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Fixing #626 with ffmpeg's low default audio bitrate

This commit is contained in:
Rigel Kent 2018-05-21 13:14:29 +02:00 committed by Chocobozzz
parent e80687c458
commit 4176e227cb
4 changed files with 153 additions and 16 deletions
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121
server/helpers/ffmpeg-utils.ts
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@ -5,6 +5,7 @@ import { CONFIG, VIDEO_TRANSCODING_FPS } from '../initializers'
import { unlinkPromise } from './core-utils'
import { processImage } from './image-utils'
import { logger } from './logger'
import { checkFFmpegEncoders } from '../initializers/checker'
async function getVideoFileResolution (path: string) {
const videoStream = await getVideoFileStream(path)
@ -85,12 +86,8 @@ function transcode (options: TranscodeOptions) {
return new Promise<void>(async (res, rej) => {
let command = ffmpeg(options.inputPath)
.output(options.outputPath)
.videoCodec('libx264')
.outputOption('-threads ' + CONFIG.TRANSCODING.THREADS)
.outputOption('-movflags faststart')
.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('-crf 18')
.preset(standard)
let fps = await getVideoFileFPS(options.inputPath)
if (options.resolution !== undefined) {
@ -149,3 +146,117 @@ function getVideoFileStream (path: string) {
})
})
}
/**
* 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.
*/
function veryfast (ffmpeg) {
ffmpeg
.preset(standard)
.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
*/
function audio (ffmpeg) {
ffmpeg
.preset(veryfast)
.outputOption('-tune stillimage')
}
/**
* A toolbox to play with audio
*/
namespace audio {
export const get = (ffmpeg, pos = 0) => {
// without position, ffprobe considers the last input only
// we make it consider the first input only
ffmpeg
.ffprobe(pos, (_,data) => {
return data['streams'].find(stream => {
return stream['codec_type'] === 'audio'
})
})
}
export namespace bitrate {
export const baseKbitrate = 384
const toBits = (kbits: number): number => { return kbits * 8000 }
export const aac = (bitrate: number): number => {
switch (true) {
case bitrate > toBits(384):
return baseKbitrate
default:
return -1 // we interpret it as a signal to copy the audio stream as is
}
}
export const mp3 = (bitrate: number): number => {
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 standard (ffmpeg) {
let _bitrate = audio.bitrate.baseKbitrate
let _ffmpeg = 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('-movflags faststart')
let _audio = audio.get(_ffmpeg)
if (!_audio) return _ffmpeg.noAudio()
// 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
if (audio.bitrate[_audio['codec_name']]) {
_bitrate = audio.bitrate[_audio['codec_name']](_audio['bit_rate'])
if (_bitrate === -1) {
return _ffmpeg.audioCodec('copy')
}
}
// we favor VBR, if a good AAC encoder is available
if ((await checkFFmpegEncoders()).get('libfdk_aac')) {
return _ffmpeg
.audioCodec('libfdk_aac')
.audioQuality(5)
}
return _ffmpeg.audioBitrate(_bitrate)
}

28
server/initializers/checker.ts
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@ -84,11 +84,11 @@ function checkMissedConfig () {
async function checkFFmpeg (CONFIG: { TRANSCODING: { ENABLED: boolean } }) {
const Ffmpeg = require('fluent-ffmpeg')
const getAvailableCodecsPromise = promisify0(Ffmpeg.getAvailableCodecs)
const codecs = await getAvailableCodecsPromise()
const canEncode = [ 'libx264' ]
if (CONFIG.TRANSCODING.ENABLED === false) return undefined
const canEncode = [ 'libx264' ]
for (const codec of canEncode) {
if (codecs[codec] === undefined) {
throw new Error('Unknown codec ' + codec + ' in FFmpeg.')
@ -98,6 +98,29 @@ async function checkFFmpeg (CONFIG: { TRANSCODING: { ENABLED: boolean } }) {
throw new Error('Unavailable encode codec ' + codec + ' in FFmpeg')
}
}
checkFFmpegEncoders()
}
// Optional encoders, if present, can be used to improve transcoding
// Here we ask ffmpeg if it detects their presence on the system, so that we can later use them
let supportedOptionalEncoders: Map<string, boolean>
async function checkFFmpegEncoders (): Promise<Map<string, boolean>> {
if (supportedOptionalEncoders !== undefined) {
return supportedOptionalEncoders
}
const Ffmpeg = require('fluent-ffmpeg')
const getAvailableEncodersPromise = promisify0(Ffmpeg.getAvailableEncoders)
const encoders = await getAvailableEncodersPromise()
const optionalEncoders = [ 'libfdk_aac' ]
supportedOptionalEncoders = new Map<string, boolean>()
for (const encoder of optionalEncoders) {
supportedOptionalEncoders.set(encoder,
encoders[encoder] !== undefined
)
}
}
// We get db by param to not import it in this file (import orders)
@ -126,6 +149,7 @@ async function applicationExist () {
export {
checkConfig,
checkFFmpeg,
checkFFmpegEncoders,
checkMissedConfig,
clientsExist,
usersExist,

16
server/tests/api/videos/multiple-servers.ts
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@ -209,19 +209,19 @@ describe('Test multiple servers', function () {
files: [
{
resolution: 240,
size: 190000
size: 100000
},
{
resolution: 360,
size: 280000
size: 180000
},
{
resolution: 480,
size: 390000
size: 280000
},
{
resolution: 720,
size: 710000
size: 630000
}
],
thumbnailfile: 'thumbnail',
@ -975,19 +975,19 @@ describe('Test multiple servers', function () {
files: [
{
resolution: 720,
size: 40315
size: 31000
},
{
resolution: 480,
size: 22808
size: 16000
},
{
resolution: 360,
size: 18617
size: 12000
},
{
resolution: 240,
size: 15217
size: 10000
}
]
}

4
server/tests/utils/videos/videos.ts
View File

@ -522,7 +522,9 @@ async function completeVideoCheck (
const minSize = attributeFile.size - ((10 * attributeFile.size) / 100)
const maxSize = attributeFile.size + ((10 * attributeFile.size) / 100)
expect(file.size).to.be.above(minSize).and.below(maxSize)
expect(file.size,
'File size for resolution ' + file.resolution.label + ' outside confidence interval.')
.to.be.above(minSize).and.below(maxSize)
{
await testImage(url, attributes.thumbnailfile || attributes.fixture, videoDetails.thumbnailPath)