[FFmpeg-user] Using the flags -movflags +faststart

[Moritz Barsnick]

On Fri, Feb 24, 2017 at 19:36:05 -0700, JD wrote:
> I did not stop the encoding.
> Just opened another gnome-terminal and cd'd to the directory and
> tried to play the unfinished file.
> But now I see that I should not have included the + sign for the
> faststart.

The '+' doesn't matter.

You're misunderstanding what effect this flag: *After* completion of
encoding, ffmpeg will move the MOOV atom to the beginning of the file,
in order to allow faster playback ("faster" as in: the player doesn't
need to seek to the very end of the file first, in order to be able to
play it from beginning).

I doubt that MP4 files can *at all* be written so that they can be read
while still encoding. My understanding is: No, that will never work.
The format is just not suitable for that. You will want to use
something else like HLS/fragments, Matroska or so, and if needed remux
the file to MP4 later, when encoding is finished.

Moritz