server/helpers/ffmpeg-utils.ts

   1 import * as ffmpeg from 'fluent-ffmpeg'
   2 import { join } from 'path'
   3 import { VideoResolution, getTargetBitrate } from '../../shared/models/videos'
   4 import { CONFIG, FFMPEG_NICE, VIDEO_TRANSCODING_FPS } from '../initializers'
   5 import { processImage } from './image-utils'
   6 import { logger } from './logger'
   7 import { checkFFmpegEncoders } from '../initializers/checker-before-init'
   8 import { remove } from 'fs-extra'
   9
  10 function computeResolutionsToTranscode (videoFileHeight: number) {
  11   const resolutionsEnabled: number[] = []
  12   const configResolutions = CONFIG.TRANSCODING.RESOLUTIONS
  13
  14   // Put in the order we want to proceed jobs
  15   const resolutions = [
  16     VideoResolution.H_480P,
  17     VideoResolution.H_360P,
  18     VideoResolution.H_720P,
  19     VideoResolution.H_240P,
  20     VideoResolution.H_1080P
  21   ]
  22
  23   for (const resolution of resolutions) {
  24     if (configResolutions[ resolution + 'p' ] === true && videoFileHeight > resolution) {
  25       resolutionsEnabled.push(resolution)
  26     }
  27   }
  28
  29   return resolutionsEnabled
  30 }
  31
  32 async function getVideoFileResolution (path: string) {
  33   const videoStream = await getVideoFileStream(path)
  34
  35   return {
  36     videoFileResolution: Math.min(videoStream.height, videoStream.width),
  37     isPortraitMode: videoStream.height > videoStream.width
  38   }
  39 }
  40
  41 async function getVideoFileFPS (path: string) {
  42   const videoStream = await getVideoFileStream(path)
  43
  44   for (const key of [ 'r_frame_rate' , 'avg_frame_rate' ]) {
  45     const valuesText: string = videoStream[key]
  46     if (!valuesText) continue
  47
  48     const [ frames, seconds ] = valuesText.split('/')
  49     if (!frames || !seconds) continue
  50
  51     const result = parseInt(frames, 10) / parseInt(seconds, 10)
  52     if (result > 0) return Math.round(result)
  53   }
  54
  55   return 0
  56 }
  57
  58 async function getVideoFileBitrate (path: string) {
  59   return new Promise<number>((res, rej) => {
  60     ffmpeg.ffprobe(path, (err, metadata) => {
  61       if (err) return rej(err)
  62
  63       return res(metadata.format.bit_rate)
  64     })
  65   })
  66 }
  67
  68 function getDurationFromVideoFile (path: string) {
  69   return new Promise<number>((res, rej) => {
  70     ffmpeg.ffprobe(path, (err, metadata) => {
  71       if (err) return rej(err)
  72
  73       return res(Math.floor(metadata.format.duration))
  74     })
  75   })
  76 }
  77
  78 async function generateImageFromVideoFile (fromPath: string, folder: string, imageName: string, size: { width: number, height: number }) {
  79   const pendingImageName = 'pending-' + imageName
  80
  81   const options = {
  82     filename: pendingImageName,
  83     count: 1,
  84     folder
  85   }
  86
  87   const pendingImagePath = join(folder, pendingImageName)
  88
  89   try {
  90     await new Promise<string>((res, rej) => {
  91       ffmpeg(fromPath, { niceness: FFMPEG_NICE.THUMBNAIL })
  92         .on('error', rej)
  93         .on('end', () => res(imageName))
  94         .thumbnail(options)
  95     })
  96
  97     const destination = join(folder, imageName)
  98     await processImage({ path: pendingImagePath }, destination, size)
  99   } catch (err) {
 100     logger.error('Cannot generate image from video %s.', fromPath, { err })
 101
 102     try {
 103       await remove(pendingImagePath)
 104     } catch (err) {
 105       logger.debug('Cannot remove pending image path after generation error.', { err })
 106     }
 107   }
 108 }
 109
 110 type TranscodeOptions = {
 111   inputPath: string
 112   outputPath: string
 113   resolution?: VideoResolution
 114   isPortraitMode?: boolean
 115 }
 116
 117 function transcode (options: TranscodeOptions) {
 118   return new Promise<void>(async (res, rej) => {
 119     let command = ffmpeg(options.inputPath, { niceness: FFMPEG_NICE.TRANSCODING })
 120                     .output(options.outputPath)
 121                     .preset(standard)
 122
 123     if (CONFIG.TRANSCODING.THREADS > 0) {
 124       // if we don't set any threads ffmpeg will chose automatically
 125       command = command.outputOption('-threads ' + CONFIG.TRANSCODING.THREADS)
 126     }
 127
 128     let fps = await getVideoFileFPS(options.inputPath)
 129     if (options.resolution !== undefined) {
 130       // '?x720' or '720x?' for example
 131       const size = options.isPortraitMode === true ? `${options.resolution}x?` : `?x${options.resolution}`
 132       command = command.size(size)
 133
 134       // On small/medium resolutions, limit FPS
 135       if (
 136         options.resolution < VIDEO_TRANSCODING_FPS.KEEP_ORIGIN_FPS_RESOLUTION_MIN &&
 137         fps > VIDEO_TRANSCODING_FPS.AVERAGE
 138       ) {
 139         fps = VIDEO_TRANSCODING_FPS.AVERAGE
 140       }
 141     }
 142
 143     if (fps) {
 144       // Hard FPS limits
 145       if (fps > VIDEO_TRANSCODING_FPS.MAX) fps = VIDEO_TRANSCODING_FPS.MAX
 146       else if (fps < VIDEO_TRANSCODING_FPS.MIN) fps = VIDEO_TRANSCODING_FPS.MIN
 147
 148       command = command.withFPS(fps)
 149     }
 150
 151     // Constrained Encoding (VBV)
 152     // https://slhck.info/video/2017/03/01/rate-control.html
 153     // https://trac.ffmpeg.org/wiki/Limiting%20the%20output%20bitrate
 154     const targetBitrate = getTargetBitrate(options.resolution, fps, VIDEO_TRANSCODING_FPS)
 155     command.outputOptions([`-maxrate ${ targetBitrate }`, `-bufsize ${ targetBitrate * 2 }`])
 156
 157     command
 158       .on('error', (err, stdout, stderr) => {
 159         logger.error('Error in transcoding job.', { stdout, stderr })
 160         return rej(err)
 161       })
 162       .on('end', res)
 163       .run()
 164   })
 165 }
 166
 167 // ---------------------------------------------------------------------------
 168
 169 export {
 170   getVideoFileResolution,
 171   getDurationFromVideoFile,
 172   generateImageFromVideoFile,
 173   transcode,
 174   getVideoFileFPS,
 175   computeResolutionsToTranscode,
 176   audio,
 177   getVideoFileBitrate
 178 }
 179
 180 // ---------------------------------------------------------------------------
 181
 182 function getVideoFileStream (path: string) {
 183   return new Promise<any>((res, rej) => {
 184     ffmpeg.ffprobe(path, (err, metadata) => {
 185       if (err) return rej(err)
 186
 187       const videoStream = metadata.streams.find(s => s.codec_type === 'video')
 188       if (!videoStream) throw new Error('Cannot find video stream of ' + path)
 189
 190       return res(videoStream)
 191     })
 192   })
 193 }
 194
 195 /**
 196  * A slightly customised version of the 'veryfast' x264 preset
 197  *
 198  * The veryfast preset is right in the sweet spot of performance
 199  * and quality. Superfast and ultrafast will give you better
 200  * performance, but then quality is noticeably worse.
 201  */
 202 function veryfast (_ffmpeg) {
 203   _ffmpeg
 204     .preset(standard)
 205     .outputOption('-preset:v veryfast')
 206     .outputOption(['--aq-mode=2', '--aq-strength=1.3'])
 207   /*
 208   MAIN reference: https://slhck.info/video/2017/03/01/rate-control.html
 209   Our target situation is closer to a livestream than a stream,
 210   since we want to reduce as much a possible the encoding burden,
 211   altough not to the point of a livestream where there is a hard
 212   constraint on the frames per second to be encoded.
 213
 214   why '--aq-mode=2 --aq-strength=1.3' instead of '-profile:v main'?
 215     Make up for most of the loss of grain and macroblocking
 216     with less computing power.
 217   */
 218 }
 219
 220 /**
 221  * A preset optimised for a stillimage audio video
 222  */
 223 function audio (_ffmpeg) {
 224   _ffmpeg
 225     .preset(veryfast)
 226     .outputOption('-tune stillimage')
 227 }
 228
 229 /**
 230  * A toolbox to play with audio
 231  */
 232 namespace audio {
 233   export const get = (_ffmpeg, pos: number | string = 0) => {
 234     // without position, ffprobe considers the last input only
 235     // we make it consider the first input only
 236     // if you pass a file path to pos, then ffprobe acts on that file directly
 237     return new Promise<{ absolutePath: string, audioStream?: any }>((res, rej) => {
 238       _ffmpeg.ffprobe(pos, (err,data) => {
 239         if (err) return rej(err)
 240
 241         if ('streams' in data) {
 242           const audioStream = data['streams'].find(stream => stream['codec_type'] === 'audio')
 243           if (audioStream) {
 244             return res({
 245               absolutePath: data.format.filename,
 246               audioStream
 247             })
 248           }
 249         }
 250         return res({ absolutePath: data.format.filename })
 251       })
 252     })
 253   }
 254
 255   export namespace bitrate {
 256     const baseKbitrate = 384
 257
 258     const toBits = (kbits: number): number => { return kbits * 8000 }
 259
 260     export const aac = (bitrate: number): number => {
 261       switch (true) {
 262       case bitrate > toBits(baseKbitrate):
 263         return baseKbitrate
 264       default:
 265         return -1 // we interpret it as a signal to copy the audio stream as is
 266       }
 267     }
 268
 269     export const mp3 = (bitrate: number): number => {
 270       /*
 271       a 192kbit/sec mp3 doesn't hold as much information as a 192kbit/sec aac.
 272       That's why, when using aac, we can go to lower kbit/sec. The equivalences
 273       made here are not made to be accurate, especially with good mp3 encoders.
 274       */
 275       switch (true) {
 276       case bitrate <= toBits(192):
 277         return 128
 278       case bitrate <= toBits(384):
 279         return 256
 280       default:
 281         return baseKbitrate
 282       }
 283     }
 284   }
 285 }
 286
 287 /**
 288  * Standard profile, with variable bitrate audio and faststart.
 289  *
 290  * As for the audio, quality '5' is the highest and ensures 96-112kbps/channel
 291  * See https://trac.ffmpeg.org/wiki/Encode/AAC#fdk_vbr
 292  */
 293 async function standard (_ffmpeg) {
 294   let localFfmpeg = _ffmpeg
 295     .format('mp4')
 296     .videoCodec('libx264')
 297     .outputOption('-level 3.1') // 3.1 is the minimal ressource allocation for our highest supported resolution
 298     .outputOption('-b_strategy 1') // NOTE: b-strategy 1 - heuristic algorythm, 16 is optimal B-frames for it
 299     .outputOption('-bf 16') // NOTE: Why 16: https://github.com/Chocobozzz/PeerTube/pull/774. b-strategy 2 -> B-frames<16
 300     .outputOption('-map_metadata -1') // strip all metadata
 301     .outputOption('-movflags faststart')
 302   const _audio = await audio.get(localFfmpeg)
 303
 304   if (!_audio.audioStream) {
 305     return localFfmpeg.noAudio()
 306   }
 307
 308   // we favor VBR, if a good AAC encoder is available
 309   if ((await checkFFmpegEncoders()).get('libfdk_aac')) {
 310     return localFfmpeg
 311       .audioCodec('libfdk_aac')
 312       .audioQuality(5)
 313   }
 314
 315   // we try to reduce the ceiling bitrate by making rough correspondances of bitrates
 316   // of course this is far from perfect, but it might save some space in the end
 317   const audioCodecName = _audio.audioStream['codec_name']
 318   let bitrate: number
 319   if (audio.bitrate[audioCodecName]) {
 320     bitrate = audio.bitrate[audioCodecName](_audio.audioStream['bit_rate'])
 321
 322     if (bitrate === -1) return localFfmpeg.audioCodec('copy')
 323   }
 324
 325   if (bitrate !== undefined) return localFfmpeg.audioBitrate(bitrate)
 326
 327   return localFfmpeg
 328 }