
@@ -137,8 +147,12 @@ const merge = async (streamInfo, res) => {
             }
         }
 
+        if (streamInfo.subtitles && format === "mp4") {
+            args.push('-c:s', 'mov_text');
+        }
+
         if (streamInfo.metadata) {
-            args = args.concat(convertMetadataToFFmpeg(streamInfo.metadata))
+            args = args.concat(convertMetadataToFFmpeg(streamInfo.metadata));
         }
 
         args.push('-f', format, 'pipe:3');