server/lib/video-transcoding-profiles.ts

   1 import { logger } from '@server/helpers/logger'
   2 import { getTargetBitrate } 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   let targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
  27
  28   const probe = await ffprobePromise(input)
  29
  30   const videoStream = await getVideoStreamFromFile(input, probe)
  31   if (!videoStream) {
  32     return { outputOptions: [ ] }
  33   }
  34
  35   // Don't transcode to an higher bitrate than the original file
  36   const fileBitrate = await getVideoFileBitrate(input, probe)
  37   targetBitrate = Math.min(targetBitrate, fileBitrate)
  38
  39   return {
  40     outputOptions: [
  41       `-maxrate ${targetBitrate}`,
  42       `-bufsize ${targetBitrate * 2}`
  43     ]
  44   }
  45 }
  46
  47 const defaultX264LiveOptionsBuilder: EncoderOptionsBuilder = async ({ resolution, fps, streamNum }) => {
  48   const targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
  49
  50   return {
  51     outputOptions: [
  52       `${buildStreamSuffix('-b:v', streamNum)} ${targetBitrate}`,
  53       `-maxrate ${targetBitrate}`,
  54       `-bufsize ${targetBitrate * 2}`
  55     ]
  56   }
  57 }
  58
  59 const defaultAACOptionsBuilder: EncoderOptionsBuilder = async ({ input, streamNum }) => {
  60   const probe = await ffprobePromise(input)
  61
  62   if (await canDoQuickAudioTranscode(input, probe)) {
  63     logger.debug('Copy audio stream %s by AAC encoder.', input)
  64     return { copy: true, outputOptions: [] }
  65   }
  66
  67   const parsedAudio = await getAudioStream(input, probe)
  68
  69   // We try to reduce the ceiling bitrate by making rough matches of bitrates
  70   // Of course this is far from perfect, but it might save some space in the end
  71
  72   const audioCodecName = parsedAudio.audioStream['codec_name']
  73
  74   const bitrate = getMaxAudioBitrate(audioCodecName, parsedAudio.bitrate)
  75
  76   logger.debug('Calculating audio bitrate of %s by AAC encoder.', input, { bitrate: parsedAudio.bitrate, audioCodecName })
  77
  78   if (bitrate !== undefined && bitrate !== -1) {
  79     return { outputOptions: [ buildStreamSuffix('-b:a', streamNum), bitrate + 'k' ] }
  80   }
  81
  82   return { outputOptions: [ ] }
  83 }
  84
  85 const defaultLibFDKAACVODOptionsBuilder: EncoderOptionsBuilder = ({ streamNum }) => {
  86   return { outputOptions: [ buildStreamSuffix('-q:a', streamNum), '5' ] }
  87 }
  88
  89 const availableEncoders: AvailableEncoders = {
  90   vod: {
  91     libx264: {
  92       default: defaultX264VODOptionsBuilder
  93     },
  94     aac: {
  95       default: defaultAACOptionsBuilder
  96     },
  97     libfdk_aac: {
  98       default: defaultLibFDKAACVODOptionsBuilder
  99     }
 100   },
 101   live: {
 102     libx264: {
 103       default: defaultX264LiveOptionsBuilder
 104     },
 105     aac: {
 106       default: defaultAACOptionsBuilder
 107     }
 108   }
 109 }
 110
 111 // ---------------------------------------------------------------------------
 112
 113 export {
 114   availableEncoders
 115 }
 116
 117 // ---------------------------------------------------------------------------