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 fps = await getVideoFileFPS(options.inputPath)
 120     // On small/medium resolutions, limit FPS
 121     if (options.resolution !== undefined &&
 122         options.resolution < VIDEO_TRANSCODING_FPS.KEEP_ORIGIN_FPS_RESOLUTION_MIN &&
 123         fps > VIDEO_TRANSCODING_FPS.AVERAGE) {
 124       fps = VIDEO_TRANSCODING_FPS.AVERAGE
 125     }
 126
 127     let command = ffmpeg(options.inputPath, { niceness: FFMPEG_NICE.TRANSCODING })
 128                     .output(options.outputPath)
 129     command = await presetH264(command, options.resolution, fps)
 130
 131     if (CONFIG.TRANSCODING.THREADS > 0) {
 132       // if we don't set any threads ffmpeg will chose automatically
 133       command = command.outputOption('-threads ' + CONFIG.TRANSCODING.THREADS)
 134     }
 135
 136     if (options.resolution !== undefined) {
 137       // '?x720' or '720x?' for example
 138       const size = options.isPortraitMode === true ? `${options.resolution}x?` : `?x${options.resolution}`
 139       command = command.size(size)
 140     }
 141
 142     if (fps) {
 143       // Hard FPS limits
 144       if (fps > VIDEO_TRANSCODING_FPS.MAX) fps = VIDEO_TRANSCODING_FPS.MAX
 145       else if (fps < VIDEO_TRANSCODING_FPS.MIN) fps = VIDEO_TRANSCODING_FPS.MIN
 146
 147       command = command.withFPS(fps)
 148     }
 149
 150     command
 151       .on('error', (err, stdout, stderr) => {
 152         logger.error('Error in transcoding job.', { stdout, stderr })
 153         return rej(err)
 154       })
 155       .on('end', res)
 156       .run()
 157   })
 158 }
 159
 160 // ---------------------------------------------------------------------------
 161
 162 export {
 163   getVideoFileResolution,
 164   getDurationFromVideoFile,
 165   generateImageFromVideoFile,
 166   transcode,
 167   getVideoFileFPS,
 168   computeResolutionsToTranscode,
 169   audio,
 170   getVideoFileBitrate
 171 }
 172
 173 // ---------------------------------------------------------------------------
 174
 175 function getVideoFileStream (path: string) {
 176   return new Promise<any>((res, rej) => {
 177     ffmpeg.ffprobe(path, (err, metadata) => {
 178       if (err) return rej(err)
 179
 180       const videoStream = metadata.streams.find(s => s.codec_type === 'video')
 181       if (!videoStream) throw new Error('Cannot find video stream of ' + path)
 182
 183       return res(videoStream)
 184     })
 185   })
 186 }
 187
 188 /**
 189  * A slightly customised version of the 'veryfast' x264 preset
 190  *
 191  * The veryfast preset is right in the sweet spot of performance
 192  * and quality. Superfast and ultrafast will give you better
 193  * performance, but then quality is noticeably worse.
 194  */
 195 async function presetH264VeryFast (ffmpeg: ffmpeg, resolution: VideoResolution, fps: number): ffmpeg {
 196   const localFfmpeg = await presetH264(ffmpeg, resolution, fps)
 197   localFfmpeg
 198     .outputOption('-preset:v veryfast')
 199     .outputOption(['--aq-mode=2', '--aq-strength=1.3'])
 200   /*
 201   MAIN reference: https://slhck.info/video/2017/03/01/rate-control.html
 202   Our target situation is closer to a livestream than a stream,
 203   since we want to reduce as much a possible the encoding burden,
 204   altough not to the point of a livestream where there is a hard
 205   constraint on the frames per second to be encoded.
 206
 207   why '--aq-mode=2 --aq-strength=1.3' instead of '-profile:v main'?
 208     Make up for most of the loss of grain and macroblocking
 209     with less computing power.
 210   */
 211 }
 212
 213 /**
 214  * A preset optimised for a stillimage audio video
 215  */
 216 async function presetStillImageWithAudio (ffmpeg: ffmpeg, resolution: VideoResolution, fps: number): ffmpeg {
 217   const localFfmpeg = await presetH264VeryFast(ffmpeg, resolution, fps)
 218   localFfmpeg
 219     .outputOption('-tune stillimage')
 220 }
 221
 222 /**
 223  * A toolbox to play with audio
 224  */
 225 namespace audio {
 226   export const get = (_ffmpeg, pos: number | string = 0) => {
 227     // without position, ffprobe considers the last input only
 228     // we make it consider the first input only
 229     // if you pass a file path to pos, then ffprobe acts on that file directly
 230     return new Promise<{ absolutePath: string, audioStream?: any }>((res, rej) => {
 231       _ffmpeg.ffprobe(pos, (err,data) => {
 232         if (err) return rej(err)
 233
 234         if ('streams' in data) {
 235           const audioStream = data['streams'].find(stream => stream['codec_type'] === 'audio')
 236           if (audioStream) {
 237             return res({
 238               absolutePath: data.format.filename,
 239               audioStream
 240             })
 241           }
 242         }
 243         return res({ absolutePath: data.format.filename })
 244       })
 245     })
 246   }
 247
 248   export namespace bitrate {
 249     const baseKbitrate = 384
 250
 251     const toBits = (kbits: number): number => { return kbits * 8000 }
 252
 253     export const aac = (bitrate: number): number => {
 254       switch (true) {
 255       case bitrate > toBits(baseKbitrate):
 256         return baseKbitrate
 257       default:
 258         return -1 // we interpret it as a signal to copy the audio stream as is
 259       }
 260     }
 261
 262     export const mp3 = (bitrate: number): number => {
 263       /*
 264       a 192kbit/sec mp3 doesn't hold as much information as a 192kbit/sec aac.
 265       That's why, when using aac, we can go to lower kbit/sec. The equivalences
 266       made here are not made to be accurate, especially with good mp3 encoders.
 267       */
 268       switch (true) {
 269       case bitrate <= toBits(192):
 270         return 128
 271       case bitrate <= toBits(384):
 272         return 256
 273       default:
 274         return baseKbitrate
 275       }
 276     }
 277   }
 278 }
 279
 280 /**
 281  * Standard profile, with variable bitrate audio and faststart.
 282  *
 283  * As for the audio, quality '5' is the highest and ensures 96-112kbps/channel
 284  * See https://trac.ffmpeg.org/wiki/Encode/AAC#fdk_vbr
 285  */
 286 async function presetH264 (ffmpeg: ffmpeg, resolution: VideoResolution, fps: number): ffmpeg {
 287   let localFfmpeg = ffmpeg
 288     .format('mp4')
 289     .videoCodec('libx264')
 290     .outputOption('-level 3.1') // 3.1 is the minimal ressource allocation for our highest supported resolution
 291     .outputOption('-b_strategy 1') // NOTE: b-strategy 1 - heuristic algorythm, 16 is optimal B-frames for it
 292     .outputOption('-bf 16') // NOTE: Why 16: https://github.com/Chocobozzz/PeerTube/pull/774. b-strategy 2 -> B-frames<16
 293     .outputOption('-map_metadata -1') // strip all metadata
 294     .outputOption('-movflags faststart')
 295   const _audio = await audio.get(localFfmpeg)
 296
 297   if (!_audio.audioStream) {
 298     return localFfmpeg.noAudio()
 299   }
 300
 301   // we favor VBR, if a good AAC encoder is available
 302   if ((await checkFFmpegEncoders()).get('libfdk_aac')) {
 303     return localFfmpeg
 304       .audioCodec('libfdk_aac')
 305       .audioQuality(5)
 306   }
 307
 308   // we try to reduce the ceiling bitrate by making rough correspondances of bitrates
 309   // of course this is far from perfect, but it might save some space in the end
 310   const audioCodecName = _audio.audioStream['codec_name']
 311   let bitrate: number
 312   if (audio.bitrate[audioCodecName]) {
 313     bitrate = audio.bitrate[audioCodecName](_audio.audioStream['bit_rate'])
 314
 315     if (bitrate === -1) return localFfmpeg.audioCodec('copy')
 316   }
 317
 318   if (bitrate !== undefined) return localFfmpeg.audioBitrate(bitrate)
 319
 320   // Constrained Encoding (VBV)
 321   // https://slhck.info/video/2017/03/01/rate-control.html
 322   // https://trac.ffmpeg.org/wiki/Limiting%20the%20output%20bitrate
 323   const targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
 324   localFfmpeg.outputOptions([`-maxrate ${ targetBitrate }`, `-bufsize ${ targetBitrate * 2 }`])
 325
 326   // Keyframe interval of 2 seconds for faster seeking and resolution switching.
 327   // https://streaminglearningcenter.com/blogs/whats-the-right-keyframe-interval.html
 328   // https://superuser.com/a/908325
 329   localFfmpeg.outputOption(`-g ${ fps * 2 }`)
 330
 331   return localFfmpeg
 332 }