上传到Firebase存储时如何使用Cloud Functions for FIrebase获取mp3文件的持续时间

Question

I am in the process of building a music library for a dance app. Currently I have the Cloud Function automatically create an database instance when a mp3 file is uploaded to Firebase storage, I still need to fetch the duration of that mp3 file in seconds somehow and store that info in database. I am new to javascript and first time doing node.js, some sources point to using the mp3 metadata which I have no experience playing with either. Some help would be much appreciated.

Answer 1

The easiest way to do this would be have your cloud function download each MP3 file, open it via some MP3-reading library, and get the length using some library, like mp3-duration .

The main problem here is that downloading the entire MP3 just to calculate its duration is something of a waste of bandwidth. You could probably improve on that, but doing so would probably be somewhat complex unless MP3 files happen to conveniently list their duration somewhere in the header (which I don't think is the case, but I'm not very familiar with the format).

It might be better to have whatever tool is uploading the objects calculate the duration locally and then add a piece of custom metadata to the object being uploaded that indicates its duration. The custom metadata will be available to the cloud function, which can them make use of it.