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 const availableEncoders: AvailableEncoders = {
  82   vod: {
  83     libx264: {
  84       default: defaultX264VODOptionsBuilder
  85     },
  86     aac: {
  87       default: defaultAACOptionsBuilder
  88     },
  89     libfdk_aac: {
  90       default: defaultLibFDKAACVODOptionsBuilder
  91     }
  92   },
  93   live: {
  94     libx264: {
  95       default: defaultX264LiveOptionsBuilder
  96     },
  97     aac: {
  98       default: defaultAACOptionsBuilder
  99     }
 100   }
 101 }
 102
 103 // ---------------------------------------------------------------------------
 104
 105 export {
 106   availableEncoders
 107 }
 108
 109 // ---------------------------------------------------------------------------
 110 async function buildTargetBitrate (options: {
 111   input: string
 112   resolution: VideoResolution
 113   fps: number
 114 }) {
 115   const { input, resolution, fps } = options
 116   const probe = await ffprobePromise(input)
 117
 118   const videoStream = await getVideoStreamFromFile(input, probe)
 119   if (!videoStream) return undefined
 120
 121   const targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
 122
 123   // Don't transcode to an higher bitrate than the original file
 124   const fileBitrate = await getVideoFileBitrate(input, probe)
 125   return Math.min(targetBitrate, fileBitrate)
 126 }