2 files changed, 135 insertions, 0 deletions

diff --git a/shared/ffmpeg/ffmpeg-default-transcoding-profile.ts b/shared/ffmpeg/ffmpeg-default-transcoding-profile.ts
new file mode 100644
index 000000000..f7fc49465
--- /dev/null
+++ b/shared/ffmpeg/ffmpeg-default-transcoding-profile.ts
@@ -0,0 +1,134 @@
+import { getAverageBitrate, getMinLimitBitrate } from '@shared/core-utils'
+import { buildStreamSuffix, ffprobePromise, getAudioStream, getMaxAudioBitrate } from '@shared/ffmpeg'
+import { EncoderOptionsBuilder, EncoderOptionsBuilderParams, VideoResolution } from '@shared/models'
+
+const defaultX264VODOptionsBuilder: EncoderOptionsBuilder = (options: EncoderOptionsBuilderParams) => {
+  const { fps, inputRatio, inputBitrate, resolution } = options
+
+  const targetBitrate = getTargetBitrate({ inputBitrate, ratio: inputRatio, fps, resolution })
+
+  return {
+    outputOptions: [
+      ...getCommonOutputOptions(targetBitrate),
+
+      `-r ${fps}`
+    ]
+  }
+}
+
+const defaultX264LiveOptionsBuilder: EncoderOptionsBuilder = (options: EncoderOptionsBuilderParams) => {
+  const { streamNum, fps, inputBitrate, inputRatio, resolution } = options
+
+  const targetBitrate = getTargetBitrate({ inputBitrate, ratio: inputRatio, fps, resolution })
+
+  return {
+    outputOptions: [
+      ...getCommonOutputOptions(targetBitrate, streamNum),
+
+      `${buildStreamSuffix('-r:v', streamNum)} ${fps}`,
+      `${buildStreamSuffix('-b:v', streamNum)} ${targetBitrate}`
+    ]
+  }
+}
+
+const defaultAACOptionsBuilder: EncoderOptionsBuilder = async ({ input, streamNum, canCopyAudio }) => {
+  const probe = await ffprobePromise(input)
+
+  const parsedAudio = await getAudioStream(input, probe)
+
+  // 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)
+
+  // Force stereo as it causes some issues with HLS playback in Chrome
+  const base = [ '-channel_layout', 'stereo' ]
+
+  if (bitrate !== -1) {
+    return { outputOptions: base.concat([ buildStreamSuffix('-b:a', streamNum), bitrate + 'k' ]) }
+  }
+
+  return { outputOptions: base }
+}
+
+const defaultLibFDKAACVODOptionsBuilder: EncoderOptionsBuilder = ({ streamNum }) => {
+  return { outputOptions: [ buildStreamSuffix('-q:a', streamNum), '5' ] }
+}
+
+export function getDefaultAvailableEncoders () {
+  return {
+    vod: {
+      libx264: {
+        default: defaultX264VODOptionsBuilder
+      },
+      aac: {
+        default: defaultAACOptionsBuilder
+      },
+      libfdk_aac: {
+        default: defaultLibFDKAACVODOptionsBuilder
+      }
+    },
+    live: {
+      libx264: {
+        default: defaultX264LiveOptionsBuilder
+      },
+      aac: {
+        default: defaultAACOptionsBuilder
+      }
+    }
+  }
+}
+
+export function getDefaultEncodersToTry () {
+  return {
+    vod: {
+      video: [ 'libx264' ],
+      audio: [ 'libfdk_aac', 'aac' ]
+    },
+
+    live: {
+      video: [ 'libx264' ],
+      audio: [ 'libfdk_aac', 'aac' ]
+    }
+  }
+}
+
+// ---------------------------------------------------------------------------
+
+function getTargetBitrate (options: {
+  inputBitrate: number
+  resolution: VideoResolution
+  ratio: number
+  fps: number
+}) {
+  const { inputBitrate, resolution, ratio, fps } = options
+
+  const capped = capBitrate(inputBitrate, getAverageBitrate({ resolution, fps, ratio }))
+  const limit = getMinLimitBitrate({ resolution, fps, ratio })
+
+  return Math.max(limit, capped)
+}
+
+function capBitrate (inputBitrate: number, targetBitrate: number) {
+  if (!inputBitrate) return targetBitrate
+
+  // Add 30% margin to input bitrate
+  const inputBitrateWithMargin = inputBitrate + (inputBitrate * 0.3)
+
+  return Math.min(targetBitrate, inputBitrateWithMargin)
+}
+
+function getCommonOutputOptions (targetBitrate: number, streamNum?: number) {
+  return [
+    `-preset veryfast`,
+    `${buildStreamSuffix('-maxrate:v', streamNum)} ${targetBitrate}`,
+    `${buildStreamSuffix('-bufsize:v', streamNum)} ${targetBitrate * 2}`,
+
+    // NOTE: b-strategy 1 - heuristic algorithm, 16 is optimal B-frames for it
+    `-b_strategy 1`,
+    // NOTE: Why 16: https://github.com/Chocobozzz/PeerTube/pull/774. b-strategy 2 -> B-frames<16
+    `-bf 16`
+  ]
+}
diff --git a/shared/ffmpeg/index.ts b/shared/ffmpeg/index.ts
index 07a7d5402..1dab292da 100644
--- a/shared/ffmpeg/index.ts
+++ b/shared/ffmpeg/index.ts
@@ -1,4 +1,5 @@
 export * from './ffmpeg-command-wrapper'
+export * from './ffmpeg-default-transcoding-profile'
 export * from './ffmpeg-edition'
 export * from './ffmpeg-images'
 export * from './ffmpeg-live'