[FFmpeg-user] Transcoding a file that is still being saved

[Maxim E]

Hi,

I'm trying to transcode a file that is still being saved.

Command :
ffmpeg -re -ss 00:01:00.00 -i file.mp4 -acodec libvorbis -ab 64k -vcodec
libvpx -vb 448k -f webm http://localhost:554/stream/

Current behavior : ffmpeg retrieves the duration when the command is
launched (for instance, " Duration: 00:01:42.78"). Everything will be done
correctly for 42 seconds (notice the "-ss 00:01:00.00" in my command),
however, ffmpeg won't notice the filesize / media duration has grown
meanwhile and will stop here. It basically considers the file's state to be
the same as at the beginning of the command.

Expected behavior : ffmpeg to keep transcoding the file until it reaches
the *real* end of the file.

This would be easy to do if I were using pipes, but I wouldn't be able to
seek then (which is mandatory for me).

Is there any way to achieve what I'm trying to do ?

Thanks for your help !