Is there a recommended max size for files and images?

[Keeso]

I’m working on making a discussion forum for sharing music and samples and such. I haven’t decided yet if i’m going with something like 23 buckets for storing files or locally. In the beginning locally is probably easier and i can switch to s3 buckets if the site grows. But i was wondering if i should set a limit on file size. Any recommendations or thoughts are appreciated!  

[Dan Q]

Fortunately, you're equipped to do the maths on this one, because of how we measure the compression levels of common audio formats!

Take the longest audio file you'd expect to permit. E.g. maybe you don't anticipate anybody wanting to upload anything over 6 minutes, i.e. 360 seconds.

Take the maximum bitrate you'd expect to tolerate. For spoken-word, 96kbps MP3s (or lower) are usually fine, but for higher-fidelity music and samples you might be looking at e.g. 256kbps. If you need to, re-encode some of your music in a few different compression levels and see when you can tell the difference, then assume that some of your users have slightly more "golden ears" than you and step up a level. Let's say you chose e.g. 256kbps.

Multiply those two numbers together, then divide by 8 to get the expected kilobyte file size (after metadata, but that's pretty small!) of such a file; then divide by 1024 to get that in megabytes. So if somebody uploaded a 6 minute MP3 at 256kbps we'd expect it to weigh in at a hair over 360 × 256 / 8 / 1024 = 11.25Mb. Anything shorter or lower-quality (or both) than those two limits would be a smaller file size, so that'd be your upper limit.

[Keeso]

Wow thank you! I don’t quite understand why you divide by 8 but now i have a formula to go by anyway so thank you :seal