This function is the same as gst_tividdec2_set_source_caps(), but takes
width, height, and colorspace as arguments instead of extracting these values
from the metedata of a DMAI buffer. gst_tividdec2_set_source_caps() now
gst_tividdec2_set_source_caps_base() with the values from the DMAI metadata.
The motivation for this is a set-up step for future work, and IMHO it is good
for these functions to have a version that is de-coupled from DMAI where