server/lib/video-transcoding-profiles.ts

   1 import { logger } from '@server/helpers/logger'
   2 import { getTargetBitrate, VideoResolution } from '../../shared/models/videos'
   3 import { AvailableEncoders, buildStreamSuffix, EncoderOptionsBuilder } from '../helpers/ffmpeg-utils'
   4 import {
   5   canDoQuickAudioTranscode,
   6   ffprobePromise,
   7   getAudioStream,
   8   getMaxAudioBitrate,
   9   getVideoFileBitrate,
  10   getVideoStreamFromFile
  11 } from '../helpers/ffprobe-utils'
  12 import { VIDEO_TRANSCODING_FPS } from '../initializers/constants'
  13
  14 /**
  15  *
  16  * Available encoders and profiles for the transcoding jobs
  17  * These functions are used by ffmpeg-utils that will get the encoders and options depending on the chosen profile
  18  *
  19  */
  20
  21 // Resources:
  22 //  * https://slhck.info/video/2017/03/01/rate-control.html
  23 //  * https://trac.ffmpeg.org/wiki/Limiting%20the%20output%20bitrate
  24
  25 const defaultX264VODOptionsBuilder: EncoderOptionsBuilder = async ({ input, resolution, fps }) => {
  26   const targetBitrate = await buildTargetBitrate({ input, resolution, fps })
  27   if (!targetBitrate) return { outputOptions: [ ] }
  28
  29   return {
  30     outputOptions: [
  31       `-r ${fps}`,
  32       `-maxrate ${targetBitrate}`,
  33       `-bufsize ${targetBitrate * 2}`
  34     ]
  35   }
  36 }
  37
  38 const defaultX264LiveOptionsBuilder: EncoderOptionsBuilder = async ({ resolution, fps, streamNum }) => {
  39   const targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
  40
  41   return {
  42     outputOptions: [
  43       `${buildStreamSuffix('-r:v', streamNum)} ${fps}`,
  44       `${buildStreamSuffix('-b:v', streamNum)} ${targetBitrate}`,
  45       `-maxrate ${targetBitrate}`,
  46       `-bufsize ${targetBitrate * 2}`
  47     ]
  48   }
  49 }
  50
  51 const defaultAACOptionsBuilder: EncoderOptionsBuilder = async ({ input, streamNum }) => {
  52   const probe = await ffprobePromise(input)
  53
  54   if (await canDoQuickAudioTranscode(input, probe)) {
  55     logger.debug('Copy audio stream %s by AAC encoder.', input)
  56     return { copy: true, outputOptions: [] }
  57   }
  58
  59   const parsedAudio = await getAudioStream(input, probe)
  60
  61   // We try to reduce the ceiling bitrate by making rough matches of bitrates
  62   // Of course this is far from perfect, but it might save some space in the end
  63
  64   const audioCodecName = parsedAudio.audioStream['codec_name']
  65
  66   const bitrate = getMaxAudioBitrate(audioCodecName, parsedAudio.bitrate)
  67
  68   logger.debug('Calculating audio bitrate of %s by AAC encoder.', input, { bitrate: parsedAudio.bitrate, audioCodecName })
  69
  70   if (bitrate !== undefined && bitrate !== -1) {
  71     return { outputOptions: [ buildStreamSuffix('-b:a', streamNum), bitrate + 'k' ] }
  72   }
  73
  74   return { outputOptions: [ ] }
  75 }
  76
  77 const defaultLibFDKAACVODOptionsBuilder: EncoderOptionsBuilder = ({ streamNum }) => {
  78   return { outputOptions: [ buildStreamSuffix('-q:a', streamNum), '5' ] }
  79 }
  80
  81 // Used to get and update available encoders
  82 class VideoTranscodingProfilesManager {
  83   private static instance: VideoTranscodingProfilesManager
  84
  85   // 1 === less priority
  86   private readonly encodersPriorities = {
  87     video: [
  88       { name: 'libx264', priority: 100 }
  89     ],
  90
  91     // Try the first one, if not available try the second one etc
  92     audio: [
  93       // we favor VBR, if a good AAC encoder is available
  94       { name: 'libfdk_aac', priority: 200 },
  95       { name: 'aac', priority: 100 }
  96     ]
  97   }
  98
  99   private readonly availableEncoders = {
 100     vod: {
 101       libx264: {
 102         default: defaultX264VODOptionsBuilder
 103       },
 104       aac: {
 105         default: defaultAACOptionsBuilder
 106       },
 107       libfdk_aac: {
 108         default: defaultLibFDKAACVODOptionsBuilder
 109       }
 110     },
 111     live: {
 112       libx264: {
 113         default: defaultX264LiveOptionsBuilder
 114       },
 115       aac: {
 116         default: defaultAACOptionsBuilder
 117       }
 118     }
 119   }
 120
 121   private constructor () {
 122
 123   }
 124
 125   getAvailableEncoders (): AvailableEncoders {
 126     const encodersToTry = {
 127       video: this.getEncodersByPriority('video'),
 128       audio: this.getEncodersByPriority('audio')
 129     }
 130
 131     return Object.assign({}, this.availableEncoders, { encodersToTry })
 132   }
 133
 134   getAvailableProfiles (type: 'vod' | 'live') {
 135     return this.availableEncoders[type]
 136   }
 137
 138   private getEncodersByPriority (type: 'video' | 'audio') {
 139     return this.encodersPriorities[type]
 140       .sort((e1, e2) => {
 141         if (e1.priority > e2.priority) return -1
 142         else if (e1.priority === e2.priority) return 0
 143
 144         return 1
 145       })
 146       .map(e => e.name)
 147   }
 148
 149   static get Instance () {
 150     return this.instance || (this.instance = new this())
 151   }
 152 }
 153
 154 // ---------------------------------------------------------------------------
 155
 156 export {
 157   VideoTranscodingProfilesManager
 158 }
 159
 160 // ---------------------------------------------------------------------------
 161 async function buildTargetBitrate (options: {
 162   input: string
 163   resolution: VideoResolution
 164   fps: number
 165 }) {
 166   const { input, resolution, fps } = options
 167   const probe = await ffprobePromise(input)
 168
 169   const videoStream = await getVideoStreamFromFile(input, probe)
 170   if (!videoStream) return undefined
 171
 172   const targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
 173
 174   // Don't transcode to an higher bitrate than the original file
 175   const fileBitrate = await getVideoFileBitrate(input, probe)
 176   return Math.min(targetBitrate, fileBitrate)
 177 }