[FFmpeg-user] Convert a file being downloaded

[LongkerDandy]

Hi

I'm tring to convert a file using command like:
ffmpeg -i input.mp4 -vcodec copy -acodec libfaac -ac 2 output.mp4

The problem is the file is being donwloaded and its size is keep increasing.
The ffmpeg conversion stopped long before the download finished.
So I only got part of the file.
Is there a good way to get around it?

In fact, I'm trying to convert some online videos.
I know ffmpeg can handle http and other protocols.
But I have to download it first because some website require special user
agent (or other http header).
So ffmpeg can't read them directly (at least I don't know how to change the
ffmpeg's http header).

Any hint?

Regards
LongkerDandy