server/lib/video-transcoding-profiles.ts

   1 import { getTargetBitrate } from '../../shared/models/videos'
   2 import { AvailableEncoders, buildStreamSuffix, EncoderOptionsBuilder } from '../helpers/ffmpeg-utils'
   3 import { ffprobePromise, getAudioStream, getMaxAudioBitrate, getVideoFileBitrate, getVideoStreamFromFile } from '../helpers/ffprobe-utils'
   4 import { VIDEO_TRANSCODING_FPS } from '../initializers/constants'
   5
   6 // ---------------------------------------------------------------------------
   7 // Available encoders profiles
   8 // ---------------------------------------------------------------------------
   9
  10 // Resources:
  11 //  * https://slhck.info/video/2017/03/01/rate-control.html
  12 //  * https://trac.ffmpeg.org/wiki/Limiting%20the%20output%20bitrate
  13
  14 const defaultX264VODOptionsBuilder: EncoderOptionsBuilder = async ({ input, resolution, fps }) => {
  15   let targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
  16
  17   const probe = await ffprobePromise(input)
  18
  19   const videoStream = await getVideoStreamFromFile(input, probe)
  20   if (!videoStream) {
  21     return { outputOptions: [ ] }
  22   }
  23
  24   // Don't transcode to an higher bitrate than the original file
  25   const fileBitrate = await getVideoFileBitrate(input, probe)
  26   targetBitrate = Math.min(targetBitrate, fileBitrate)
  27
  28   return {
  29     outputOptions: [
  30       `-maxrate ${targetBitrate}`, `-bufsize ${targetBitrate * 2}`
  31     ]
  32   }
  33 }
  34
  35 const defaultX264LiveOptionsBuilder: EncoderOptionsBuilder = async ({ resolution, fps, streamNum }) => {
  36   const targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
  37
  38   return {
  39     outputOptions: [
  40       `${buildStreamSuffix('-b:v', streamNum)} ${targetBitrate}`,
  41       `-maxrate ${targetBitrate}`, `-bufsize ${targetBitrate * 2}`
  42     ]
  43   }
  44 }
  45
  46 const defaultAACOptionsBuilder: EncoderOptionsBuilder = async ({ input, streamNum }) => {
  47   const parsedAudio = await getAudioStream(input)
  48
  49   // We try to reduce the ceiling bitrate by making rough matches of bitrates
  50   // Of course this is far from perfect, but it might save some space in the end
  51
  52   const audioCodecName = parsedAudio.audioStream['codec_name']
  53
  54   const bitrate = getMaxAudioBitrate(audioCodecName, parsedAudio.bitrate)
  55
  56   if (bitrate !== undefined && bitrate !== -1) {
  57     return { outputOptions: [ buildStreamSuffix('-b:a', streamNum), bitrate + 'k' ] }
  58   }
  59
  60   return { copy: true, outputOptions: [] }
  61 }
  62
  63 const defaultLibFDKAACVODOptionsBuilder: EncoderOptionsBuilder = ({ streamNum }) => {
  64   return { outputOptions: [ buildStreamSuffix('-q:a', streamNum), '5' ] }
  65 }
  66
  67 const availableEncoders: AvailableEncoders = {
  68   vod: {
  69     libx264: {
  70       default: defaultX264VODOptionsBuilder
  71     },
  72     aac: {
  73       default: defaultAACOptionsBuilder
  74     },
  75     libfdk_aac: {
  76       default: defaultLibFDKAACVODOptionsBuilder
  77     }
  78   },
  79   live: {
  80     libx264: {
  81       default: defaultX264LiveOptionsBuilder
  82     },
  83     aac: {
  84       default: defaultAACOptionsBuilder
  85     }
  86   }
  87 }
  88
  89 // ---------------------------------------------------------------------------
  90
  91 export {
  92   availableEncoders
  93 }
  94
  95 // ---------------------------------------------------------------------------