Fix CompositeVideoClip mask [1, 1] unexpected shape - Issue #2247

[Implosiv3]

Fixes the issue when concatenating videoclips as mask is being considered as [1, 1] so the mask shape is different from the other videos and fails.

I think [1, 1] could be a default mask to avoid divisions by zero or something similar, but here it does not make sense.

Issue here: #2247

• I have provided code that clearly demonstrates the bug and that only works correctly when applying this fix
• I have added suitable tests demonstrating a fixed bug or new/changed feature to the test suite in tests/
• I have properly documented new or changed features in the documentation or in the docstrings
• I have properly explained unusual or unexpected code in the comments around it

[Zulko]

Thank you! Would you have time to add a minimal test? Some test snippet that would fail on the last release, but succeed with that change?

[Implosiv3]

Thank you! Would you have time to add a minimal test? Some test snippet that would fail on the last release, but succeed with that change?

If I try to execute this code below in which I try to concatenate one clip withou a mask and one with the default mask:

from moviepy import concatenate_videoclips, VideoFileClip

video_without_mask = VideoFileClip('prueba.mp4')
video_with_mask = VideoFileClip('prueba.mp4').with_mask()

concatenate_videoclips([video_without_mask, video_with_mask]).write_videofile('test.mp4')

This is the result I receive:

videos = concatenate_videos([
  File "<decorator-gen-68>", line 2, in write_videofile
  File "C:\Users\dania\AppData\Local\Programs\Python\Python39\lib\site-packages\moviepy\decorators.py", line 53, in requires_duration      
    return func(clip, *args, **kwargs)
  File "<decorator-gen-67>", line 2, in write_videofile
  File "C:\Users\dania\AppData\Local\Programs\Python\Python39\lib\site-packages\moviepy\decorators.py", line 143, in use_clip_fps_by_default
    return func(clip, *new_args, **new_kwargs)
  File "<decorator-gen-66>", line 2, in write_videofile
    return func(clip, *args, **kwargs)
  File "<decorator-gen-65>", line 2, in write_videofile
  File "C:\Users\dania\AppData\Local\Programs\Python\Python39\lib\site-packages\moviepy\decorators.py", line 94, in wrapper
    return func(*new_args, **new_kwargs)
  File "C:\Users\dania\AppData\Local\Programs\Python\Python39\lib\site-packages\moviepy\video\VideoClip.py", line 389, in write_videofile  
    ffmpeg_write_video(
  File "C:\Users\dania\AppData\Local\Programs\Python\Python39\lib\site-packages\moviepy\video\io\ffmpeg_writer.py", line 263, in ffmpeg_write_video
    frame = np.dstack([frame, mask])
  File "C:\Users\dania\AppData\Local\Programs\Python\Python39\lib\site-packages\numpy\lib\shape_base.py", line 715, in dstack
    return _nx.concatenate(arrs, 2)
ValueError: all the input array dimensions except for the concatenation axis must match exactly, but along dimension 0, the array at index 
0 has size 1080 and the array at index 1 has size 1

If you apply the change, it works:

MoviePy - Done.
MoviePy - Writing video test.mp4

frame_index:  45%|█████████████████████████████████▉                                          | 111/249 [00:13<00:14,  9.21it/s, now=

As the first clip doesn't have any mask, the system applies one [1, 1] shape ColorClip default mask, which is incompatible with the [1920, 1080] of the other clip.

[OsaAjani]

closed by #2307, thanks for pointing it out !