Should the following note appear in Set Format? I don't see it.
No, it just code comment
you can put anything between /* and */ as human-readable note to future self (or anyone reading the file)
+/* W Ratio, H Ratio
+Sets the ratio of the new canvas size (W, H) to the old (previous)
canvas size (W, H).
+The new canvas size is recalculated based upon a certain factor in the W Ratio,
+H Ratio fields. A practical use-case: The current resolution is
640x480, and for some reason
+you want it to be 1.33 times wider. You don't have to calculate what
640x1.33 is;
+you type 1.33 into the "W" input instead, and Cinelerra calculates it
for you. */
I don't understand what 1024*1024 means. I don't seem to notice any variation.
there is function av_reduce, in patch. You can see its last argument expressed as 1024*1024 - probably good for more exact result, but as Phyllis noticed can produce some ratios (m:n) we never saw before :)