On 10-06-25 02:02 PM, Ralf Mardorf wrote: > Hi :) > > I guess no answer is an answer :D. > Not necessarily. You could be asking the wrong question and or in the wrong place.
> There are several ways to program for asynchronous serial interfaces, > but there's only one way regarding to real time MIDI. > > When I programmed on Assembler in the 80ies I directly talked to the > UART, and request CTS/RTS for every single byte. > > It's also possible not to use CTS/RTS for every single byte, but than > you need to add headroom for the time. While it wouldn't be such a > drama, if 1ms headroom would be 1ms, it's a drama because for such a > long time a lot of IRQs are able to produce jitter, but a constant > latency. > > I guess the MIDI coders for Linux did a bad job. I might be wrong, but > as I said before, getting no answer is getting an answer :(. I would hesitate to jump to this conclusion if I were you. I would also rephrase this. Saying someone did a bad job but providing no real proof is not usually a successful strategy in the open source world. Also getting no answer may indicate a completely different problem. > Hopefully I'm just paranoid and wrong ;). I don't think paranoia is the right word. > > Cheers! > > Ralf > > -------- Forwarded Message -------- > From: Ralf Mardorf <[email protected]> > To: Paul Davis <[email protected]> > Cc: James Morris <[email protected]>, Linux Audio Developers > <[email protected]>, 64studio-users > <[email protected]> > Subject: Re: [LAD] basic MIDI note-on/note-off questions > Date: Fri, 25 Jun 2010 15:51:13 +0200 > > On Fri, 2010-06-25 at 15:36 +0200, Ralf Mardorf wrote: >> On Fri, 2010-06-25 at 14:38 +0200, Ralf Mardorf wrote: >>> On Fri, 2010-06-25 at 08:29 -0400, Paul Davis wrote: >>>> On Fri, Jun 25, 2010 at 6:55 AM, James Morris <[email protected]> wrote: >>>>> Hi, >>>>> >>>>> I keep getting surprised at some of the most basic problems I run >>>>> into... This time, processing order. >>>> >>>> just remember that in "real" MIDI, nothing can be simultaneous. its a >>>> serial protocol without timestamps. with traditional serial MIDI, the >>>> time interval between bits and bytes is also fixed, creating a fixed >>>> minimal interval between any two note on/off messages. >>> >>> In addition, the UART gives information about being ready to send. It's >>> not fixed to e.g. 1ms. There's a register giving this information. >> >> Note, there's nothing fixed, the limitation is just for the max Baud >> MIDI is able to do. Regarding to the term 'fixed' UART is for 'Universal >> Asynchronous Receiver Transmitter', the important word is >> 'Asynchronous'. We are talking about microseconds, taking care about the >> CTS and RTS registers. Regarding to all that MIDI jitter, I wonder if >> ALSA seq, might has to do with it. I don't know, perhaps there are >> issues for USB specifications, but maybe there's something bad for this >> 'timestamp' routs. >> >> *?* >> >> I programmed on Assembler directly using the UART and there never was >> jitter. >> >> Could this be a reason for MIDI jitter using Linux or has it nothing to >> do with it? Because, at the other hand there's no jitter internal the >> studio in the box. >> >> *?* >> >> Ralf > > I can't remember, perhaps CTS and RTS are flags in one register and > maybe they have other acronyms ;), anyway, this is the important stuff. > Pedro Lopez-Cabanillas did post the technical specifications. > > > _______________________________________________ > 64studio-users mailing list > [email protected] > http://lists.64studio.com/mailman/listinfo/64studio-users
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