[PD] Limit bandwith for MIDI output / precise metro

[Nicola Pandini]

Thank you Miller!

Il 20/08/2013 03:00, Miller Puckette ha scritto:
> Seems like this should be an option... I think it's a bit late to add
> features to 0.45 but I'll stick it on my list for later.
>
> cheers
> Miller
>
> On Thu, Aug 08, 2013 at 11:03:58AM +0200, Nicola Pandini wrote:
>> Hi, I resume this old thread because I compiled pd with Miller's
>> advices to disable MIDI buffering.
>> I tested it with a patch (attached) and this configuration:
>> vkeyb-MidiOUT(ch1) -> pd-MidiIN
>> pd-MidiOUT -> pd-MidiIN
>> so, every time I play a note, I see how much time it takes to pass
>> through pd. I made this test because in my configuration I place pd
>> between my MIDI devices and synth, samplers, etc.
>> The first thing I noticed is that the latency no longer depends on
>> JACK buffer(frames/period), even with the "-jack" startup flag, and
>> the results are:
>> - With the "-jack" flag, the latency was always 1.45ms
>> - With the "-noaudio" flag, the latency was 0ms (sometimes 1.45ms)
>> Just to compare with the standard pd, the best result I achieved is
>> 1.45/2.9ms with "-noaudio".
>>
>>
>>      Nicola
>>
>>
>> Il 27/11/2012 18:50, Miller Puckette ha scritto:
>>> I believe if you edit s_midi.c and change:
>>>
>>>          if (midi_outqueue[midi_outtail].q_time <= midirealtime)
>>>
>>> to
>>>
>>> 	if (1)
>>>
>>> and
>>>
>>>          if (midi_inqueue[midi_intail].q_time <= logicaltime)
>>>
>>> also to
>>>
>>> 	if (1)
>>>
>>> that will make it fast-as-possible.  The queueing code should probably
>>> be surrounded by an ifdef to make this easier (perhaps someday...)
>>>
>>> cheers
>>> M
>>>
>>> On Tue, Nov 27, 2012 at 06:23:15PM +0100, Cyrille Henry wrote:
>>>> Is there a way to bypass all of this?
>>>> my pd usage usually imply sending and receiving as fast as possible.
>>>> sending delay usually annoy me.
>>>> cheers
>>>> c
>>>>
>>>>
>>>> Le 27/11/2012 18:06, Miller Puckette a écrit :
>>>>> Pd tries to time-stamp MIDI on input and tries to delay sending MIDI output
>>>>> until the correct time; but Pd's accuracy in doing this is limited by the
>>>>> fact that it can't input or output MIID while it is either sleeping or running
>>>>> (only when the scheduler polls for what-to-do-next after either a task or a
>>>>> sleep has finished.)
>>>>>
>>>>> It would be more accurate for Pd to rely on either software interrupts or even
>>>>> better on some underlying OS time-tagging mechanism (for instance by exploiting
>>>>> whatever portmidi does).  But I have to admit I've never treated this as a high
>>>>> priority (which one might take as an implied value judgement about MIDI).
>>>>>
>>>>> cheers
>>>>> Miller
>>>>>
>>>>> On Tue, Nov 27, 2012 at 11:44:06AM +0100, Cyrille Henry wrote:
>>>>>> Le 27/11/2012 10:36, IOhannes m zmoelnig a écrit :
>>>>>> ...
>>>>>>> with MIDI, Pd doesn't do any buffering and no synchronisation to some
>>>>>>> external clock is done, so messages appear in bursts which you notice
>>>>>>> as a inaccurate timing.
>>>>>> There is 1 strange thing however : pd did some kind of buffering with midi, in order to synchronise with audio out.
>>>>>> if you configure 100ms audio latency, then a midi loop will be between 100 and 105ms.
>>>>>> with 10ms audio buffer out, the midi loop is between 10 and 15ms.
>>>>>> but this buffer should not change anything on timing except adding latency.
>>>>>> cheers
>>>>>> c
>>>>>>
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>> #N canvas 96 143 300 152 10;
>> #X obj 79 68 timer;
>> #X obj 79 48 bng 15 250 50 0 empty empty empty 17 7 0 10 -262144 -1
>> -1;
>> #X obj 79 88 nbx 10 30 -1e+37 1e+37 0 0 empty empty empty 0 -8 0 20
>> -262144 -1 -1 1.45125 256;
>> #X obj 106 48 bng 15 250 50 0 empty empty empty 17 7 0 10 -262144 -1
>> -1;
>> #X obj 1 90 noteout 3;
>> #X obj 106 3 notein 3;
>> #X obj 1 2 notein 1;
>> #X connect 0 0 2 0;
>> #X connect 1 0 0 0;
>> #X connect 3 0 0 1;
>> #X connect 5 0 3 0;
>> #X connect 6 0 1 0;
>> #X connect 6 0 4 0;
>> #X connect 6 1 4 1;
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>> UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list


-- 
Nicola