Re: [Hydrogen-devel] about the sequencer model in H2

[Comix <co...@gm...>]

On 6/26/07, Jakob Lund <jl...@im...> wrote:
> Dear Drumheads.
HI Jakob

> I wrote two small patches for Hydrogen previously. With a classical "scratch
> your own itch" approach to development, I would like try fixing some of the
> problems that I'm having using the program, but are not on the roadmap that
> Alex laid out. Perhaps it seems like I'm taking my hands too full --- but
> really, I don't think It's that bad, *and* if I could get it to work, it'd be
> dead cool (H)
>
> I'll need some tips along the way though, and it would be nice to get feedback
> before I start to write code! Here's what it's all about:
>
> My first interest in Hydrogen is the timing and synchronization with other
> JACK apps --- Ardour is, of course, the first reference when it comes to
> JACK, and another one I really want to use together with Hydrogen is
> Freewheling ( a wierd / wonderful live looping application ). The first
> patch I wrote for Hydrogen already made it possible to accept changes in tempo
> and song position from the JACK transport system, and that seems to work o.k.
> right now, at least with Ardour.
>
> Along the same line, I would like to try to enable Hydrogen to *send* these
> messages to other JACK apps ( in JACK, an application can be either `slave'
> or `timebase master'. Hydrogen acts as `slave' when the `Jack Transport'
> button is active, and I would like to add a `master' option as well ) but
> this is when I get into some problems that I think have to do with the
> *fundamental design of the timeline* in Hydrogen, and, as far as I can tell,
> the internal representation of this timeline will have to change
> fundamentally, in order for me to succeed in adding the extra option...
>
> The problem is that Hydrogen doesn't really know the length of a `bar'... It
> just knows the Patterns and PatternGroups. The latter are collections of
> Patterns that start at the same time, and they are the columns in the "song
> editor"  part of the UI. If every pattern is 4 beats long, and the song is in
> 4/4, it works great, and the PatternGroups are the barlines --- I'm guessing
> this is what happens in 95% of the use cases.
>
> The trouble start when:
> * Patterns of different length are inserted in the same PatternGroup. Then the
> behaivour of the program seems a bit random... It doesn't crash or make ugly
> noise, but some patterns are cut off, or silence is inserted, somehow.
> * If there is a two-bar pattern in one PatternGroup, and a one-bar pattern in
> the next, the two-bar pattern only takes up one `bar' in the UI, which, I
> think, seems illogical and buggy...
>
> To remedy all this, I *just about* figured out a way of storing the starting
> times of patterns in a song in a way that it's o.k. if patterns are not the
> same length, and one pattern can start in the middle of another one playing.
> AND the sequencer will know which notes / patterns to play at any given time.
>
> When I start messing with all this, the entire program will of course stop
> working at first, and It'll have to be repaired everywhere where the timeline
> information is accessed... What I fear the most is the parts of the program
> that I *don't know* interact with the timeline. I foresee trouble in these
> three places:
>
> 1. The UI, where patterns are inserted into the song
> 2. The Sequencer, that plays each note from each pattern in the song and
> 3. The file format writer and reader, that also need to know the song
> structure!!
>
> I want to know if I missed any? I also wonder if anyone is up to attacking
> this, or at least giving me some hints -- I guess there are plenty of other
> things to do before the long-awaited 9.4 release!!
>
> I think that making the changes I suggest could make Hydrogen a more musical
> program, and also make the code easier to maintain, and maybe even faster.

I'm too sleepy (1:00 am) now to answer you :) You're right, hydrogen
internals are a bit too restrictive about that and there's the need to
introduce the concepts of tempo and bar lenght.

Tomorrow I'll write more...

Good night drummers!
-- 
Alessandro <Comix> Cominu

http://comix.hydrogen-music.org