[FFmpeg-user] Spontaneously slipping into command mode

[Jim DeLaHunt]

On 2025-07-27 15:45, Mark Filipak wrote:

> On 27/07/2025 16.51, Jim DeLaHunt wrote:
>> ...I understand that FFmpeg routinely monitors stdin while running...
> Oh, yes, of course. But-- But-- But my understanding is that > redirects
> to stdout.
>
> I'm not sending anything to stdin. ...So, (?).

You are not sending anything to FFmpeg's stdin in your commands. It 
certainly seems like FFmpeg is receiving something on its stdin. So, 
perhaps something else is sending something to FFmpeg's stdin?  Another 
agent in this situation is the Windows command shell, perhaps it is sending?

But understanding the root cause is one thing. Preventing the symptoms 
is another, but perhaps that is enough.  Does adding

    -nostdin

to your FFmpeg invocations prevent the problem?