ffmpeg libraries now must be installed, breaking on users machines

[jonahclarsen]

🚀 The feature

I would love to see the continued support of the soundfile backend.

Motivation, pitch

Since 2.9.0 and the removal of the soundfile backend, this library doesn't work without torchcodec, which depends on ffmpeg dynamic libraries being discoverable on the users' machine. So if we update torchaudio from 2.8.0 to 2.9.0 in our program and release it to users, if they don't have ffmpeg libraries discoverable via PATH, it will break.

Alternatives

It's theoretically possible to install dynamic ffmpeg libraries on users' systems so that torch can find them, but a lot can go wrong. soundfile was a much simpler solution with less room for problems when distributing an app that depends on torchaudio.

Additional context

No response

[pearu]

soundfile backend was removed in #4041 per #3902, so this issue is not actionable.

The suggested alternative sounds like a reasonable approach.