VP8 codec not supported for mp4 videos with ffmpeg?

[najwalb]

I am trying to generate an mp4 video with vp8 codec, and I get the following error:

OSError: [Errno 32] Broken pipe

FFMPEG COMMAND:
ffmpeg -y -f rawvideo -vcodec rawvideo -s 2000x700 -pix_fmt rgba -r 1.00 -i - -an -vcodec vp8 -pix_fmt yuv420p -qscale:v 1 -v warning -vf crop=trunc(iw/2)*2:trunc(ih/2)*2 my_path/test.mp4

FFMPEG STDERR OUTPUT:

Here is a minimal working example:

    paths = [] # add paths to the image frames
    chain = 0
    imgio_kargs = {'fps': 1, 'quality': 10, 'macro_block_size': None,
                    'codec': 'h264',
                   'ffmpeg_params': ['-vf', 'crop=trunc(iw/2)*2:trunc(ih/2)*2']}
    writer = imageio.get_writer('test.mp4', **imgio_kargs)
    for path in paths:
        img = imageio.v2.imread(path)
        writer.append_data(img)
    writer.close()

codecs that worked include vp9 and h264. I am just trying to understand why vp8 would not work when it's supported by ffmpeg normally: http://ffmpeg.org/ffmpeg-codecs.html (including in my own build version, which I can see by running: ffmpeg -codecs).