frame offset + num frames to utilize http range header

[mogwai]

🚀 The feature

If load is called with a url e.g.

torchaudio.load(url, frame_offset=16000, num_frames=16000)

And the url supports range headers, is it not possible to only get the required bytes from the url??

Motivation, pitch

Would make it possible to load sections of large audio files quickly without having to pre cut them.

[ae99]

When using FFMPEG backend (and passing a URL or FileLike) and interacting with the underlying StreamingMediaDecoder, FFMPEG only ends up reading first n bytes to get num_frames. As far I can tell it also can use range requests on the underlying URL if it knows the framelength or has an index, but most variable bitrate formats it ends up just manually seeking.