Fix transcoding errors in readonly docker containers

ffmpeg seems to create some temporary files in the cwd. When PeerTube
is run in a read-only docker container, this causes all transcoding
to fail. As a workaround, we set the cwd to the configured tmp dir.

package.json

@@ -166,7 +166,7 @@
     "@types/config": "^0.0.36",
     "@types/express": "^4.0.35",
     "@types/express-rate-limit": "^5.0.0",
-    "@types/fluent-ffmpeg": "^2.1.8",
+    "@types/fluent-ffmpeg": "2.1.14",
     "@types/fs-extra": "^9.0.1",
     "@types/libxmljs": "^0.18.0",
     "@types/lodash": "^4.14.64",

server/helpers/ffmpeg-utils.ts

@@ -270,7 +270,8 @@ type TranscodeOptions =
 function transcode (options: TranscodeOptions) {
   return new Promise<void>(async (res, rej) => {
     try {
-      let command = ffmpeg(options.inputPath, { niceness: FFMPEG_NICE.TRANSCODING })
+      // we set cwd explicitly because ffmpeg appears to create temporary files when trancoding which fails in read-only file systems
+      let command = ffmpeg(options.inputPath, { niceness: FFMPEG_NICE.TRANSCODING, cwd: CONFIG.STORAGE.TMP_DIR })
         .output(options.outputPath)
 
       if (options.type === 'quick-transcode') {

yarn.lock

@@ -591,7 +591,7 @@
     "@types/qs" "*"
     "@types/serve-static" "*"
 
-"@types/fluent-ffmpeg@^2.1.8":
+"@types/fluent-ffmpeg@2.1.14":
   version "2.1.14"
   resolved "https://registry.yarnpkg.com/@types/fluent-ffmpeg/-/fluent-ffmpeg-2.1.14.tgz#b21d60267fe269c2ea81fa3238a36a8349f8f2f3"
   integrity sha512-nJrAX9ODNI7mUB0b7Y0Stx1a6dOpV3zXsOnWoBuEd9/woQhepBNCMeCyOL6SLJD3jn5sLw5ciDGH0RwJenCoag==