hajicj
commented
6 years ago Implicit triplet solutions are difficult in general, because they rely on musical patterns. Writers omit the triplet if it is "obvious" that there should be one, mostly in repeated patterns, but it is not clear what qualifies as a repeated pattern.
However, we can at least implement some special cases, like beamed groups of three. (Does NOT include groups interrupted by rests...)
The following algorithm should work after duration inference if a time signature is available:
0) Preprocessing.
- Create measures.
- Assign noteheads and rests to measures.
1) Find measures with duration discrepancies.
- Compute durations of all measures from the duration-bearing objects in the measure.
- Using time signatures, get the target durations of the measures.
- Mark measures where the computed duration does not fit with the target duration.
2) Find implicit triplet candidates.
- Find all beamed groups of three consecutive equal-duration notes & assign them to measures. The beamed group may be a sub-group, like the middle three 16ths in 8-16-16-16-8 (happens on page 1).
3) Decide which candidates to mark as implicit triplets.
- For each measure, try out shortening subsets of these groups to 2/3rds of their compound duration to see if they fit into the measure.
- If there is more than one option, shorten late.
There are implicit triplets in page 15...