server/helpers/ffmpeg-utils.ts

   1 import * as ffmpeg from 'fluent-ffmpeg'
   2 import { join } from 'path'
   3 import { VideoResolution } from '../../shared/models/videos'
   4 import { CONFIG, VIDEO_TRANSCODING_FPS } from '../initializers'
   5 import { unlinkPromise } from './core-utils'
   6 import { processImage } from './image-utils'
   7 import { logger } from './logger'
   8 import { checkFFmpegEncoders } from '../initializers/checker'
   9
  10 async function getVideoFileResolution (path: string) {
  11   const videoStream = await getVideoFileStream(path)
  12
  13   return {
  14     videoFileResolution: Math.min(videoStream.height, videoStream.width),
  15     isPortraitMode: videoStream.height > videoStream.width
  16   }
  17 }
  18
  19 async function getVideoFileFPS (path: string) {
  20   const videoStream = await getVideoFileStream(path)
  21
  22   for (const key of [ 'r_frame_rate' , 'avg_frame_rate' ]) {
  23     const valuesText: string = videoStream[key]
  24     if (!valuesText) continue
  25
  26     const [ frames, seconds ] = valuesText.split('/')
  27     if (!frames || !seconds) continue
  28
  29     const result = parseInt(frames, 10) / parseInt(seconds, 10)
  30     if (result > 0) return Math.round(result)
  31   }
  32
  33   return 0
  34 }
  35
  36 function getDurationFromVideoFile (path: string) {
  37   return new Promise<number>((res, rej) => {
  38     ffmpeg.ffprobe(path, (err, metadata) => {
  39       if (err) return rej(err)
  40
  41       return res(Math.floor(metadata.format.duration))
  42     })
  43   })
  44 }
  45
  46 async function generateImageFromVideoFile (fromPath: string, folder: string, imageName: string, size: { width: number, height: number }) {
  47   const pendingImageName = 'pending-' + imageName
  48
  49   const options = {
  50     filename: pendingImageName,
  51     count: 1,
  52     folder
  53   }
  54
  55   const pendingImagePath = join(folder, pendingImageName)
  56
  57   try {
  58     await new Promise<string>((res, rej) => {
  59       ffmpeg(fromPath)
  60         .on('error', rej)
  61         .on('end', () => res(imageName))
  62         .thumbnail(options)
  63     })
  64
  65     const destination = join(folder, imageName)
  66     await processImage({ path: pendingImagePath }, destination, size)
  67   } catch (err) {
  68     logger.error('Cannot generate image from video %s.', fromPath, { err })
  69
  70     try {
  71       await unlinkPromise(pendingImagePath)
  72     } catch (err) {
  73       logger.debug('Cannot remove pending image path after generation error.', { err })
  74     }
  75   }
  76 }
  77
  78 type TranscodeOptions = {
  79   inputPath: string
  80   outputPath: string
  81   resolution?: VideoResolution
  82   isPortraitMode?: boolean
  83 }
  84
  85 function transcode (options: TranscodeOptions) {
  86   return new Promise<void>(async (res, rej) => {
  87     let command = ffmpeg(options.inputPath)
  88                     .output(options.outputPath)
  89                     .outputOption('-threads ' + CONFIG.TRANSCODING.THREADS)
  90                     .preset(standard)
  91
  92     let fps = await getVideoFileFPS(options.inputPath)
  93     if (options.resolution !== undefined) {
  94       // '?x720' or '720x?' for example
  95       const size = options.isPortraitMode === true ? `${options.resolution}x?` : `?x${options.resolution}`
  96       command = command.size(size)
  97
  98       // On small/medium resolutions, limit FPS
  99       if (
 100         options.resolution < VIDEO_TRANSCODING_FPS.KEEP_ORIGIN_FPS_RESOLUTION_MIN &&
 101         fps > VIDEO_TRANSCODING_FPS.AVERAGE
 102       ) {
 103         fps = VIDEO_TRANSCODING_FPS.AVERAGE
 104       }
 105     }
 106
 107     if (fps) {
 108       // Hard FPS limits
 109       if (fps > VIDEO_TRANSCODING_FPS.MAX) fps = VIDEO_TRANSCODING_FPS.MAX
 110       else if (fps < VIDEO_TRANSCODING_FPS.MIN) fps = VIDEO_TRANSCODING_FPS.MIN
 111
 112       command = command.withFPS(fps)
 113     }
 114
 115     command
 116       .on('error', (err, stdout, stderr) => {
 117         logger.error('Error in transcoding job.', { stdout, stderr })
 118         return rej(err)
 119       })
 120       .on('end', res)
 121       .run()
 122   })
 123 }
 124
 125 // ---------------------------------------------------------------------------
 126
 127 export {
 128   getVideoFileResolution,
 129   getDurationFromVideoFile,
 130   generateImageFromVideoFile,
 131   transcode,
 132   getVideoFileFPS
 133 }
 134
 135 // ---------------------------------------------------------------------------
 136
 137 function getVideoFileStream (path: string) {
 138   return new Promise<any>((res, rej) => {
 139     ffmpeg.ffprobe(path, (err, metadata) => {
 140       if (err) return rej(err)
 141
 142       const videoStream = metadata.streams.find(s => s.codec_type === 'video')
 143       if (!videoStream) throw new Error('Cannot find video stream of ' + path)
 144
 145       return res(videoStream)
 146     })
 147   })
 148 }
 149
 150 /**
 151  * A slightly customised version of the 'veryfast' x264 preset
 152  *
 153  * The veryfast preset is right in the sweet spot of performance
 154  * and quality. Superfast and ultrafast will give you better
 155  * performance, but then quality is noticeably worse.
 156  */
 157 function veryfast (ffmpeg) {
 158   ffmpeg
 159     .preset(standard)
 160     .outputOption('-preset:v veryfast')
 161     .outputOption(['--aq-mode=2', '--aq-strength=1.3'])
 162   /*
 163   MAIN reference: https://slhck.info/video/2017/03/01/rate-control.html
 164   Our target situation is closer to a livestream than a stream,
 165   since we want to reduce as much a possible the encoding burden,
 166   altough not to the point of a livestream where there is a hard
 167   constraint on the frames per second to be encoded.
 168
 169   why '--aq-mode=2 --aq-strength=1.3' instead of '-profile:v main'?
 170     Make up for most of the loss of grain and macroblocking
 171     with less computing power.
 172   */
 173 }
 174
 175 /**
 176  * A preset optimised for a stillimage audio video
 177  */
 178 function audio (ffmpeg) {
 179   ffmpeg
 180     .preset(veryfast)
 181     .outputOption('-tune stillimage')
 182 }
 183
 184 /**
 185  * A toolbox to play with audio
 186  */
 187 namespace audio {
 188   export const get = (ffmpeg, pos = 0) => {
 189     // without position, ffprobe considers the last input only
 190     // we make it consider the first input only
 191     ffmpeg
 192       .ffprobe(pos, (_,data) => {
 193         return data['streams'].find(stream => {
 194           return stream['codec_type'] === 'audio'
 195         })
 196       })
 197   }
 198
 199   export namespace bitrate {
 200     export const baseKbitrate = 384
 201
 202     const toBits = (kbits: number): number => { return kbits * 8000 }
 203
 204     export const aac = (bitrate: number): number => {
 205       switch (true) {
 206       case bitrate > toBits(384):
 207         return baseKbitrate
 208       default:
 209         return -1 // we interpret it as a signal to copy the audio stream as is
 210       }
 211     }
 212
 213     export const mp3 = (bitrate: number): number => {
 214       switch (true) {
 215       case bitrate <= toBits(192):
 216         return 128
 217       case bitrate <= toBits(384):
 218         return 256
 219       default:
 220         return baseKbitrate
 221       }
 222     }
 223   }
 224 }
 225
 226 /**
 227  * Standard profile, with variable bitrate audio and faststart.
 228  *
 229  * As for the audio, quality '5' is the highest and ensures 96-112kbps/channel
 230  * See https://trac.ffmpeg.org/wiki/Encode/AAC#fdk_vbr
 231  */
 232 async function standard (ffmpeg) {
 233   let _bitrate = audio.bitrate.baseKbitrate
 234   let _ffmpeg = ffmpeg
 235     .format('mp4')
 236     .videoCodec('libx264')
 237     .outputOption('-level 3.1') // 3.1 is the minimal ressource allocation for our highest supported resolution
 238     .outputOption('-b_strategy 1') // NOTE: b-strategy 1 - heuristic algorythm, 16 is optimal B-frames for it
 239     .outputOption('-bf 16') // NOTE: Why 16: https://github.com/Chocobozzz/PeerTube/pull/774. b-strategy 2 -> B-frames<16
 240     .outputOption('-movflags faststart')
 241   let _audio = audio.get(_ffmpeg)
 242
 243   if (!_audio) return _ffmpeg.noAudio()
 244
 245   // we try to reduce the ceiling bitrate by making rough correspondances of bitrates
 246   // of course this is far from perfect, but it might save some space in the end
 247   if (audio.bitrate[_audio['codec_name']]) {
 248     _bitrate = audio.bitrate[_audio['codec_name']](_audio['bit_rate'])
 249     if (_bitrate === -1) {
 250       return _ffmpeg.audioCodec('copy')
 251     }
 252   }
 253
 254   // we favor VBR, if a good AAC encoder is available
 255   if ((await checkFFmpegEncoders()).get('libfdk_aac')) {
 256     return _ffmpeg
 257       .audioCodec('libfdk_aac')
 258       .audioQuality(5)
 259   }
 260
 261   return _ffmpeg.audioBitrate(_bitrate)
 262 }