[FFmpeg-user] Overlay one subtitle stream and copy another

Carl Eugen Hoyos cehoyos at ag.or.at
Tue Mar 8 02:42:39 CET 2016

Hans Carlson <forbyta <at> inbox.com> writes:

> In fact, it appears the fifo for the subtitle stream isn't 
> needed, because this works as well:
>    '[0:v]fifo[vid];[vid][0:3]overlay`

Yes, I thought so.

> My test file is only 22 secs long... is there a chance I'd 
> need the fifo on the subtitle stream if I'm processing 
> something longer?

Sorry, I don't know;-(
(But it should be trivial to test.)

> I'm not really sure what the fifo filter is doing or why 
> it's needed, 

I suspect it is related to the fact that not all parts of 
the pipeline operate with the same speed (or that some parts 
are too greedy), in any case, fifo is buffering frames so 
they don't get lost.

Carl Eugen

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