Do not transcode to an higher bitrate

Thanks bkil https://github.com/bkil

3 files changed, 43 insertions, 1 deletions

diff --git a/server/helpers/ffmpeg-utils.ts b/server/helpers/ffmpeg-utils.ts
index 1d610eff2..c8d6969ff 100644
--- a/server/helpers/ffmpeg-utils.ts
+++ b/server/helpers/ffmpeg-utils.ts
@@ -674,7 +674,12 @@ async function presetH264 (command: ffmpeg.FfmpegCommand, input: string, resolut
     // Constrained Encoding (VBV)
     // https://slhck.info/video/2017/03/01/rate-control.html
     // https://trac.ffmpeg.org/wiki/Limiting%20the%20output%20bitrate
-    const targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
+    let targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
+
+    // Don't transcode to an higher bitrate than the original file
+    const fileBitrate = await getVideoFileBitrate(input)
+    targetBitrate = Math.min(targetBitrate, fileBitrate)
+
     localCommand = localCommand.outputOptions([ `-maxrate ${targetBitrate}`, `-bufsize ${targetBitrate * 2}` ])
 
     // Keyframe interval of 2 seconds for faster seeking and resolution switching.
diff --git a/server/tests/api/videos/video-transcoder.ts b/server/tests/api/videos/video-transcoder.ts
index a1959e1a9..a3d7b8707 100644
--- a/server/tests/api/videos/video-transcoder.ts
+++ b/server/tests/api/videos/video-transcoder.ts
@@ -20,6 +20,7 @@ import {
   generateHighBitrateVideo,
   generateVideoWithFramerate,
   getMyVideos,
+  getServerFileSize,
   getVideo,
   getVideoFileMetadataUrl,
   getVideosList,
@@ -27,6 +28,7 @@ import {
   root,
   ServerInfo,
   setAccessTokensToServers,
+  updateCustomSubConfig,
   uploadVideo, uploadVideoAndGetId,
   waitJobs,
   webtorrentAdd
@@ -468,6 +470,41 @@ describe('Test video transcoding', function () {
     }
   })
 
+  it('Should not transcode to an higher bitrate than the original file', async function () {
+    this.timeout(160000)
+
+    const config = {
+      transcoding: {
+        enabled: true,
+        resolutions: {
+          '240p': true,
+          '360p': true,
+          '480p': true,
+          '720p': true,
+          '1080p': true
+        },
+        webtorrent: { enabled: true },
+        hls: { enabled: true }
+      }
+    }
+    await updateCustomSubConfig(servers[1].url, servers[1].accessToken, config)
+
+    const videoAttributes = {
+      name: 'low bitrate',
+      fixture: 'low-bitrate.mp4'
+    }
+
+    const resUpload = await uploadVideo(servers[1].url, servers[1].accessToken, videoAttributes)
+    const videoUUID = resUpload.body.video.uuid
+
+    await waitJobs(servers)
+
+    const resolutions = [ 240, 360, 480, 720, 1080 ]
+    for (const r of resolutions) {
+      expect(await getServerFileSize(servers[1], `videos/${videoUUID}-${r}.mp4`)).to.be.below(43)
+    }
+  })
+
   it('Should provide valid ffprobe data', async function () {
     this.timeout(160000)
 
diff --git a/server/tests/fixtures/low-bitrate.mp4 b/server/tests/fixtures/low-bitrate.mp4
new file mode 100644
index 000000000..69004eccc
--- /dev/null
+++ b/server/tests/fixtures/low-bitrate.mp4