Set the index interval range to check when looking for the first image
file in the sequence, starting from @var{start_number}. Default value
is 5.
+@item ts_from_file
+If set to 1, will set frame timestamp to modification time of image file. Note
+that monotonity of timestamps is not provided: images go in the same order as
+without this option. Default value is 0.
@item video_size
Set the video size of the images to read. If not specified the video
size is guessed from the first image file in the sequence.