add more test case

[lucemia]

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https://github.com/kkroening/ffmpeg-python/blob/master/ffmpeg/tests/test_ffmpeg.py

https://github.com/kkroening/ffmpeg-python/blob/master/ffmpeg/tests/test_ffmpeg.py

• ffmpeg-python
• Python bindings for FFmpeg - with complex filtering support - ffmpeg-python/ffmpeg/tests/test_ffmpeg.py at master · kkroening/ffmpeg-python