Hey everyone!

I need advice on resampling.

To give you context, I am working at SoundCloud, and one of the current projects is to refactor the transcoding pipeline. And proper resampling tools is a question that keeps coming up.

One of the pipelines takes the uploaded file and transcodes it into an mp3. The general idea is to convert the original file to wav, resample it to 44100, and then finally convert it to mp3 using LAME.

There are several questions here.

1. Which tool to use for transcoding. Should it be SoX, or FFmpeg, or something else? A lot of the info out there seems to favor SoX, but a lot of that info is pretty old.

2. Does it make sense to resample to 44100 or to 48000? If it were opus, the answer if simple: 48000, because that's what the opus spec actually recommends. There is no such recommendation for mp3 files. Also, upsampling is not an innocent procedure and the converter has to be of high quality as well.

p.s.: the described pipeline is not the only one, the original file is transcoded into multiple formats, including formats with 48000 sample rate, but the one I am asking about focuses specifically on producing an mp3.