[FFmpeg-user] Stream diferent window of panoramic video

[Moritz Barsnick]

On Wed, Aug 19, 2015 at 10:29:20 +0200, Marc Camacho Cateura wrote:
> Is exist a way to cut the video and stream only a window that change the
> position? I need a way to tell the ffmpeg what zone I want in realtime...
> Like paramterization of coordinates to crop?

If you know beforehand what to change, you can use expressions as
parameters to the crop filter. Although I can't get it to work right now,
the syntax would be:

  -vf "crop=if(gte(t\,10)\,200\,100):if(gte(t\,20)\,100\,50)"

(At 10 seconds, the width changes from 100 to 200. At 20 seconds, the
height changes from 50 to 100.)

As you mention "realtime": The zmq filter can dynamically receive
commands to change parameters of other filters:

  -vf "crop=640:480:100:100,zmq"

You then need to send commands to the zmq server with a tool like
zmqsend:

$ echo Parsed_crop_0 out_h 400 | tools/zmqsend
$ echo Parsed_crop_0 x 150 | tools/zmqsend
$ echo Parsed_crop_0 y 200 | tools/zmqsend

These examples change the crop filter's parameters out_h, x, y,
respectively.

(I haven't found a lot of documentation on this, unfortunately. For
example, I haven't figured out how to change two parameters at the same
time.)

Moritz

P.S.: ffmpeg needs to be compiled with zmq support for this filter to
      be available.