.. _ffmpeg_cmds:

ffmpeg Commands
===============

Here is a collection of useful `ffmpeg <https://www.ffmpeg.org/>`_ commands for
converting image stacks to mp4s.

The basic command should look like this:

.. code:: shell

  ffmpeg -i frame_%5d.png -vcodec libx264 -pix_fmt yuv420p out.mp4

Where ``-i frame_%5d.png`` specifies the file pattern for the image stack. In
this case the files have a 5 digit integer padded with zeros
(i.e frame_00000.png, frame_00001.png, frame_00002.png, ...).

The ``-vcodec libx264`` specifies the use of the H264 codec, and the
``-pix_fmt yuv420p`` specifies the pixel format.

Finally, ``out.mp4`` specifies the output file name and mp4 container.

Other common flags that can be used to modify the resulting video are:

+-------------------+----------------------------------------------------------+
| Command           | Description                                              |
+===================+==========================================================+
| -r 60             | set the frame rate, in this case to 60 frames per second |
+-------------------+----------------------------------------------------------+
| -vf "transpose=1" | where the transpose parameter can be:                    |
|                   |                                                          |
|                   | * 0 = 90 Counter-clockwise and Vertical Flip (default)   |
|                   | * 1 = 90 Clockwise                                       |
|                   | * 2 = 90 Counter-clockwise                               |
|                   | * 3 = 90 Clockwise and Vertical Flip                     |
+-------------------+----------------------------------------------------------+
| -crf 25           | quality for constant quality mode, higher the number the |
|                   | smaller lower quality video.                             |
+-------------------+----------------------------------------------------------+

putting it all together:

.. code:: shell

  ffmpeg -r 20 -i frame_%5d.png -vf "transpose=1" -vcodec libx264 -pix_fmt yuv420p -crf 20 out.mp4