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-rw-r--r--server/helpers/ffmpeg-utils.ts121
1 files changed, 116 insertions, 5 deletions
diff --git a/server/helpers/ffmpeg-utils.ts b/server/helpers/ffmpeg-utils.ts
index f0623c88b..eb1c86ab9 100644
--- a/server/helpers/ffmpeg-utils.ts
+++ b/server/helpers/ffmpeg-utils.ts
@@ -5,6 +5,7 @@ import { CONFIG, VIDEO_TRANSCODING_FPS } from '../initializers'
5import { unlinkPromise } from './core-utils' 5import { unlinkPromise } from './core-utils'
6import { processImage } from './image-utils' 6import { processImage } from './image-utils'
7import { logger } from './logger' 7import { logger } from './logger'
8import { checkFFmpegEncoders } from '../initializers/checker'
8 9
9async function getVideoFileResolution (path: string) { 10async function getVideoFileResolution (path: string) {
10 const videoStream = await getVideoFileStream(path) 11 const videoStream = await getVideoFileStream(path)
@@ -85,12 +86,8 @@ function transcode (options: TranscodeOptions) {
85 return new Promise<void>(async (res, rej) => { 86 return new Promise<void>(async (res, rej) => {
86 let command = ffmpeg(options.inputPath) 87 let command = ffmpeg(options.inputPath)
87 .output(options.outputPath) 88 .output(options.outputPath)
88 .videoCodec('libx264')
89 .outputOption('-threads ' + CONFIG.TRANSCODING.THREADS) 89 .outputOption('-threads ' + CONFIG.TRANSCODING.THREADS)
90 .outputOption('-movflags faststart') 90 .preset(standard)
91 .outputOption('-b_strategy 1') // NOTE: b-strategy 1 - heuristic algorythm, 16 is optimal B-frames for it
92 .outputOption('-bf 16') // NOTE: Why 16: https://github.com/Chocobozzz/PeerTube/pull/774. b-strategy 2 -> B-frames<16
93 // .outputOption('-crf 18')
94 91
95 let fps = await getVideoFileFPS(options.inputPath) 92 let fps = await getVideoFileFPS(options.inputPath)
96 if (options.resolution !== undefined) { 93 if (options.resolution !== undefined) {
@@ -149,3 +146,117 @@ function getVideoFileStream (path: string) {
149 }) 146 })
150 }) 147 })
151} 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 */
157function 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 */
178function audio (ffmpeg) {
179 ffmpeg
180 .preset(veryfast)
181 .outputOption('-tune stillimage')
182}
183
184/**
185 * A toolbox to play with audio
186 */
187namespace 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 */
232async 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}