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Re: [Guidolib-devel] API for score query
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From: Arshia C. <ars...@an...> - 2016-06-30 13:17:07
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Dominique et al. You are totally right about the ambiguity of querying the “beat duration” of a GuidoDate, which in the end will be application-specific. I suggest, to start with, to enable the query of the time-signature at a given position in the score. This way, each coder can do the translation as needed. If you can enable a method like this as you suggested in an earlier email (similar to GuidoPage stuff) it’d be wonderful for us. Bests, Arshia > On 28 Jun 2016, at 13:55, Dominique Fober <fo...@gr...> wrote: > > >> Le 27 juin 2016 à 18:45, Jonathan Aceituno <joi...@gm...> a écrit : >> >> Hi all, >> >> Chiming in… >> >> Ultimately, we would like to be able to express time locations as a number of beats from the beginning of the score, as well as switch back and forth between this representation and GuidoDates. I found no trace of such representation in GuidoLib. > > Right, this is not provided by the library. > Actually the problem is not trivial and the semantic of conversion from date to beat (and the reverse) should be clarified: > > - what convention if no meter is present? should a default beat value be used (e.g. a quarter note)? > > - how to represent dates that are not on a beat? (e.g. date 1/8 in a “4/4” meter). Should the beat be expressed using integer of floating point values ? with the former, conversion to and from are not reversible: date 3/8 in a “4/4” meter is on beat 2 but beat 2 is date 1/4, with the latter, conversions are ‘more’ reversible but face precision issues: date 1/12 is on beat 1.33333… but there is no guaranty that beat 1.3333… converts to date 1/12. Thus date to beat conversion could be an integer value + a rational to express the remainder. > > - is there any unambiguous convention to determine the beat for a given meter? it’s clear for meter like “4/4” but what about exotic time signature: e.g. 15/16 or 3+2+1/8. Actually, with a compound form like 3+2+1/8, I would say that beats are 3/8 + 1/4 + 1/8 but with 3+2+1/4, I would say that the beat is 1/4. Measure subdivision may denotes beats but not necessary. The grouping of notes may also denotes the beat. And sometimes grouping is purely conventional (like with 3/8, 6/8, … meters). It seems to me that the only clear strategy would be to use the denominator as beat unit, but is it always usable in a musical context? > >> >> As I get it, to get a beat-based time location for a given GuidoDate, we would have to get a specific GRVoice, and then iterate over its events, noting changes in meter along the way for those whose AR is a ARMeter, and accumulating durations converted to beats using the most recent meter information, up until the event's getRelativeTimePosition() corresponds to the one we'd like. Performing the reciprocal operation (getting a GuidoDate for an event whose beat-based time location is known) would follow a similar pattern. > > Seems reasonable. And how do you determine the beat from the meter? > > >> I'd also use a similar pattern to access to other score parameters (without the "accumulating" part), but maybe there's a better way? >> >> Thanks, >> Jonathan Aceituno >> >>> Hi Arshia, >>> >>> Actually, there is a minimal API to query a score, see at: >>> >>> http://guidolib.sourceforge.net/doc/guidolib/group__Pages.html <http://guidolib.sourceforge.net/doc/guidolib/group__Pages.html> >>> ; >>> It could be easily extended to provide more information e.g. something like GuidoGetMeterAt (int voicenum, const GuidoDate &date). >>> Any other useful contextual information that could be retrieved (while browsing a score up to a given date)? e.g a more general function to retrieve the meter, the current key signature, etc. >>> Any comment and proposal are welcome. >>> >>> Cheers, >>> — >>> Dominique >>> >>> >>>> Le 26 juin 2016 à 21:20, Arshia Cont <arshiacont@...> a écrit : >>>> >>>> Hello all and thanks for the great work on GuidoLib! >>>> >>>> I am wondering if there is any API for query of score parameters (such as Meter) from a specific location in the score. Basically, I need to know what is the Meter at a specific location in a rendered score. I see ARMeter and GRMeter classes but can’t seem to easily figure out how I can Get those stuff. >>>> >>>> Any hints would be appreciated. >>>> >>>> Cheers, >>>> >>>> >>>> Arshia Cont >>>> ------------------------------------------------------------------------------ >>>> Attend Shape: An AT&T Tech Expo July 15-16. Meet us at AT&T Park in San >>>> Francisco, CA to explore cutting-edge tech and listen to tech luminaries >>>> present their vision of the future. This family event has something for >>>> everyone, including kids. Get more information and register today. >>>> >>> http://sdm.link/attshape >>> >>>> _______________________________________________ >>>> Guidolib-devel mailing list >>>> Guidolib-devel@... >>>> >>> https://lists.sourceforge.net/lists/listinfo/guidolib-devel >> >> ------------------------------------------------------------------------------ >> Attend Shape: An AT&T Tech Expo July 15-16. Meet us at AT&T Park in San >> Francisco, CA to explore cutting-edge tech and listen to tech luminaries >> present their vision of the future. This family event has something for >> everyone, including kids. Get more information and register today. >> http://sdm.link/attshape >> _______________________________________________ >> Guidolib-devel mailing list >> Gui...@li... >> https://lists.sourceforge.net/lists/listinfo/guidolib-devel > > > ------------------------------------------------------------------------------ > Attend Shape: An AT&T Tech Expo July 15-16. Meet us at AT&T Park in San > Francisco, CA to explore cutting-edge tech and listen to tech luminaries > present their vision of the future. This family event has something for > everyone, including kids. Get more information and register today. > http://sdm.link/attshape > _______________________________________________ > Guidolib-devel mailing list > Gui...@li... > https://lists.sourceforge.net/lists/listinfo/guidolib-devel |
