X-Git-Url: https://git.immae.eu/?a=blobdiff_plain;f=server%2Fhelpers%2Fffmpeg-utils.ts;h=df3926658d54594b60056936e6a75717c9e9889c;hb=daf6e4801052d3ca6be2fafd20bae2323b1ce175;hp=c7296054daa6c365af98f2f287322921203b8d9b;hpb=9ecac97be024cf2277872986950d7eec85cbc76e;p=github%2FChocobozzz%2FPeerTube.git diff --git a/server/helpers/ffmpeg-utils.ts b/server/helpers/ffmpeg-utils.ts index c7296054d..df3926658 100644 --- a/server/helpers/ffmpeg-utils.ts +++ b/server/helpers/ffmpeg-utils.ts @@ -1,79 +1,13 @@ import * as ffmpeg from 'fluent-ffmpeg' -import { join } from 'path' +import { readFile, remove, writeFile } from 'fs-extra' +import { dirname, join } from 'path' import { getTargetBitrate, VideoResolution } from '../../shared/models/videos' -import { CONFIG, FFMPEG_NICE, VIDEO_TRANSCODING_FPS } from '../initializers/constants' +import { checkFFmpegEncoders } from '../initializers/checker-before-init' +import { CONFIG } from '../initializers/config' +import { FFMPEG_NICE, VIDEO_LIVE, VIDEO_TRANSCODING_FPS } from '../initializers/constants' +import { getAudioStream, getClosestFramerateStandard, getMaxAudioBitrate, getVideoFileFPS } from './ffprobe-utils' import { processImage } from './image-utils' import { logger } from './logger' -import { checkFFmpegEncoders } from '../initializers/checker-before-init' -import { remove } from 'fs-extra' - -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 -} - -async function getVideoFileResolution (path: string) { - const videoStream = await getVideoFileStream(path) - - return { - videoFileResolution: Math.min(videoStream.height, videoStream.width), - isPortraitMode: videoStream.height > videoStream.width - } -} - -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) - } - - return 0 -} - -async function getVideoFileBitrate (path: string) { - return new Promise((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((res, rej) => { - ffmpeg.ffprobe(path, (err, metadata) => { - if (err) return rej(err) - - return res(Math.floor(metadata.format.duration)) - }) - }) -} async function generateImageFromVideoFile (fromPath: string, folder: string, imageName: string, size: { width: number, height: number }) { const pendingImageName = 'pending-' + imageName @@ -95,7 +29,7 @@ async function generateImageFromVideoFile (fromPath: string, folder: string, ima }) const destination = join(folder, imageName) - await processImage({ path: pendingImagePath }, destination, size) + await processImage(pendingImagePath, destination, size) } catch (err) { logger.error('Cannot generate image from video %s.', fromPath, { err }) @@ -107,88 +41,372 @@ async function generateImageFromVideoFile (fromPath: string, folder: string, ima } } -type TranscodeOptions = { +// --------------------------------------------------------------------------- +// Transcode meta function +// --------------------------------------------------------------------------- + +type TranscodeOptionsType = 'hls' | 'quick-transcode' | 'video' | 'merge-audio' | 'only-audio' + +interface BaseTranscodeOptions { + type: TranscodeOptionsType inputPath: string outputPath: string - resolution?: VideoResolution + resolution: VideoResolution isPortraitMode?: boolean } -function transcode (options: TranscodeOptions) { +interface HLSTranscodeOptions extends BaseTranscodeOptions { + type: 'hls' + copyCodecs: boolean + hlsPlaylist: { + videoFilename: string + } +} + +interface QuickTranscodeOptions extends BaseTranscodeOptions { + type: 'quick-transcode' +} + +interface VideoTranscodeOptions extends BaseTranscodeOptions { + type: 'video' +} + +interface MergeAudioTranscodeOptions extends BaseTranscodeOptions { + type: 'merge-audio' + audioPath: string +} + +interface OnlyAudioTranscodeOptions extends BaseTranscodeOptions { + type: 'only-audio' +} + +type TranscodeOptions = + HLSTranscodeOptions + | VideoTranscodeOptions + | MergeAudioTranscodeOptions + | OnlyAudioTranscodeOptions + | QuickTranscodeOptions + +const builders: { + [ type in TranscodeOptionsType ]: (c: ffmpeg.FfmpegCommand, o?: TranscodeOptions) => Promise | ffmpeg.FfmpegCommand +} = { + 'quick-transcode': buildQuickTranscodeCommand, + 'hls': buildHLSVODCommand, + 'merge-audio': buildAudioMergeCommand, + 'only-audio': buildOnlyAudioCommand, + 'video': buildx264Command +} + +async function transcode (options: TranscodeOptions) { + logger.debug('Will run transcode.', { options }) + + let command = getFFmpeg(options.inputPath) + .output(options.outputPath) + + command = await builders[options.type](command, options) + + await runCommand(command) + + await fixHLSPlaylistIfNeeded(options) +} + +function convertWebPToJPG (path: string, destination: string): Promise { + return new Promise(async (res, rej) => { + try { + const command = ffmpeg(path).output(destination) + + command.on('error', (err, stdout, stderr) => { + logger.error('Error in ffmpeg webp convert process.', { stdout, stderr }) + return rej(err) + }) + .on('end', () => res()) + .run() + } catch (err) { + return rej(err) + } + }) +} + +function processGIF ( + path: string, + destination: string, + newSize: { width: number, height: number }, + keepOriginal = false +): Promise { return new Promise(async (res, rej) => { + if (path === destination) { + throw new Error('FFmpeg needs an input path different that the output path.') + } + + logger.debug('Processing gif %s to %s.', path, destination) + try { - let fps = await getVideoFileFPS(options.inputPath) - // On small/medium resolutions, limit FPS - if ( - options.resolution !== undefined && - options.resolution < VIDEO_TRANSCODING_FPS.KEEP_ORIGIN_FPS_RESOLUTION_MIN && - fps > VIDEO_TRANSCODING_FPS.AVERAGE - ) { - fps = VIDEO_TRANSCODING_FPS.AVERAGE - } - - let command = ffmpeg(options.inputPath, { niceness: FFMPEG_NICE.TRANSCODING }) - .output(options.outputPath) - command = await presetH264(command, options.resolution, fps) - - if (CONFIG.TRANSCODING.THREADS > 0) { - // if we don't set any threads ffmpeg will chose automatically - command = command.outputOption('-threads ' + CONFIG.TRANSCODING.THREADS) - } - - if (options.resolution !== undefined) { - // '?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) - } - - command - .on('error', (err, stdout, stderr) => { - logger.error('Error in transcoding job.', { stdout, stderr }) - return rej(err) - }) - .on('end', res) - .run() + const command = ffmpeg(path) + .fps(20) + .size(`${newSize.width}x${newSize.height}`) + .output(destination) + + command.on('error', (err, stdout, stderr) => { + logger.error('Error in ffmpeg gif resizing process.', { stdout, stderr }) + return rej(err) + }) + .on('end', async () => { + if (keepOriginal !== true) await remove(path) + res() + }) + .run() } catch (err) { return rej(err) } }) } +function runLiveTranscoding (rtmpUrl: string, outPath: string, resolutions: number[], fps, deleteSegments: boolean) { + const command = getFFmpeg(rtmpUrl) + command.inputOption('-fflags nobuffer') + + const varStreamMap: string[] = [] + + command.complexFilter([ + { + inputs: '[v:0]', + filter: 'split', + options: resolutions.length, + outputs: resolutions.map(r => `vtemp${r}`) + }, + + ...resolutions.map(r => ({ + inputs: `vtemp${r}`, + filter: 'scale', + options: `w=-2:h=${r}`, + outputs: `vout${r}` + })) + ]) + + command.outputOption('-b_strategy 1') + command.outputOption('-bf 16') + command.outputOption('-preset superfast') + command.outputOption('-level 3.1') + command.outputOption('-map_metadata -1') + command.outputOption('-pix_fmt yuv420p') + command.outputOption('-max_muxing_queue_size 1024') + command.outputOption('-g ' + (fps * 2)) + + for (let i = 0; i < resolutions.length; i++) { + const resolution = resolutions[i] + + command.outputOption(`-map [vout${resolution}]`) + command.outputOption(`-c:v:${i} libx264`) + command.outputOption(`-b:v:${i} ${getTargetBitrate(resolution, fps, VIDEO_TRANSCODING_FPS)}`) + + command.outputOption(`-map a:0`) + command.outputOption(`-c:a:${i} aac`) + + varStreamMap.push(`v:${i},a:${i}`) + } + + addDefaultLiveHLSParams(command, outPath, deleteSegments) + + command.outputOption('-var_stream_map', varStreamMap.join(' ')) + + command.run() + + return command +} + +function runLiveMuxing (rtmpUrl: string, outPath: string, deleteSegments: boolean) { + const command = getFFmpeg(rtmpUrl) + command.inputOption('-fflags nobuffer') + + command.outputOption('-c:v copy') + command.outputOption('-c:a copy') + command.outputOption('-map 0:a?') + command.outputOption('-map 0:v?') + + addDefaultLiveHLSParams(command, outPath, deleteSegments) + + command.run() + + return command +} + +async function hlsPlaylistToFragmentedMP4 (hlsDirectory: string, segmentFiles: string[], outputPath: string) { + const concatFilePath = join(hlsDirectory, 'concat.txt') + + function cleaner () { + remove(concatFilePath) + .catch(err => logger.error('Cannot remove concat file in %s.', hlsDirectory, { err })) + } + + // First concat the ts files to a mp4 file + const content = segmentFiles.map(f => 'file ' + f) + .join('\n') + + await writeFile(concatFilePath, content + '\n') + + const command = getFFmpeg(concatFilePath) + command.inputOption('-safe 0') + command.inputOption('-f concat') + + command.outputOption('-c:v copy') + command.audioFilter('aresample=async=1:first_pts=0') + command.output(outputPath) + + return runCommand(command, cleaner) +} + +async function runCommand (command: ffmpeg.FfmpegCommand, onEnd?: Function) { + return new Promise((res, rej) => { + command.on('error', (err, stdout, stderr) => { + if (onEnd) onEnd() + + logger.error('Error in transcoding job.', { stdout, stderr }) + rej(err) + }) + + command.on('end', () => { + if (onEnd) onEnd() + + res() + }) + + command.run() + }) +} + // --------------------------------------------------------------------------- export { - getVideoFileResolution, - getDurationFromVideoFile, + runLiveMuxing, + convertWebPToJPG, + processGIF, + runLiveTranscoding, generateImageFromVideoFile, + TranscodeOptions, + TranscodeOptionsType, transcode, - getVideoFileFPS, - computeResolutionsToTranscode, - audio, - getVideoFileBitrate + hlsPlaylistToFragmentedMP4 } // --------------------------------------------------------------------------- -function getVideoFileStream (path: string) { - return new Promise((res, rej) => { - ffmpeg.ffprobe(path, (err, metadata) => { - if (err) return rej(err) +function addDefaultX264Params (command: ffmpeg.FfmpegCommand) { + command.outputOption('-level 3.1') // 3.1 is the minimal resource allocation for our highest supported resolution + .outputOption('-b_strategy 1') // NOTE: b-strategy 1 - heuristic algorithm, 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('-pix_fmt yuv420p') // allows import of source material with incompatible pixel formats (e.g. MJPEG video) + .outputOption('-map_metadata -1') // strip all metadata +} - const videoStream = metadata.streams.find(s => s.codec_type === 'video') - if (!videoStream) return rej(new Error('Cannot find video stream of ' + path)) +function addDefaultLiveHLSParams (command: ffmpeg.FfmpegCommand, outPath: string, deleteSegments: boolean) { + command.outputOption('-hls_time ' + VIDEO_LIVE.SEGMENT_TIME_SECONDS) + command.outputOption('-hls_list_size ' + VIDEO_LIVE.SEGMENTS_LIST_SIZE) - return res(videoStream) - }) - }) + if (deleteSegments === true) { + command.outputOption('-hls_flags delete_segments') + } + + command.outputOption(`-hls_segment_filename ${join(outPath, '%v-%06d.ts')}`) + command.outputOption('-master_pl_name master.m3u8') + command.outputOption(`-f hls`) + + command.output(join(outPath, '%v.m3u8')) +} + +async function buildx264Command (command: ffmpeg.FfmpegCommand, options: TranscodeOptions) { + let fps = await getVideoFileFPS(options.inputPath) + if ( + // On small/medium resolutions, limit FPS + options.resolution !== undefined && + options.resolution < VIDEO_TRANSCODING_FPS.KEEP_ORIGIN_FPS_RESOLUTION_MIN && + fps > VIDEO_TRANSCODING_FPS.AVERAGE + ) { + // Get closest standard framerate by modulo: downsampling has to be done to a divisor of the nominal fps value + fps = getClosestFramerateStandard(fps, 'STANDARD') + } + + command = await presetH264(command, options.inputPath, options.resolution, fps) + + if (options.resolution !== undefined) { + // '?x720' or '720x?' for example + const size = options.isPortraitMode === true ? `${options.resolution}x?` : `?x${options.resolution}` + command = command.size(size) + } + + if (fps) { + // Hard FPS limits + if (fps > VIDEO_TRANSCODING_FPS.MAX) fps = getClosestFramerateStandard(fps, 'HD_STANDARD') + else if (fps < VIDEO_TRANSCODING_FPS.MIN) fps = VIDEO_TRANSCODING_FPS.MIN + + command = command.withFPS(fps) + } + + return command +} + +async function buildAudioMergeCommand (command: ffmpeg.FfmpegCommand, options: MergeAudioTranscodeOptions) { + command = command.loop(undefined) + + command = await presetH264VeryFast(command, options.audioPath, options.resolution) + + command = command.input(options.audioPath) + .videoFilter('scale=trunc(iw/2)*2:trunc(ih/2)*2') // Avoid "height not divisible by 2" error + .outputOption('-tune stillimage') + .outputOption('-shortest') + + return command +} + +function buildOnlyAudioCommand (command: ffmpeg.FfmpegCommand, _options: OnlyAudioTranscodeOptions) { + command = presetOnlyAudio(command) + + return command +} + +function buildQuickTranscodeCommand (command: ffmpeg.FfmpegCommand) { + command = presetCopy(command) + + command = command.outputOption('-map_metadata -1') // strip all metadata + .outputOption('-movflags faststart') + + return command +} + +async function buildHLSVODCommand (command: ffmpeg.FfmpegCommand, options: HLSTranscodeOptions) { + const videoPath = getHLSVideoPath(options) + + if (options.copyCodecs) command = presetCopy(command) + else if (options.resolution === VideoResolution.H_NOVIDEO) command = presetOnlyAudio(command) + else command = await buildx264Command(command, options) + + command = command.outputOption('-hls_time 4') + .outputOption('-hls_list_size 0') + .outputOption('-hls_playlist_type vod') + .outputOption('-hls_segment_filename ' + videoPath) + .outputOption('-hls_segment_type fmp4') + .outputOption('-f hls') + .outputOption('-hls_flags single_file') + + return command +} + +function getHLSVideoPath (options: HLSTranscodeOptions) { + return `${dirname(options.outputPath)}/${options.hlsPlaylist.videoFilename}` +} + +async function fixHLSPlaylistIfNeeded (options: TranscodeOptions) { + if (options.type !== 'hls') return + + const fileContent = await readFile(options.outputPath) + + const videoFileName = options.hlsPlaylist.videoFilename + const videoFilePath = getHLSVideoPath(options) + + // Fix wrong mapping with some ffmpeg versions + const newContent = fileContent.toString() + .replace(`#EXT-X-MAP:URI="${videoFilePath}",`, `#EXT-X-MAP:URI="${videoFileName}",`) + + await writeFile(options.outputPath, newContent) } /** @@ -198,123 +416,37 @@ function getVideoFileStream (path: string) { * and quality. Superfast and ultrafast will give you better * performance, but then quality is noticeably worse. */ -async function presetH264VeryFast (command: ffmpeg.FfmpegCommand, resolution: VideoResolution, fps: number): Promise { - let localCommand = await presetH264(command, resolution, fps) +async function presetH264VeryFast (command: ffmpeg.FfmpegCommand, input: string, resolution: VideoResolution, fps?: number) { + let localCommand = await presetH264(command, input, resolution, fps) + localCommand = localCommand.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 + although 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. */ return localCommand } -/** - * A preset optimised for a stillimage audio video - */ -async function presetStillImageWithAudio ( - command: ffmpeg.FfmpegCommand, - resolution: VideoResolution, - fps: number -): Promise { - let localCommand = await presetH264VeryFast(command, resolution, fps) - localCommand = localCommand.outputOption('-tune stillimage') - - return localCommand -} - -/** - * A toolbox to play with audio - */ -namespace audio { - export const get = (option: ffmpeg.FfmpegCommand | string) => { - // 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 - return new Promise<{ absolutePath: string, audioStream?: any }>((res, rej) => { - - function parseFfprobe (err: any, data: ffmpeg.FfprobeData) { - 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 - }) - } - } - - return res({ absolutePath: data.format.filename }) - } - - if (typeof option === 'string') { - return ffmpeg.ffprobe(option, parseFfprobe) - } - - return option.ffprobe(parseFfprobe) - }) - } - - export namespace bitrate { - const baseKbitrate = 384 - - const toBits = (kbits: number): number => { return kbits * 8000 } - - export const aac = (bitrate: number): number => { - switch (true) { - 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 => { - /* - 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 (command: ffmpeg.FfmpegCommand, resolution: VideoResolution, fps: number): Promise { +async function presetH264 (command: ffmpeg.FfmpegCommand, input: string, resolution: VideoResolution, fps?: number) { let localCommand = command .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('-pix_fmt yuv420p') // allows import of source material with incompatible pixel formats (e.g. MJPEG video) - .outputOption('-map_metadata -1') // strip all metadata .outputOption('-movflags faststart') - const parsedAudio = await audio.get(localCommand) + addDefaultX264Params(localCommand) + + const parsedAudio = await getAudioStream(input) if (!parsedAudio.audioStream) { localCommand = localCommand.noAudio() @@ -323,28 +455,55 @@ async function presetH264 (command: ffmpeg.FfmpegCommand, resolution: VideoResol .audioCodec('libfdk_aac') .audioQuality(5) } else { - // we try to reduce the ceiling bitrate by making rough correspondances of bitrates + // we try to reduce the ceiling bitrate by making rough matches of bitrates // of course this is far from perfect, but it might save some space in the end - const audioCodecName = parsedAudio.audioStream[ 'codec_name' ] - let bitrate: number - if (audio.bitrate[ audioCodecName ]) { - localCommand = localCommand.audioCodec('aac') + localCommand = localCommand.audioCodec('aac') - bitrate = audio.bitrate[ audioCodecName ](parsedAudio.audioStream[ 'bit_rate' ]) - if (bitrate !== undefined && bitrate !== -1) localCommand = localCommand.audioBitrate(bitrate) - } - } + const audioCodecName = parsedAudio.audioStream['codec_name'] - // 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) - localCommand = localCommand.outputOptions([`-maxrate ${ targetBitrate }`, `-bufsize ${ targetBitrate * 2 }`]) + const bitrate = getMaxAudioBitrate(audioCodecName, parsedAudio.bitrate) - // 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 - localCommand = localCommand.outputOption(`-g ${ fps * 2 }`) + if (bitrate !== undefined && bitrate !== -1) localCommand = localCommand.audioBitrate(bitrate) + } + + if (fps) { + // 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) + localCommand = localCommand.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 + localCommand = localCommand.outputOption(`-g ${fps * 2}`) + } return localCommand } + +function presetCopy (command: ffmpeg.FfmpegCommand): ffmpeg.FfmpegCommand { + return command + .format('mp4') + .videoCodec('copy') + .audioCodec('copy') +} + +function presetOnlyAudio (command: ffmpeg.FfmpegCommand): ffmpeg.FfmpegCommand { + return command + .format('mp4') + .audioCodec('copy') + .noVideo() +} + +function getFFmpeg (input: string) { + // We set cwd explicitly because ffmpeg appears to create temporary files when trancoding which fails in read-only file systems + const command = ffmpeg(input, { niceness: FFMPEG_NICE.TRANSCODING, cwd: CONFIG.STORAGE.TMP_DIR }) + + if (CONFIG.TRANSCODING.THREADS > 0) { + // If we don't set any threads ffmpeg will chose automatically + command.outputOption('-threads ' + CONFIG.TRANSCODING.THREADS) + } + + return command +}