[FFmpeg-user] convert audio files to serve them on website

[David Froger]

I'm also planning to use the `-progress` option, to display a progress
bar to the uploader client.

Quoting David Froger (2021-01-20 00:03:20)
> Hello,
> 
> I'm building a website that allow talks to be uploaded (HTTPS POST)
> and then be streamed (html5 audio element) or downloaded (HTTPS GET).
> I'm also thinking to make them available as podcast. As I have no
> experience with audio files, I'm looking for advices.
> 
> I would like the upload/download/stream to be as portable as possible:
> Currently, the talks may be recorded for example from a voice record, a
> smartphone, a tablet. It is then directly uploaded to the website. I've
> encountered these formats: (.mp3, .m4a, .3gp) but I would like to
> support as much formats as possible. It may then be streamed or
> downloaded from one of the major desktop (GNU/Linux, OSX, Windows) or
> mobile/tablet (Androïd, IOS) browsers.
> 
> So I would like to convert the uploaded file with ffmpeg before serving
> it (done by the webserver).
> 
> Some questions I have:
> - Would .mp3 be the most appropriate format?
> - Should I adapt the ffmpeg command according to the input file, or can I use
>   an "universal command", something like: ffmpeg -i file.{.m4a,3gp,...} -vn file.mp3
> - Should I add "-acodec libmp3lame", or is it implicit from the output
>   file .mp3 extension?
> - Is there any benefit from adding other options? For example here
>   https://stackoverflow.com/a/12952172 I've seen "-ar 44100", but why
>   not just keep the input frequency? (same for "-ac 2" and "-b:a 192k",
>   why not just keep what is in the input, is it just to optimize the
>   size of the output file?) Any other useful option?
> 
> Thanks for reading!