Compressed version standard

[pythouille]

What are the specification for compressed / uncompressed? The aim is to keep only necessary information without any loss of information.

• First of all, a fully compressed version is also non-verbose (see non-verbose specification https://github.com/johentsch/specs/issues/2#issue-1907033350): the only values that are written are those that are different from the default values.
• If a measure can be entirely deduced from the previous one, then it does not appear in the compressed measure map. The following displayed measure must mention its number so that we can deduce how many measures were skipped this way.
• The last measure of the original measure map is always put in the compressed measure map -- with its 'number'.
  • (An alternative solutions have been proposed to indicate endings: an end-of-piece token with qstamp indicating the length of the piece in quarter notes (and 'count' -1 ?))

Remarks/questions:

• 1- We mentioned that having specific ID for each measure involves that they all need to be in the measure map (i.e. no compression possible). Should we discourage this practice, or accept to lose this information in some cases?
• We have a short compression example in the article [{'time_signature': 'cut'}, {'number': 563}]:
  • 2- Why do we put 'number' instead of 'count'? It gives information on the numbering (more on the 'logical' side), but the length of the piece is harder to read if we have - let's say - a split measure. Wouldn't 'count' be more robust? : see Mathieu's answer
  • 3- In the first measure, the count is not mentioned. This is not a major problem since we can easily deduce its default value is 1. Nevertheless, current json schema impose that we have at least count or id: should we reconsider this, or allow compressed versions only to break the rule? (or add counts to compressed!)

[magiraud]

The following displayed measure must mention its count

count is not musical. The user may want to rather specify its number.

[magiraud]

There should be an exception to the default values of #2:

name: idem

If a measure is fully specified with a name of 19a, the next one (when compressed / not specified) should have a name of 20a. Of course it's difficult to imagine all possible cases, but at least handle these number+letter cases.

[pythouille]

The most common cases I found are 19a followed by 19b, for second endings that were 1-measure long (in Mozart sonatas). After 19b, it is back to 20 and so on. The compressed measure map [1, 19a, 19b, 40] (default without number) would thus be [1, 19a, 19b, 20, 40] (the default you propose), a bit longer.

But yes, in the general case, your proposition is better for longer second endings or 'unfolded' repeated parts. I update it.

[pythouille]

count is not musical. The user may want to rather specify its number.

Very good point.

[johentsch]

Update: I have implemented the creation of the "default successor" as part of this PR. Specifically, this happens in the function make_default_successor() in the relevant diff).

Based on this I have added a prototype of a compression algorithm that only omits measures that have successfully been created from their predecessor (30d5491).