FFMPEG (libx264) “height not divisible by 2”

Question

I am trying to encode a .mp4 video from a set of frames using FFMPEG using the libx264 codec.

This is the command I am running:

/usr/local/bin/ffmpeg -r 24 -i frame_%05d.jpg -vcodec libx264 -y -an video.mp4

I sometimes get the following error:

[libx264 @ 0xa3b85a0] height not divisible by 2 (520x369)

After searching around a bit it seems that the issue has something to do with the scaling algorithm and can be fixed by adding a -vf argument.

However, in my case I don't want to do any scaling. Ideally, I want to keep the dimensions exactly the same as the frames. Any advice? Is there some sort of aspect ratio that h264 enforces?

Answer 1

The problem with the scale solutions here is that they distort the source image/video which is almost never what you want.

Instead, I've found the best solution is to add a 1-pixel pad to the odd dimension. (By default, the pading is black and hard to notice.)

The problem with the other pad solutions is that they do not generalize over arbitrary dimensions because they always pad.

This solution only adds a 1-pixel pad to height and/or width if they are odd:

-vf pad="width=ceil(iw/2)*2:height=ceil(ih/2)*2"

This is ideal because it always does the right thing even when no padding is necessary.