[BUG] Hybrid cannot differentiate between image sequences in a directory

[mantom]

I should add - this also applies to situations where an individual sequence numbering is interrupted, but not used.

for example, you have the following image sequence:

image_0001.png
image_0002.png
image_0003.png
...
image_1000.png

but image_0500.png through image_0700.png are missing, and you want to encode frames 0001 through 0400.  Hybrid complains the image sequence is bad even though the missing frames are outside the range being used as input.