PeerTube/server/helpers/ffmpeg-utils.ts

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import * as ffmpeg from 'fluent-ffmpeg'
import { join } from 'path'
import { VideoResolution, getTargetBitrate } from '../../shared/models/videos'
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import { CONFIG, FFMPEG_NICE, VIDEO_TRANSCODING_FPS } from '../initializers'
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import { processImage } from './image-utils'
import { logger } from './logger'
import { checkFFmpegEncoders } from '../initializers/checker-before-init'
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import { remove } from 'fs-extra'
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function computeResolutionsToTranscode (videoFileHeight: number) {
const resolutionsEnabled: number[] = []
const configResolutions = CONFIG.TRANSCODING.RESOLUTIONS
// Put in the order we want to proceed jobs
const resolutions = [
VideoResolution.H_480P,
VideoResolution.H_360P,
VideoResolution.H_720P,
VideoResolution.H_240P,
VideoResolution.H_1080P
]
for (const resolution of resolutions) {
if (configResolutions[ resolution + 'p' ] === true && videoFileHeight > resolution) {
resolutionsEnabled.push(resolution)
}
}
return resolutionsEnabled
}
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async function getVideoFileResolution (path: string) {
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const videoStream = await getVideoFileStream(path)
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return {
videoFileResolution: Math.min(videoStream.height, videoStream.width),
isPortraitMode: videoStream.height > videoStream.width
}
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}
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async function getVideoFileFPS (path: string) {
const videoStream = await getVideoFileStream(path)
for (const key of [ 'r_frame_rate' , 'avg_frame_rate' ]) {
const valuesText: string = videoStream[key]
if (!valuesText) continue
const [ frames, seconds ] = valuesText.split('/')
if (!frames || !seconds) continue
const result = parseInt(frames, 10) / parseInt(seconds, 10)
if (result > 0) return Math.round(result)
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}
return 0
}
async function getVideoFileBitrate (path: string) {
return new Promise<number>((res, rej) => {
ffmpeg.ffprobe(path, (err, metadata) => {
if (err) return rej(err)
return res(metadata.format.bit_rate)
})
})
}
function getDurationFromVideoFile (path: string) {
return new Promise<number>((res, rej) => {
ffmpeg.ffprobe(path, (err, metadata) => {
if (err) return rej(err)
return res(Math.floor(metadata.format.duration))
})
})
}
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async function generateImageFromVideoFile (fromPath: string, folder: string, imageName: string, size: { width: number, height: number }) {
const pendingImageName = 'pending-' + imageName
const options = {
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filename: pendingImageName,
count: 1,
folder
}
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const pendingImagePath = join(folder, pendingImageName)
try {
await new Promise<string>((res, rej) => {
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ffmpeg(fromPath, { niceness: FFMPEG_NICE.THUMBNAIL })
.on('error', rej)
.on('end', () => res(imageName))
.thumbnail(options)
})
const destination = join(folder, imageName)
await processImage({ path: pendingImagePath }, destination, size)
} catch (err) {
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logger.error('Cannot generate image from video %s.', fromPath, { err })
try {
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await remove(pendingImagePath)
} catch (err) {
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logger.debug('Cannot remove pending image path after generation error.', { err })
}
}
}
type TranscodeOptions = {
inputPath: string
outputPath: string
resolution?: VideoResolution
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isPortraitMode?: boolean
}
function transcode (options: TranscodeOptions) {
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return new Promise<void>(async (res, rej) => {
let fps = await getVideoFileFPS(options.inputPath)
// On small/medium resolutions, limit FPS
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if (
options.resolution !== undefined &&
options.resolution < VIDEO_TRANSCODING_FPS.KEEP_ORIGIN_FPS_RESOLUTION_MIN &&
fps > VIDEO_TRANSCODING_FPS.AVERAGE
) {
fps = VIDEO_TRANSCODING_FPS.AVERAGE
}
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let command = ffmpeg(options.inputPath, { niceness: FFMPEG_NICE.TRANSCODING })
.output(options.outputPath)
command = await presetH264(command, options.resolution, fps)
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if (CONFIG.TRANSCODING.THREADS > 0) {
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// if we don't set any threads ffmpeg will chose automatically
command = command.outputOption('-threads ' + CONFIG.TRANSCODING.THREADS)
}
if (options.resolution !== undefined) {
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// '?x720' or '720x?' for example
const size = options.isPortraitMode === true ? `${options.resolution}x?` : `?x${options.resolution}`
command = command.size(size)
}
if (fps) {
// Hard FPS limits
if (fps > VIDEO_TRANSCODING_FPS.MAX) fps = VIDEO_TRANSCODING_FPS.MAX
else if (fps < VIDEO_TRANSCODING_FPS.MIN) fps = VIDEO_TRANSCODING_FPS.MIN
command = command.withFPS(fps)
}
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command
.on('error', (err, stdout, stderr) => {
logger.error('Error in transcoding job.', { stdout, stderr })
return rej(err)
})
.on('end', res)
.run()
})
}
// ---------------------------------------------------------------------------
export {
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getVideoFileResolution,
getDurationFromVideoFile,
generateImageFromVideoFile,
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transcode,
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getVideoFileFPS,
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computeResolutionsToTranscode,
audio,
getVideoFileBitrate
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}
// ---------------------------------------------------------------------------
function getVideoFileStream (path: string) {
return new Promise<any>((res, rej) => {
ffmpeg.ffprobe(path, (err, metadata) => {
if (err) return rej(err)
const videoStream = metadata.streams.find(s => s.codec_type === 'video')
if (!videoStream) throw new Error('Cannot find video stream of ' + path)
return res(videoStream)
})
})
}
/**
* A slightly customised version of the 'veryfast' x264 preset
*
* The veryfast preset is right in the sweet spot of performance
* and quality. Superfast and ultrafast will give you better
* performance, but then quality is noticeably worse.
*/
async function presetH264VeryFast (ffmpeg: ffmpeg, resolution: VideoResolution, fps: number): ffmpeg {
const localFfmpeg = await presetH264(ffmpeg, resolution, fps)
localFfmpeg
.outputOption('-preset:v veryfast')
.outputOption(['--aq-mode=2', '--aq-strength=1.3'])
/*
MAIN reference: https://slhck.info/video/2017/03/01/rate-control.html
Our target situation is closer to a livestream than a stream,
since we want to reduce as much a possible the encoding burden,
altough not to the point of a livestream where there is a hard
constraint on the frames per second to be encoded.
why '--aq-mode=2 --aq-strength=1.3' instead of '-profile:v main'?
Make up for most of the loss of grain and macroblocking
with less computing power.
*/
}
/**
* A preset optimised for a stillimage audio video
*/
async function presetStillImageWithAudio (ffmpeg: ffmpeg, resolution: VideoResolution, fps: number): ffmpeg {
const localFfmpeg = await presetH264VeryFast(ffmpeg, resolution, fps)
localFfmpeg
.outputOption('-tune stillimage')
}
/**
* A toolbox to play with audio
*/
namespace audio {
export const get = (_ffmpeg, pos: number | string = 0) => {
// without position, ffprobe considers the last input only
// we make it consider the first input only
// if you pass a file path to pos, then ffprobe acts on that file directly
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return new Promise<{ absolutePath: string, audioStream?: any }>((res, rej) => {
_ffmpeg.ffprobe(pos, (err,data) => {
if (err) return rej(err)
if ('streams' in data) {
const audioStream = data['streams'].find(stream => stream['codec_type'] === 'audio')
if (audioStream) {
return res({
absolutePath: data.format.filename,
audioStream
})
}
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}
return res({ absolutePath: data.format.filename })
})
})
}
export namespace bitrate {
const baseKbitrate = 384
const toBits = (kbits: number): number => { return kbits * 8000 }
export const aac = (bitrate: number): number => {
switch (true) {
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case bitrate > toBits(baseKbitrate):
return baseKbitrate
default:
return -1 // we interpret it as a signal to copy the audio stream as is
}
}
export const mp3 = (bitrate: number): number => {
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/*
a 192kbit/sec mp3 doesn't hold as much information as a 192kbit/sec aac.
That's why, when using aac, we can go to lower kbit/sec. The equivalences
made here are not made to be accurate, especially with good mp3 encoders.
*/
switch (true) {
case bitrate <= toBits(192):
return 128
case bitrate <= toBits(384):
return 256
default:
return baseKbitrate
}
}
}
}
/**
* Standard profile, with variable bitrate audio and faststart.
*
* As for the audio, quality '5' is the highest and ensures 96-112kbps/channel
* See https://trac.ffmpeg.org/wiki/Encode/AAC#fdk_vbr
*/
async function presetH264 (ffmpeg: ffmpeg, resolution: VideoResolution, fps: number): ffmpeg {
let localFfmpeg = ffmpeg
.format('mp4')
.videoCodec('libx264')
.outputOption('-level 3.1') // 3.1 is the minimal ressource allocation for our highest supported resolution
.outputOption('-b_strategy 1') // NOTE: b-strategy 1 - heuristic algorythm, 16 is optimal B-frames for it
.outputOption('-bf 16') // NOTE: Why 16: https://github.com/Chocobozzz/PeerTube/pull/774. b-strategy 2 -> B-frames<16
.outputOption('-map_metadata -1') // strip all metadata
.outputOption('-movflags faststart')
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const _audio = await audio.get(localFfmpeg)
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if (!_audio.audioStream) {
return localFfmpeg.noAudio()
}
// we favor VBR, if a good AAC encoder is available
if ((await checkFFmpegEncoders()).get('libfdk_aac')) {
return localFfmpeg
.audioCodec('libfdk_aac')
.audioQuality(5)
}
// we try to reduce the ceiling bitrate by making rough correspondances of bitrates
// of course this is far from perfect, but it might save some space in the end
const audioCodecName = _audio.audioStream['codec_name']
let bitrate: number
if (audio.bitrate[audioCodecName]) {
bitrate = audio.bitrate[audioCodecName](_audio.audioStream['bit_rate'])
if (bitrate === -1) return localFfmpeg.audioCodec('copy')
}
if (bitrate !== undefined) return localFfmpeg.audioBitrate(bitrate)
// Constrained Encoding (VBV)
// https://slhck.info/video/2017/03/01/rate-control.html
// https://trac.ffmpeg.org/wiki/Limiting%20the%20output%20bitrate
const targetBitrate = getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)
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localFfmpeg = localFfmpeg.outputOptions([`-maxrate ${ targetBitrate }`, `-bufsize ${ targetBitrate * 2 }`])
// Keyframe interval of 2 seconds for faster seeking and resolution switching.
// https://streaminglearningcenter.com/blogs/whats-the-right-keyframe-interval.html
// https://superuser.com/a/908325
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localFfmpeg = localFfmpeg.outputOption(`-g ${ fps * 2 }`)
return localFfmpeg
}