Support encoding profiles

server/lib/video-transcoding-profiles.ts

@@ -0,0 +1,95 @@
+import { getTargetBitrate } from '../../shared/models/videos'
+import { AvailableEncoders, buildStreamSuffix, EncoderOptionsBuilder } from '../helpers/ffmpeg-utils'
+import { ffprobePromise, getAudioStream, getMaxAudioBitrate, getVideoFileBitrate, getVideoStreamFromFile } from '../helpers/ffprobe-utils'
+import { VIDEO_TRANSCODING_FPS } from '../initializers/constants'
+
+// ---------------------------------------------------------------------------
+// Available encoders profiles
+// ---------------------------------------------------------------------------
+
+// Resources:
+//  * https://slhck.info/video/2017/03/01/rate-control.html
+//  * https://trac.ffmpeg.org/wiki/Limiting%20the%20output%20bitrate
+
+const defaultX264VODOptionsBuilder: EncoderOptionsBuilder = async ({ input, resolution, fps }) => {
+  let targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
+
+  const probe = await ffprobePromise(input)
+
+  const videoStream = await getVideoStreamFromFile(input, probe)
+  if (!videoStream) {
+    return { outputOptions: [ ] }
+  }
+
+  // Don't transcode to an higher bitrate than the original file
+  const fileBitrate = await getVideoFileBitrate(input, probe)
+  targetBitrate = Math.min(targetBitrate, fileBitrate)
+
+  return {
+    outputOptions: [
+      `-maxrate ${targetBitrate}`, `-bufsize ${targetBitrate * 2}`
+    ]
+  }
+}
+
+const defaultX264LiveOptionsBuilder: EncoderOptionsBuilder = async ({ resolution, fps, streamNum }) => {
+  const targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
+
+  return {
+    outputOptions: [
+      `${buildStreamSuffix('-b:v', streamNum)} ${targetBitrate}`,
+      `-maxrate ${targetBitrate}`, `-bufsize ${targetBitrate * 2}`
+    ]
+  }
+}
+
+const defaultAACOptionsBuilder: EncoderOptionsBuilder = async ({ input, streamNum }) => {
+  const parsedAudio = await getAudioStream(input)
+
+  // We try to reduce the ceiling bitrate by making rough matches of bitrates
+  // Of course this is far from perfect, but it might save some space in the end
+
+  const audioCodecName = parsedAudio.audioStream['codec_name']
+
+  const bitrate = getMaxAudioBitrate(audioCodecName, parsedAudio.bitrate)
+
+  if (bitrate !== undefined && bitrate !== -1) {
+    return { outputOptions: [ buildStreamSuffix('-b:a', streamNum), bitrate + 'k' ] }
+  }
+
+  return { copy: true, outputOptions: [] }
+}
+
+const defaultLibFDKAACVODOptionsBuilder: EncoderOptionsBuilder = ({ streamNum }) => {
+  return { outputOptions: [ buildStreamSuffix('-q:a', streamNum), '5' ] }
+}
+
+const availableEncoders: AvailableEncoders = {
+  vod: {
+    libx264: {
+      default: defaultX264VODOptionsBuilder
+    },
+    aac: {
+      default: defaultAACOptionsBuilder
+    },
+    libfdk_aac: {
+      default: defaultLibFDKAACVODOptionsBuilder
+    }
+  },
+  live: {
+    libx264: {
+      default: defaultX264LiveOptionsBuilder
+    },
+    aac: {
+      default: defaultAACOptionsBuilder
+    }
+  }
+}
+
+// ---------------------------------------------------------------------------
+
+export {
+  availableEncoders
+}
+
+// ---------------------------------------------------------------------------