307 ffmpeg errors

[keighrim]

(partially) addresses #307 .

[codecov]

Codecov Report

Attention: Patch coverage is 70.58824% with 10 lines in your changes missing coverage. Please review.

Project coverage is 92.30%. Comparing base (364af05) to head (1688804).

Files with missing lines	Patch %	Lines
mmif/utils/video_document_helper.py	70.58%	10 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #308      +/-   ##
===========================================
- Coverage    92.50%   92.30%   -0.20%     
===========================================
  Files           10       10              
  Lines         1400     1416      +16     
===========================================
+ Hits          1295     1307      +12     
- Misses         105      109       +4     

Flag	Coverage Δ
unittests	92.30% <70.58%> (-0.20%)	⬇️

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