Source: streamingFileMeta.js

  1. /**
  2.  * Reads and serve video and audio files meta information.
  3.  */
  5. import fs from 'fs'
  6. import videoDuration from "get-video-duration"
  7. import mime from 'mime-types'
  9. const { getVideoDurationInSeconds } = videoDuration
  11. const fileMeta = new Map // filePath => metaObject
  12. var metaRead // a promise indicating if meta of all files has been read
  14. /**
  15.  * Get cached file meta info. Includes following properties:
  16.  * seconds, fullPath, type, mime, fileSize and pricePerByte.
  17.  * @param {string} fileName - file name
  18.  */
  19. export async function getMeta(fileName) {
  20.   if (!metaRead)
  21.     throw Error("call initMeta before calling getMeta")
  22.   await metaRead
  23.   return fileMeta.get(fileName)
  24. }
  26. /**
  27.  * Reads all media files in *mediaPath* and caches their meta information,
  28.  * such has fileSize, media length in seconds, pricePerByte, etc.
  29.  * @param {string} mediaPath path to folder where media files are stored.
  30.  * @param {object} config including *pricePerMinute* or *pricePerMB* property.
  31.  * @returns Promise indicating if meta information has been read.
  32.  */
  33. export function initStreamingMeta(mediaPath, config) {
  34.   metaRead = readMeta(mediaPath, config)
  35. }
  37. // TODO: read all videos in given folder - now just 'videoPath'
  38. async function readMeta(mediaPath, config) {
  39.   validateConfig(config)
  40.   const files = await fs.promises.readdir(mediaPath)
  41.   const allRead = files.map(async function(file) {
  42.     if (file.slice(0,1) == '.')
  43.       return // skip .DS_Store etc
  44.     const fullMediaPath = mediaPath + file
  45.     const stats = await fs.promises.stat(fullMediaPath)
  46.     const seconds = await getVideoDurationInSeconds(fullMediaPath)
  47.     const type = file.split('.')[1],  // e.g. 'mp4'
  48.           meta = {
  49.             seconds,
  50.             fullPath: fullMediaPath,
  51.             type: type,
  52.             mime: mime.lookup(type),
  53.             fileSize: stats.size,
  54.             pricePerByte: pricePerByte(seconds, stats.size, config),
  55.           }
  56.     fileMeta.set(file, meta)
  57.   })
  58.   await Promise.all(allRead)
  59. }
  61. function pricePerByte(seconds, fileSize,
  62.                       {pricePerMB, pricePerMinute}) {
  63.   if (pricePerMB)
  64.     return pricePerMB / 10**6
  65.   if (!pricePerMinute)
  66.     throw Error("pricePerMinute or pricePerMB required in configs")
  68.   const pricePerSecond = pricePerMinute/60,
  69.         bytesInSecond = fileSize / seconds,
  70.         pricePerByte = pricePerSecond / bytesInSecond
  71.   return pricePerByte
  72. }
  74. function validateConfig({pricePerMB, pricePerMinute}) {
  75.   if (pricePerMB && pricePerMinute)
  76.     throw Error("Price can be defined only in minutes or in megabytes, set the other one as null.")
  77. }